Volume 13 - Corrosion Part 18 ppsx

57. A. Schulman, H.A.B. Linke, T.K. Vaidyanathan, Tarnish of Dental Alloys by Oral Microorganisms,
J.
Dent. Res., Vol 63, 1984, IADR No. 55
58.
M. Stern and E.D. Weisert, Experimental Observation on the Relation Between Polarization Resistance
and Corrosion Rate, Proc. ASTM, Vol 59, 1959, p 1280-1291
59. M. Marek, The Corrosion of Dental Materials, in Corrosion: Aqueous Processes and Passive Films,
Vol
23, Treatise on Materials Science, J.C. Scully, Ed., Academic Press, 1983, p 331-394
60.
M. Bergman, O. Ginstrup, and B. Nilsson, Potentials of and Currents Between Dental Metallic
Restorations, Scand. J. Dent. Res., Vol 90, 1982, p 404-408
61. K. Nilner, P
O. Glants, B. Zoger, On Intraoral Potential and Polarization Measurements of Metallic
Restorations, Acta Odontol. Scand., Vol 40, 1982, p 275-281
62. J.M. Mumford, Electrolytic Action in the Mouth and Its Relationship to Pain, J. Dent. Res.,
Vol 36, 1957,
p 632-640
63. C.P. Wang Chen and E.H. Greener, A Galvanic Study of Different Amalgams, J. Oral Rehab.,
Vol 4,
1977, p 23-27
64. R. Soremark, G. Freedman, J. Goldin, and L. Gettleman, Structure and Microdistribution of Gold Alloys
,
J. Dent. Res., Vol 45, 1966, p 1723-1735
65. D.B. Boyer, K. Chan, C.W. Svare, The Effect of Finishing on the Anodic Polarization of High-
Copper
Amalgams, J. Oral Rehab., Vol 5, 1978, p 223-228
66. G. Palaghias, Oral Corrosion Inhibition Processes, Swed. Dent. J., Supp 30, 1985
67.
H.J. Mueller and A. Edahl, The Effect of Exposure Conditions Upon the Release of Soluble Copper and
Tin From Dental Amalgams, Biomater., Vol 5, 1984, p 194-200

68. H.J. Mueller and R.M. Barrie, Intraoral Corrosion of Copper-Aluminum Alloys, J. Dent. Res.,
Vol 64,
1985, IADR No. 1753
69. G.N. Jenkins, The Physiology and Biochemistry of the Mouth, 4th ed., Blackwell, 1978, p 284-359
70. H.J. Mueller and E.H. Greener, Polarization Resistance of Surgical Materials in Ringer's Solution,
J.
Biomed. Mater. Res., Vol 4, 1970, p 29-41
71.
E.J. Sutow, S.R. Pollack, and E. Korostoff, An In Vitro Investigation of the Anodic Polarization and
Capacitance Behavior of 316-L Stainless Steel, J. Biomed. Mater. Res., Vol 10, 1976, p 671-693
72. H.J. Mueller, The Binding of Corroded Metallic Ions to Salivary-Type Proteins, Biomater.,
Vol 4, 1983, p
66-72
73. J.R. Strub, C. Eyer, N.K. Sarkar, Microstructure and Corrosion of a Low-Gold Casting Alloy,
J. Dent.
Res., Vol 63, 1984, IADR No. 793
74. M.P. Keenan, Effects of Gold Finishing on Plaque Retention, J. Dent. Res.,
Vol 56, 1977, IADR No.
121(B)
75. C.W. Svare, G. Belton, and E. Korostoff, The Role of Organics in Metallic Passivation, J. Biomed.
Mater.
Res., Vol 4, 1970, p 457-467
76. G.C.F. Clark and D.F. Williams, The Effects of Proteins on Metallic Passivation, J. Biomed. Mater. Res.,

Vol 16, 1982, p 125-134
77. S.A. Brown and K. Merritt, Electrochemical Corrosion in Saline and Serum, J. Biomed. Mater. Res.,
Vol
14, 1980, p 173-175
78. S.A. Brown and K. Merritt, Fretting Corrosion in Saline and Serum, J. Biomed. Mater. Res.,
Vol 15, p

479-488
79.
H.J. Mueller, The Effect of Electrical Signals Upon the Adsorption of Plasma Proteins to a High Cu Alloy,
in Biomaterials: Interfacial Phenomena and Applications,
S.L. Cooper and N.A. Peppas, Ed., ACS
monograph series 199, American Chemical Society, 1982
80.
R.C. Salvarezza, M.E.L. de Mele, H.H. Videla, and F.R. Goni, Electrochemical Behavior of Aluminum in
Human Plasma, J. Biomed. Mater. Res., Vol 19, 1985, p 1073-1084
81. H. Hero and L. Niemi, Tarnishing In Vivo of Ag-Pd-Cu-Zn, J. Dent. Res., Vol 65, 1986, p 1303-1307
82.
H. Do Duc and P. Tissot, Rotating Disc and Ring Disc Electrode Studies of Tin in Neutral Phosphate
Solution, Corros. Sci., Vol 19, 1979, p 191-197
83. I.D. Mandel, Relation of Saliva and Plaque to Caries, J. Dent. Res., Vol 53, 1974, p 246
84.
T. Ericson, K.M. Pruitt, H. Arwin, and I. Lunstrom, Ellipsometric Studies of Film Formation on Tooth
Enamel and Hydrophilic Silicon Surfaces, Acta Odontol. Scand., Vol 40, 1982, p 197-201
85. R.E. Baier and P
O. Glantz, Characterization of Oral In Vivo Films Formed on Different Types of Solid
Surfaces, Acta Odontol. Scand., Vol 36, 1978, p 289-301
86. K. Skjorland, Auger Analysis of Integuments Formed on Different Dental Filling Materials In Vivo,
Acta
Odontol. Scand., Vol 40, 1982, p 129-134
87.
K. Hannesson Eggen and G. Rolla, Gel Filtration, Ion Exchange Chromatography and Chemical Analysis
of Macromolecules Present in Acquired Enamel Pellicle (2-hr), Scand. J. Dent. Res., Vol 90, 1982, p 182-
188
88.
A. Bennick, G. Chau, R. Goodlin, S. Abrams, D. Tustian, and G. Mandapallimatam, The Role of Human
Salivary Acidic Proline-Rich Proteins in the Formation of Acquired Dental Pellicle

In Vivo and Their Fate
After Adsorption to the Human Enamel Surface, Arch. Oral Biol., Vol 28, 1983, p 19-27
89. T. Sonju and P
O. Glantz, Chemical Composition of Salivary Integuments Formed In Vitro on Solids with
Some Established Surface Characteristics. Arch. Oral Biol., Vol 20, 1975, p 687-691
90. D.I. Hay, The Adsorption of Salivary Proteins by Hydroxyapatite and Enamel, Arch. Oral Biol.,
Vol 12,
1967, p 937-946
91. G. Rolla, Formation of Dental Integuments Basic Chemical Considerations, Swed. Dent. J.,
Vol 1, 1977,
p 241-251
92.
A.C. Juriaanse, M. Booij, J. Arends, and J.J. Ten Bosch, The Adsorption In Vivo of Purified Salivary
Proteins on Bovine Dental Enamel. Arch. Oral Biol., Vol 26, 1981, p 91-96
93. H.J. Mueller, Differential Scanning Calorimetry of Adsorbed Protein Films, in
Transactions of the 13th
Annual Meeting Society of the Biomaterials, 1987
94.
R D. Norman, R.V. Mehra, and M.L. Schwartz, The Effects of Restorative Materials on Plaque
Composition, J. Dent. Res., Vol 50, 1971, IADR No. 162
95. J.J. Tuccillo and J.P. Nielson, Microprobe Analysis of an In Vivo Discoloration, J. Prosthet. Dent.,
Vol
31, 1794, p 285-289
96. J.J. Tuccillo and J.P. Nielson, Observation of Onset of Sulfide Tarnish on Gold-Base Alloys,
J. Prosthet.
Dent., Vol 25, 1971, p 629-637
97.
R.P. Lubovich, R.E. Kovarik, and D.L. Kinser, A Quantitative and Subjective Characterization of
Tarnishing in Low-Gold Alloys, J. Prosthet. Dent., Vol 42, 1979, p 534-538
98. G.W. Marshall, N.K. Sarkar, and E.H. Greener, Detect

ion of Oxygen in Corrosion Products of Dental
Amalgam, J. Dent. Res., Vol 54, 1975, p 904
99.
H. Otani, W.A. Jesser, and H.G.F. Wilsdorf, The In Vivo and the In Vitro Corrosion Products of Dental
Amalgam, J. Biomed. Mater. Res., Vol 7, 1973, p 523-539
100.

A.B. Burse, M.L. Swartz, R.W. Phillips, and R.W. Oykema, Comparison of the In Vivo and In Vitro
Tarnish of Three Gold Alloys, J. Biomed. Mater. Res., Vol 6, 1972, p 267-277
101.

B.R. Laing, S.H. Bernier, Z. Giday, and K. Asgar, Tarnish and Corrosion of Noble Metal Alloys,
J.
Prosthet. Dent., Vol 48, 1982, p 245-252
102.

H. Hero and J. Valderhaug, Tarnishing In Vivo and In Vitro of a Low-
Gold Alloy Related to Its Structure,
J. Dent. Res., Vol 64, 1985, p 139-143
103.

H. Hero and R.B. Jorgensen, Tarnishing of a Low-Gold Alloy in Different Structural States, J. Dent. Res.,

Vol 62, p 371-376
104.

L. Gettlemen, R.F. Cocks, L.A. Darmiento, P.A. Levine, S. Wright, and D. Nathanson, Measurement of In
Vivo Corrosion Rates in Baboons and Correlations With In Vivo Tests, J. Dent. Res., Vol 1980, p 689-707

105.

L. Gettleman, C. Amman, and N.K. Sarkar, Quantitative In Vivo and In Vitro Measurement of Tarnish,
J.
Dent. Res., Vol 58, 1979, IADR No. 969
106.

Revised American Dental Association Specification No. 1 for Alloy for Amalgam, J. Am. Dent. Assoc.,

Vol 5, 1977, p 614-617
107.

Addendum to ANSI/ADA Specification No. 1 for Alloy for Amalgam, J. Am. Dent. Assoc.,
Vol 100, 1980,
p 246
108.

D.B. Mahler and J.D. Adey. Microprobe Analysis of Three High Copper Amalgams, J. Dent. Res.,
Vol 63,
1984. p 921-925
109.

J.W. Edie, D.B. Boyer, and K.C. Chjan. Estimation of the Phase Distribution in Dental Amalgams With
Electron Microprobe, J. Dent. Res., Vol 57, 1978. p 277-282
110.

J. Leitao, Surface Roughness and Porosity of Dental Amalgam, Acta Odontol. Scand., Vol 40, 1982. p 9-
16
111.

R.W. Bryant. Gamma-2 Phase in Conventional Amalgam-Discrete Clumps or Continuous Network

A
Review, Aust. Dent. J., Vol 29, 1984. p 163-167
112.

L.B. Johnson, X-Ray Diffraction Evidence for the Presence of (Ag-Hg) in Dental Amalgam,
J. Biomed.
Mater. Res., Vol 1, 1967, p 285-297
113.

S.J. Marshall and G.W. Marshall. Jr., Time-Dependent Phase Changes in Cu-Rich Amalgams,
J. Biomed.
Mater. Res., Vol 13, 1979. p 395-406
114.

Revised ANSI/ADA Specification No. 5 For Dental Casting Gold Alloy. J. Am. Dent. Assoc.,
Vol 104,
1981. p 70
115.

J.P. Moffa, Alternative Dental Casting Alloys, Dent. Clin. N. Am., Vol 27, 1983. p 194-200
116.

R.M. German, Precious-Metal Dental Casting Alloys, Int. Met. Rev., Vol 27, 1982. p 260-288
117.

K. Yasuda and K. Hisatsune, The Development of Dental Alloys Conserving Precious Metals: Im
proving
Corrosion Resistance by Controlled Aging, Int. Dent. J., Vol 33, 1983
118.

D.L. Smith, Dental Casting Alloys, Technical and Economic Considerations in the USA, Int. Dent. J.,
Vol
33, 1983, p 25-34
119.

S.A. Aquilino and T.D. Taylor, Prosthodontic Laboratory Survey, J. Prosthet. Dent., Vol 53, 1984, p 879-
885
120.

H. Hero, Tarnishing and Structures of Some Annealed Dental Low-Gold Alloys, J. Dent. Res.,
Vol 63,
1984. p 926-931
121.

L. Niemi and H. Hero, Structure, Corrosion, and Tarnishing of Ag-Pd-Cu Alloys, J. Dent. Res.,
Vol 64,
1985, p 1163-1169
122.

R.C. Craig, H.J. Skesnick, and F.A. Peyton, Application of 17-
7 Precipitation Hardenable Stainless Steel
in Dentistry, J. Dent. Res., Vol 44, 1965, p 587-595
123.

S. Civjan, E.F. Huget, and L.B. de Simon, Effects of Laboratory Procedures on 55-Nitinol, J. Dent. Res.,

Vol 52, 1973, IADR No. 51
124.

A.J. Goldberg and C.J. Burstone, an Evaluation of Beta-

Stabilized Titanium Alloys for Use in Orthodontic
Appliances, J. Dent. Res., Vol 57, 1978, p 593-600
125.

E.F. Huget and S.G. Vermilyea, Base Metal Dental and Surgical Alloys, in
Biocompatibility of Dental
Materials, Vol IV, D.C. Smith and D.F. Williams, Ed., CRC Press, 1982, p 37-49
126.

H.F. Morris and K. Asgar, Physical Properties and Microstructure of Four New Paertial Denture Alloys,
J.
Dent. Res., Vol 57, 1978, IADR No. 218
127.

A.T. Kuhn, The Corrosion of Metals and Alloys Used in Density, in
Restoration of the Partially Dentate
Mouth, J.F. Bates, D.J. Neill, and H.W. Preiskel, Ed., Quintessence Publishing, 1984, p 160-175
128.

K. Asgar and F.C. Allan, Microstructure and Physical Properties of Alloys for Partial Denture Castings,
J.
Dent. Res., Vol 47. 1968, p 189-197
129.

Civijan, E.F. Huget, W.L. Erhard, and G.J. Vaccaro, Characterization of Surgical Casting Alloys,
J. Dent.
Res., Vol 50, 1971, IADR No. 584
130.

T.M. Devine and J. Wulff. Cast vs Wrought Cobalt-Chromium Surgical Implant Alloys, J. Biomed.

Mater.
Rest., Vol 9, 1975, p 151-167
131.

R.G. Craig (Chm), Section One Report, in
International Workshop on Biocompatibility, toxicity, and
Hypersensitivity to Alloy Systems Used in Dentistry.
Conference Proceedings. University of Michigan
School of Dentistry, 1985
132.

E.F. Huget and S.G. Vermilyea, Base Metal Dental and Surgical Alloys, in
Biocompatibility of Dental
Materials, Vol IV, D.C. Smith and D.F. Williams, Ed., CRC Press, 1982. p 34-49
133.

T.G. Goodall, The Metallography of Heat Treatment Effects in a Nickel-Base Casting Alloy, Aust.
Dent.
J., Vol 24, 1879, p 235-237
134.

S
. Winkler, H.F. Morris, and J.M. Monteiro, Changes in Mechanical Properties and Microstructure
Following Heat Treatment of a Nickel-Chromium Alloy, J. Prosthet. Dent., Vol 52. 1984, p 821-827
135.

K. Asgar and F.C. Allan. Microstructure and Physical Properties of Alloys of Partial Denture Castings,
J.
Dent. Res., Vol 47, 1968, p 189-197
136.

K. Asgar and F.A. Peyton, Effect of Microstructure on the Physical Properties of Cobalt-Base Alloys,
J.
Dent. Res., Vol 40, 1961, p 63-72
137.

Revised ANSI/ADA Specification No. 14, Dental Base Metal Casting Alloys, J. Am. Dent. Assoc.,
Vol
105, 1982, p 686-687
138.

H.F. Morris and K. Asgar, Physical Properties and Microstructure of Four New Commercial Partial
Denture Alloys, J. Prosthet. Dent., Vol 33, 1975, p 36-46
139.

H. Mohammed and K. Asgar, A New Dental Superalloy System, J. Dent. Res., Vol 53, 1973, p 7-14
140.

J.F. Bates and A.G. Knapton, Metal and Alloys in Dentistry, Int. Met. Rev., Vol 22 (No. 215), 1977, p 39-
60
141.

R.M. Waterstrat, N.W. Rupp, and O. Franklin, Production of a Cast Titanium-Base Partial Denture,
J.
Dent. Res., Vol 57A, 1978. IADR No. 717
142.

M. Taira, J.B. Moser, and E.H. Greener, Mechanical Properties of Cast Ti Alloys for Dental Uses,
J. Dent.
Res., Vol 65, 1986, IADR No. 603

143.

E.F.I. Roberts and K.M. Clarke, The Colour Characteristics of Gold Alloys, Gold Bull., Vol 9, 1979, p 9-
19
144.

R.M. German, M.M. Guzowski, and D.C. Wright, Color and Color Stability as Alloy Design Criterion,
J.
Met., Vol 32, 1980, p 20-27
145.

D.J.L. Treacy and R.M. German, Chemical Stability of Gold Dental Alloys, Gold Bull.,
Vol 17, 1984, p
46-54
146.

Coroso, Jr., R.M. German, and H.D. Simmons, Jr., Tarnish Evaluation of Gold-Based Dental Alloys,
J.
Dent. Res., Vol 64, 1965
147.

R.M. German. The Role of Microstructure in the Tarnish of low Gold alloys, Metallography,
Vol 14,
1981, p 253-266
148.

R.M. German. D.C. Wright, and R.F. Gallant, In Vitro Tarnish Measurements on Fixed Prosthodontic
Alloys, J. Prosthet. Dent., Vol 47, 1982. p 399-406
149.

D.C. Wright and R.M. German, Quantification of Color and Tarnish Resistance of Dental Alloys.
J. Dent.
Res., Vol 58A, 1979. IADR No. 975
150.

D.A. Nitkin and K. Asgar, Evaluation of Alternative Alloys to Type III Gold for Use in Fixed
Prosthodontics, J. Am. Dent. Assoc., Vol 93, 1976, p 622-629
151.

S. Civjan, E.F. Huget, and J. Marsden, Characterization of Two High-Fusing Gold Alloys, J. Dent. Res.,

Vol 51, 1972, IADR No. 222
152.

J.F. Bates and A.G. Knapton, Metal and Alloys in Dentistry, Int. Met. Rev., Vol 22, 1982, p 39-60
153.

S. Civjan, E.F. Huget, N.N. Dvivedi, and H.E. Cosner, Jr., Characterization of Two Au-Pd-Ag Alloys,
J.
Dent. Res., Vol 52, 1973, IADR No. 46
154.

E.F. Huget, S.G. Vermilyea, and J.M. Vilca, Studies on White Crown-and-Bridge Alloys, J. Dent. Res.,

Vol 57, 1978, IADR No. 722
155.

P.F. Mezger, M.M.A. Vrijhoef, and E.H. Greener, Corrosion Resistance of Three High Palladium Alloys,
Dent. Mater., Vol 1, 1985, p 177-179
156.

M.M.A Vrijhoef and J.M. van der Zel, Oxidation of Two High-Palladium PFM Alloys, Dent. Mater.,
Vol
1. 1985, p 214-218
157.

R.L. Bertolotti, Selection of Alloys for Today's Crown and Fixed Partial Denture Restorations,
J. Am.
Dent. Assoc., Vol 108, 1984, p 959-966
158.

J.J. Tuccillo, Compositional and Functiona
l Characteristics of Precious Metal Alloys for Dental
Restorations, in Alternatives to Gold Alloys in Dentistry,
T.M. Valega, Ed., Conference Proceedings.
DHEW Publication (NIH) 77-1227, Department of Health, Education, and Welfare, 1977
159.

P.J. Cascone, Phase Relations of the Palladium-Base, Copper, Gallium, Indium Alloy System,
J. Dent.
Res., Vol 63, 1984, IADR No. 563
160.

M.M.A. Vrijhoef, Oxidation of Two High-Palladium PFM Alloys, Dent. Mater., Vol 1, 1985, p 214-18
161.

Sumithra, T.K. Vaidyanathan, S. Sastri, and A. Prasad, Chloride Corrosion of Recent Commercial Pd-
Based Alloys. J. Dent. Res., Vol 62, 1983, IADR No. 346
162.

S.M. Paradiso, Corrosion Evaluation of Pd-Cu-Ga, J. Dent. Res., Vol 43, 1984, IADR No. 43
163.

P.R. Mezger, M.M.A. Vrijhoef, and E.H. Greener, Corrosion Resistance of Three High-
Palladium Alloys,
Dent. Mater., Vol 1, 1985, p 177-180
164.

Oden and H. Hero, The Relationship Between Hardness and Structure of Pd-Cu-Ga Alloys, J. Dent. Res.,

Vol 65, 1986, p 75-79
165.

J.R. Mack
ert, Jr., E.E. Parry, and C.W. Fairhurst, Oxide Metal Interface Morphology Related to Oxide
Adherence, J. Dent. Res., Vol 63, 1984, IADR No. 405
166.

G. Baron, Auger Chemical Analysis of Oxides on Ni-Cr Alloys, J. Dent. Res., Vol 63, 1984, p 76-80
167.

D
.L. Menis, J.B. Moser, and E.H. Greener, Experimental Porcelain Compositions for Application to Cast
Titanium, J. Dent. Res., Vol 65, 1986, IADR No. 1565
168.

ANSI/ADA Specification No. 32, New American Dental Association Specification No. 32 for Orthodon
tic
Wires Not Containing Precious Metals, J. Am. Dent. Assoc., Vol 95, 1997, p 1169-71
169.

P.J. Brockhurst, Base Metal Wires for Gold Alloy Soldering to Cast Cobalt-
Chromium Alloy Partial
Dentures, Aust. Dent. J., Vol 15, 1970, p 499-506
170.

M.R. Marco
tte, Optimum Time and Temperature for Stress Relief Heat Treatment of Stainless Steel Wire,
J. Dent. Res., Vol 52, 1973, p 1171-1175
171.

C.J. Burstone and J.Y. Morton, Chinese NiTi Wire A New Orthodontic Wire, Am. J. Ortho.,
Vol 87,
1985, p 445-452
172.

M. Bergman, Combinations of Gold Alloys in Soldered Joints, Swed. Dent. J., Vol 1, 1977, p 99-106
173.

C.E. Janus, D.F. Taylor, and G.A. Holland. A Microstructural Study of Soldered Connectors of Low-
Gold
Casting Alloys, J. Prosthet. Dent., Vol 50, 1983, p 657-663
174.

T.M. Devine and J. Wulff, Cast vs Wrought Cobalt-Chromium Surgical Implant Alloys, J. Biomed.
Mater.
Res., Vol 9, 1975, p 151-167
175.

H.J. Mueller and B.C. Marker, Effect of and Cl

-
Upon Product Deposition on NTD and Cupralloy,
J. Dent. Res., Vol 59, IADR N. 279, 1980
176.

H.J. Mueller, SIMS and Colorimetry of In-Vitro Sulfided Crown and Bridge Alloys, in
Fifth International
Symposium on New Spectroscopic Methods for Biomedical Research,
Battelle Laboratories and University
of Washington, 1986
177.

H. Hero, Tarnishing and Structures of Some Annealed Dental Low-Gold Alloys, J. Dent. Res.,
Vol 63,
1984, p 926-931
178.

E. Suoninen and H. Hero, Effect of Palladium on Sulfide Tarnishing of Noble Metal Alloys,
J. Biomed.
Mater. Res., Vol 19. 1985, p 917-934
179.

R. Kropp, Application of Corrosion and Tarnish Tests to Different Dental Alloys J. Dent. Res.,
Vol 65,
1986. IADR No. 197
180.

T.K. Vaidyanathan and A. Prasad, In Vitro Corrosion and tarnish Characteristics of Typical Dental Gold
Compositions, J. Biomed. Mater. Res., Vol 15, 1981. p 191-201
181.

J. Brugirard, Baigain, J.C. Dupuy, H. Mazille, and G. Monnier, Study of the El
ectrochemical Behavior of
Gold Dental Alloys, J. Dent. Res., 1973, p 838-836
182.

W. Popp, H. Kaiser, H. Kaesche, W. Bramer, and F. Sperner, Electrochemical Behavior of Noble Metal
Dental Alloys in Different Artificial Saliva Solutions, in Proceedings of
the 8th International Congress of
Metallic Corrosion, Vol 1, DECHEMA, 1981, p 76-81
183.

N.K. Sarkar, R.A. Fuys, and J.W. Stanford, The Chloride Corrosion Behavior of Silver-
Base Casting
Alloys, J. Dent. Res., Vol 58, 1979, p 1572-1577
184.

D.C. Wright,
R.M. German, and R.F. Gallant, Copper and Silver Corrosion Activity in Crown and Bridge
Alloys, J. Dent. Res., Vol 60, 1981, p 809-814
185.

T.K. Vaidyanathan and A. Prasad, In Vitro Corrosion and Tarnish Analysis of Ag-Pd Binary System,
J.
Dent. Res., Vol 60, 1981, p 707-715
186.

N. Ishizaki, Corrosion Resistance of Ag-
Pd Alloy System in Artificial Saliva: An Electrochemical Study,
J. Osaka Dent. Univ., Vol 3, 1969, p 121-133

187.

L.A. O'Brien and R.M. German, Compositional Effects on Pd-Ag Dental Alloys, J. Dent. Res.,
Vol 63,
1984, IADR No. 44
188.

N.K. Sarkar, R.A. Fuys, and J.W. Stanford, The Chloride Behavior of Silver-Base Casting Alloys
J. Dent.
Res., Vol 58, 1979, p 1572-1577
189.

L. Niemi and R.I. Holland, Tarnish and Corrosion of a Commercial Dental Ag-Pd-Cu-Au Casting Alloy,
J.
Dent. Res., Vol 63, 1984, p 1014-1018
190.

L. Niemi and H. Hero, Structure, Corrosion, And Tarnishing of Ag-Pd-Cu Alloys, J. Dent. Res.,
Vol 64,
1985, p 1163-1169
191.

J.M. Meyer, Corrosion Resistance of Ni-Cr Dental Casting Alloys, Corros. Sci., Vol 17, 1977, p 971-982
192.

R.J. Hodges, The Corrosion Resistance of Gold and Base Metal Alloys, in
Alternatives to Gold Alloys in
Dentistry, T.M. Valega, Ed., DHEW Publication (NIH) 77-1227, Department of Health, Education,
and
Welfare, 1977

193.

N.K. Sarkar and E.H. Greener, In Vitro Corrosion Resistance of New Dental Alloys, Biomater.
Med. Dev.
Art. Org., Vol 1, 1973, p 121-129
194.

H.J. Mueller and C.P. Chen, Properties of a Fe-Cr-Mo Wire J. Dent., Vol ll, 1983, p 71-79
195.

N.K. Sarkar, W. Redmond, B. Schwaninger, and A.J. Goldberg, The Chloride Corrosion Behavior of Four
Orthodontic Wires, J. Oral Rehab., Vol 10, 1983, p 121-128
196.

H.J. Mueller, Silver and Gold Solders Analysis Due to Corrosion, Quint. Int., Vol 37, 1981, p 327-337
197.

D.L. Johnson, V.W. Rinne, and L.L. Bleich, Polarization-Corrosion Behavior of Commercial Gold-
and
Silver-Base Casting Alloys in Fusayama Solution, J. Dent. Res., Vol 62, 1983, p 1221-1225
198.

A.D. Vardimon and H.J. Mueller, In V
itro and In Vivo Corrosion of Permanent Magnets in Orthodontic
Therapy, J. Dent. Res., Vol 64, 1985, IADR No. 89

Corrosion of Emission-Control
Equipment
William J. Gilbert and Robert John Chironna, Croll-Reynolds Company, Inc.

Introduction
CORROSION PROBLEMS and material selection for emission-control equipment can be difficult because of the varied
corrosive compounds present and the severe environments encountered. Therefore, a number of the more common
emission-control applications will be discussed. More detailed information on the applications is available in the
references cited at the end of this article.
Flue Gas Desulfurization
By far the most common cleaning application for flue gases is flue gas desulfurization (FGD). This section will discuss
the selection of materials of construction for FGD systems. More information on corrosion in FGD systems is available in
the section "Corrosion of Flue Gas Desulfurization Systems" of the article "Corrosion in Fossil Fuel Power Plants" in this
Volume.
These systems came into being in the late 1960s and early 1970s because of the tightening of restrictions on the release of
sulfur emissions. The oil shortage of the mid-1970s and subsequent oil price increases led to the reuse of coal in new and
renovated power plants. In virtually all cases, this meant the potential for increased sulfur emissions. Many more FGD
systems were needed.
Fuel gas desulfurization systems typically use wet scrubbing units with lime or limestone slurries for sulfur dioxide (SO
2
)
absorption. Initially, it was thought that the relatively mild pH and temperature conditions found within most of these
systems would not present a significant corrosion problem. This was soon found not to be the case. The fact that the FGD
system could constitute up to 25% of the total capital and operating expenses of the power plant made it imperative to
determine the reasons behind the failure of the material.
Environment. The gases encountered by the FGD system are hot and contain SO
2
at significant levels, some sulfur
trioxide (SO
3
) as a result of the oxidation of SO
2
at high temperatures, and fly ash. Initially, these gases may be sent to a
dry-dust collector, such as an electrostatic precipitator of fabric filter baghouse, for fly ash removal. The gases typically

enter a wet scrubber (venturi with separator) and are quenched as SO
2
is absorbed. The components that often have the
severest problems, however, are the outlet duct and stack. Here the condensates are more acidic, the gases are highly
oxygenated, and the presence of chlorides and fluorides, can cause serious corrosion problems. Nevertheless, throughout
the entire system, corrosion can occur to various degrees and because of various factors.
Corrosion Factors. Four basic factors affect the severity and type of corrosion that occurs. They are discussed below.
pH. The result of the reactions that take place within the scrubber is a slurry with a typical pH of 4 to 5. This is desirable,
because it allows for good absorption of SO
2
and is acidic enough to reduce scale formation. Local pH values as low as 1
may exist from the concentration of chlorides entering the makeup liquid with contributions from fluorides. The low-pH
conditions with the presence of chlorides and fluorides limit the use of carbon steels, stainless steels, and a number of
higher-nickel alloys (Fig. 1).

Fig. 1 Minimum levels of chloride that cause pitting and crevice corrosion in 30 days in SO
2
-
saturated chloride
solutions at 80 °C (175 °F). Source: Ref 1
Gas Saturation. The dry flue gas is not severely corrosive. However, when the gas reaches its dew point, sulfuric
(H
2
SO
4
) and sulfurous (H
2
SO
3
) acids can form. In addition, hydrochloric acid (HCl) is produced because of the presence

of hydrogen chloride (formed at the elevated temperatures of combustion) plus the condensing water vapor. Again,
significant problems arise from the use of carbon or stainless steels.
Temperature. The problems caused by temperature excursions are primarily related to the lessening of the corrosion-
resistant properties of synthetic coatings, fiberglass-reinforced plastics (FRP), and thermoplastics, possibly to the point of
complete destruction at high enough temperatures. This affects metals to a lesser extent, but can make a bordering
problem a serious one.
Erosion generally occurs as a result of fly ash within the gas impacting on a surface in a relatively dry area of the system
or the liquid slurry impinging upon a wetted surface. In either case, areas susceptible to corrosion attack are produced.
General Materials Selection. An easily overlooked but critical aspect of materials selection is the ability of the
manufacturer to construct the equipment properly with correct fabrication techniques. In particular, with regard to the use
of high-nickel alloys, the welding recommendations of alloy producers should be precisely followed to maintain the
corrosion resistance of the materials (Ref 2). This is of course true for any type of fabrication. The most careful materials
selection process can be negated by poor fabrication practices.
Metals. Where pH is neutral or higher, austenitic stainless steels (AISI types 304, 316, and 317, L grades preferred)
perform well even at elevated temperatures. If pH is as low as 4 and chloride content is low (less than 100 ppm) but
temperatures are above approximately 65 °C (150 °F) then Incoloy 825, Inconel 625, Hastelloy G-3, and alloy 904L
(UNS N08904) or their equivalents are usually acceptable. Table 1 lists compositions of alloys commonly used in FGD
systems.
Table 1 Compositions of some alloys used in FGD systems
Composition, %
(a)
Alloy
C Fe Ni Cr Mo Mn Others
Type 304L
0.03
max
bal
(b)
10.0

19.0 . . . 2.0
max
0.045 max P, 0.03 max S,and 1.00 max Si
Type 316L
0.03
max
bal 12.0

17.0 2.5 2.0
max
1.00 max Si 0.045 max P, and 0.03 max S
Type 317L
0.03
max
bal 13.0

19.0 3.5 2.0
max
1.00 max Si, 0.045 max P, and 0.03 max S
Inconel alloy
625
0.10
max
5.0
max
bal 21.5 9.0 0.50
max
0.40 max Al, 0.40 max Ti, 3.65 Nb, 0.015 max P, 0.015 max S,
and 0.50 max Si
Incoloy alloy

825
0.05 bal 42.0

21.5 3.0 1.0
max
0.8 Ti, 0.5 max Si, 0.2 max Al, 2.25 Cu, and 0.03 max S
INCO alloy G
0.05
max
19.5 bal 22.25

6.5 1.5 1.0 max Si, 2.125 Nb, 2.5 max Co, 2.0 Cu, 1.0 max W, and 0.04
max P
INCO alloy G-
3
0.15
max
19.5 bal 22.25

7.0 1.0
max
5.0 Co, 2.0 Cu 0.04 max P, 1.0 max Si, 0.03 max S, 1.5 max W,
and 0.05 max Nb + Ta
INCO alloy C-
276
0.02
max
5.5 bal 15.5 16.0

1.0

max
2.5 max Co, 0.03 max P, 0.03 max S, 0.08 max Si, and 0.35 max
V
INCO alloy
0.02 bal 25.5

21.0 4.5 2.0 1.5 Cu 1.0 max Si, 0.045 max P, and 0.035 max S
(a)
Nominal composition unless otherwise specified.
(b)
bal, balance

When chloride content is up to 0.1% and pH approaches 2, only Hastelloys C-276, G, and G-3, and Inconel 625 can be
successfully used. The other alloys mentioned above would be subjected to pitting and crevice corrosion. If a region is
encountered with pH as low as 1 and chloride content above 0.1%, one of the only successful alloys acceptable is reported
to be Hastelloy C-276 or its equivalent. In terms of metals selection, the higher the molybdenum content in an alloy, the
more severe the corrosive environment it can withstand in the FGD system (Ref 3).
Nonmetals. Fiberglass-reinforced plastics can be used in almost any application in which temperatures do not exceed
120 °C (250 °F) (preferably 95 °C, or 205 °F), regardless of whether there are high chlorides or low pHs. The best choices
would be premium grades of vinyl-ester and polyester resins. Polypropylene(PP), chlorinated polyvinyl chloride (CPVC),
and other thermoplastics can be used in such applications as mist elimination, in which temperatures are suitably low, for
example, 80 °C (175 °F) for PP. Rubber linings can also be used where temperatures are suitable and mechanical damage
can be avoided.
Waste Incineration
In a number of ways, the problems associated with materials for incinerator off-gas treatment equipment are similar to
those used for FGD systems. Depending on the wastes being burned, however, significantly higher gas temperatures as
well as more varied and more highly corrosive compounds may be encountered. Materials selection for waste incineration
parallels that for FGD systems to some extent, but can often be more demanding.
The importance of incineration for the treatment of domestic and industrial wastes has increased as the availability of
sanitary landfills has lessened and their costs have escalated. At the same time, environmental safety regulations have

limited the use of deep below-ground and sea-disposal sites for untreated wastes.
Incineration provides a viable, although not inexpensive, alternative that produces scrubbable gaseous and particulate
contaminants from a myriad of waste products. Incinerators are used to burn municipal solid wastes, industrial chemical
wastes, and sewage sludge. In general, the off-gases can be classified according to their corrosiveness in descending order
as follows: industrial chemical, municipal solid, and sewage sludge.
Industrial Chemical. These gases are characterized by extremely high temperatures (1000 °C, or 1830 °F, is not
uncommon) and the presence of halogenated compounds. In many cases, chlorinated hydrocarbons and plastics are
burned, producing HCl, chlorine, hydrogen fluoride (HF), and possibly hydrogen bromide. Some sulfur and phosphorus
compounds may also be produced.
The typical treatment systems uses a gas quench to saturate and cool the gases, a wet venturi scrubber (if particulates pose
a problem), a packed tower absorber, exhaust fan, ducting, liquid piping, and liquid recirculation pumps. Figure 2 shows a
standard system arrangement.
Because of high temperatures, the presence of
chlorides, and the fact that the gas becomes saturated
with water vapor within the quench, very few
materials can be successfully used for the quench
construction. The major problem is not uniform
attack but local pitting and crevice corrosion of many
metals. In particular, chloride stress-corrosion
cracking severely affects austenitic stainless steels.
The materials that have found to perform very well
are such high-nickel alloys as Hastelloy C-276,
Inconel 625, and titanium for the highest-temperature
cases and Hastelloy G and G-3 for slightly less severe
cases. These materials have been used in other critical
areas of the treatment system, such as fan wheels,
dampers, liquid spray nozzles, and piping. Multiple-
year service life histories have been reported with
these alloys (Ref 4.)
Refractory linings for the quench have also been used

with some success. This can sometimes prove to be a
more economical alternative to the use of high-nickel alloys. Problems do occur, however, because of attack on the
binding substances employed and on the carbon steel base material, if exposed.
Following the quench, where temperatures are typically less than 95 °C (205 °F), the major equipment (venturis, tower
shells, sump tanks, fan housings, and pump bodies) can be constructed of FRP. A premium polyester or vinyl-ester resin
can withstand even the most severe corrosive atmospheres at these milder temperatures. Even the presence of glass-
attacking fluorides would not preclude the use of FRP, given the availability of synthetic veils used to replace glass veils
within the resin layers closest to the internally exposed surfaces.
The recirculating fluids, often alkaline because of the need to scrub acidic gases, can often be handled satisfactorily by
FRP or such thermoplastics as CPVC and PP. In this case, the alkalinity is not the problem. Free chlorides and fluorides
may be present even in the most carefully operated and maintained systems.
Fiberglass-reinforced plastic ductwork is used to transport the gases in the milder-temperature areas of the system.
Because PP exhibits good resistance to most of the corrosives usually encountered, it is used for tower packing, mist
eliminators, and spray nozzles. It is a particularly good choice for environments having the potential for severe fluoride
attack. The use of rubberlined components can be successful, but the emergence of sound FRP construction has limited its
popularity.
Caution must be exercised when using plastics in the system following the quench. If the quench loses its liquid and there
are no safeguards, a major part of the downstream equipment may be destroyed. Typically, temperatures are monitored so
that an emergency cooling liquids source, possibly city water, is injected into the quench to prevent disastrous
temperature excursions if the normal liquid source is lost.
A more conservative approach that is implemented in many system designs would also use high-nickel alloy construction
for the equipment directly downstream of the quench. In any case, this question must be addressed during the design
phase of any incineration project.

Fig. 2 Schematic of a general scrubber system arrangement

Municipal Solid Waste. The by-products of solid municipal wastes can be similar to those found in chemical
incineration. The levels of the worst contaminants chlorides, for example are usually lower. The nature of the
requirements for burning these wastes, which contain large portions of cellulose, result in lower off-gas temperatures than
those for chemical incineration.

Nevertheless, corrosion problems are severe, and materials selection is not very different from that of industrial chemicals
incineration. Reference 5 provides a ranking of metals with respect to corrosion resistance on the basis of corrosion tests
in this service. In addition, Ref 6 shows the results of corrosion tests for a very wide range of alloys in six distinct system
zones.
Sewage Sludge. The burning of sewage sludge presents the least corrosive discharge of the three types under
discussion. This can be attributed to limited halogen compounds in the gas and somewhat lower temperatures (typically
315 to 650 °C, or 600 to 1200 °F.
Type 304 and 316 stainless steels are suitable for construction in most areas of the system, including the quenching area,
whether as a separate quench or part of the wet scrubber. Again, FRP, thermoplastics, and lined carbon steel can be used
in the cooler regions.
The predominant contaminants in the environment are odorous sulfur compounds, both organic (mercaptans) and
inorganic (hydrogen sulfide, H
2
S), and particulate. Chlorides can exist, but they normally originate from the water used
for makeup. Their presence sometimes requires the use of high-nickel alloys for such components as fan wheels and
pump impellers.
Erosion can be a significant problem in any of these systems. It can wear down critical moving mechanical components
and equipment walls at points of liquid and/or gas impingement and, perhaps more importantly, it can contribute to
corrosion attack.
The overall effect is not as severe as that found with FGD treatment equipment, but there are a number of areas of
concern. The venturi throat and spray nozzles can suffer some abrasion. Fan wheels and pump impellers, however,
usually the most critical areas in these systems with respect to potential problems.
The use of high-nickel alloys at these points has been noted above. Rubber lining can also be used, although generally not
on fan wheels. Fiberglass-reinforced plastic can also be fabricated with silicon carbide impregnation for increased
abrasion resistance for the internal surfaces.
Bulk Solids
Bulk solids processes include many different industries. The one thing they have in common is the need to handle dust
collection for air pollution control.
Examples of this type of process include grain handling, foundries, coal handling, pneumatic conveying systems, and
spray-drying systems. In every case, fine particles of dust can become entrained in the exhaust air and must be removed

prior to discharge of the air. The three most common types of dust collection equipment are fabric filters, electrostatic
precipitators, and wet scrubbers.
The selection of materials of construction does vary with the industry, but the dust handled is generally not severely
corrosive. Carbon steel is the most common material of construction.
In selecting a dust collector, the most common construction for the vessel itself is steel, but the fabric used in the
collection varies greatly. The manufacturers of fabric filters will have the greatest experience with selection for a specific
application. Their expertise should be used in evaluating the relative initial maintenance cost for alternate fabrics.
Typically, most bulk-handling applications can be managed with the use of PP for the filter bags. Currently, the cost of PP
filter bags is close to that cotton filter bags. The low initial cost of PP makes it a versatile material of construction for this
application. It does not rot when it becomes wet and offers relatively good corrosion resistance. The primary limitation is
temperature.
Fans and stacks located downstream from a fabric filter are normally constructed of carbon steel. Because most of the
dust has already been collected before it reaches this point, abrasion is not a major concern in the design of the
downstream components.
Where extremely high performance is required, an electrostatic precipitator can be applied to a bulk solids application.
This normally occurs in relatively dry services with inert particles. As such, the materials of construction are typically
carbon steel.
Wet scrubbers are often used where the solids being handled are more reactive. For example, if there is a concern over the
potential for an explosive mixture of the dust with air, the wet scrubber eliminates this problem. Wet scrubbers are also
versatile and can simultaneously remove dust and gas.
Where scrubbers are applied, their low initial cost is partially by the need to recirculate a water-base solution. Care must
be taken to ensure that this solution does not become corrosive or, if it does, to select the proper materials of construction
for this specific case.
Commonly, general nuisance dust that is collected by a scrubber does not cause a direct corrosion problem. Instead, the
problems arise because of the need to minimize the wastewater from the scrubber. For example, if the inlet is at ambient
conditions, the scrubber will evaporate 122 L/h (31.8 gal/h) for every 10,000 m
3
/h (5889 ft
3
/min). If the solids quantity

requires only 10% of the evaporation rate as a liquid bleed rate, then the dissolved solids in the water will be concentrated
by a factor of ten. Thus, 200 ppm of chloride would suddenly become 2000 ppm of chloride. This would be sufficient to
cause corrosion problems.
In most cases, fiberglass has been considered as a material of construction where abrasion is not particularly severe. In
other cases, carbon steel is used, particularly for coal handling or other applications in which abrasion is definitely
present.
Spray-drying applications typically require stainless steel. Either type 304 or 316 is used, depending on the particular
compound being collected. The use of stainless steel arises from the need for product purity. Because the slurry is usually
returned to the spray dryer, care must be taken to avoid any potential corrosion.
Chemical and Related Processing Plants
Chemical process and related industries experience a wide variety of potential corrosion problems. Many of the
compounds used have severe effects on many materials of construction. For air pollution control, the quantities of these
compounds can be greatly reduced, but the same corrosion problems may still be encountered. Obviously, it is important
to rely on the experience of the plant with its process equipment in selecting air pollution control equipment for exhaust
ventilation and process vents.
There are some specific differences, and the most important is the difference in operating pressure. Typically, the
ventilation systems of chemical reactors will be at atmospheric pressure. By comparison, the reactor itself may be at
several atmospheres of pressure. This is important because more economical materials of construction can often be
selected for the ventilation system, but they would not have the mechanical strength necessary to handle the pressure in
the reactor.
Because fiberglass can be used for atmospheric conditions, many of the clean-up systems used in chemical and process
plants are fabricated from fiberglass. The primary reason for using FRP is its low initial cost and good corrosion
resistance in a wide variety of services. The corrosion resistance of FRP is a function of both the resin content and the
specific resin used in the laminate.
Chloro-Alkali Plants. The production of chlorine results in severe corrosion problems. Quantities of chlorine in the
effluent gas are normally scrubbed using dilute caustic solutions. The most common material of construction is fiberglass.
Although fiberglass can be used in chlorine service, specific types of resin must be employed for this very difficult
application. Vinyl-ester resins are most commonly used. Numerous resins of the vinyl-ester type are available that can
handle chlorine and chlorides. In addition to using a high-performance resin, the inner glass reinforcement is usually
replaced with a synthetic veil to provide additional protection and to avoid any attack by hypochlorite or caustic on the

inner liner.
Fiberglass-reinforced plastic is typically used for the scrubbers handling chlorine removal, ductwork, fans, and stacks.
Even recycled pumps are manufactured of this material.
Where heat exchanges are used in the recycled solution, fiberglass is obviously not a practical material because of its low
heat transfer coefficient. For dilute hypochlorite solutions, such alloys as Hastelloy C-276 or Inconel 625 have been used.
Graphite can be used if the proper binder is selected. With the high heat transfer coefficients of plate heat exchangers,
constructions of Hastelloy C-276 can be economical.
Polyvinyl chloride or high temperature PVC (CPVC) is another material of construction that performs well in this service.
These materials are sometimes selected for small units or for ductwork construction.
Nitric Acid Plants. In nitric acid (HNO
3
) manufacture, stainless steel is the most common material of construction.
Concentrated HNO
3
will affect many of the nonmetallic materials of construction; therefore, FRP is not as common or as
easily accepted.
For many ventilation systems, either type 304 stainless steel or CPVC could be used. Fiberglass-reinforced plastic could
also be used when the acid is being neutralized. Relative costs are shown in Figure 3. Because the cost of stainless steel is
still relatively high compared to that of FRP, this alternative should be considered where very dilute acid concentrations
are involved. Where concentration and return to the process are involved, stainless steel remains the best solution.
In many cases, HNO
3
manufacture also produces oxides
of nitrogen. Nitric oxide (NO) and nitrogen dioxide (NO
2
)
would be handled by the same materials of construction.
Most commonly, these are removed from the air by using
scrubbing systems.The recycled solution becomes a dilute
HNO

3
solution. A special wet-phase catalyst has been
developed for use on this service. This material has
properties very similar to those of stainless steel.
In other HNO
3
facilities, thermal reduction has been used
to eliminate the residual oxides of nitrogen from the air.
Where thermal reduction is used, there is no wet surface.
However, the possibility of condensation remains should
the system shut down. Therefore, the holders in such units
are typically stainless steel. The catalyst itself is normally
a ceramic material with a vanadium oxide or similar
catalyst applied to the surface. These materials are
selected by the manufacturers and would be compatible
with stainless steel components selected for ductwork,
fans, and other auxiliaries.
Sulfuric Acid Service. Sulfuric acid mist is collected
by fiber bed mist eliminators. Such units employ a glass
mat held inside of a vessel operating at low velocities to
remove submicron mists.
Fiber bed unit shells for H
2
SO
4
are either type 316
stainless steel or alloy 20Cb3. The relative economics
suggest the use type 316 stainless steel, although it may
suffer a small amount of attack.
Alloy 20Cb3 can be used for most ranges of acid that

would be encountered in air pollution control systems. If
the solution is weak enough, type 316 stainless steel can
be used. Also, if the temperatures are low enough, FRP
should be considered because of its low initial cost. It is
best to obtain coupons of the materials and to conduct
some initial testing at dilute conditions before making a
final decision. The industry practice is to use more and
more FRP on these inorganic acid applications because of
low initial cost.
Sulfur Dioxide Service. Sulfur dioxide has similar
requirements even though the initial solution formed is
usually a neutralized salt; that is, SO
2
is normally
absorbed using an alkali solution, such as lime or caustic.
This solution is a sodium or calcium sulfite/sulfate
mixture. It can be handled at low temperatures in
fiberglass and at higher temperatures in type 316L
stainless steel.
Because most of the gas is removed in the air pollution control equipment, the downstream equipment can often handled
using liners rather than expensive alloys. This is particularly true for the fan because epoxy coatings can be applied to the
fan housing. The wheel itself is recommended in solid alloy construction because of high speeds involved. The
combination of an epoxy liner and a stainless steel wheel can cost as much as 25% less than a solid stainless steel fan.
Discharge stacks are often treated on the same basis. Where the stacks are large enough, a coating can be applied to a
steel stack. Of course, the first selection might be an FRP stack if the temperature is low enough because of its elimination

Fig. 3 Relative costs of scrubber materials
of maintenance. More information on materials of construction for the chemical-processing industry is available in the
article "Corrosion in the Chemical-Processing Industry" in this Volume.
The Fertilizer Industry. Several severe problems can occur in the manufacture of fertilizers. Trace quantities of

fluorides in phosphates result in the formation of HF and tetrafluoride in the gas. Although these can be scrubbed out, the
resulting solution is extremely corrosive to most metals and fiberglass.
The most common solution is the use of FRP, but with the substitution of synthetic veils for the inner glass lining. The
FRP resin itself is not affected by the HF, but the internal glass could be. A small pinhole leading to the glass would result
in a catastrophic attack. This is avoided by substituting a synthetic veil for the glass. Fiberglass is used throughout the
industry as a standard. Polypropylene, PVC, and similar thermoplastics are also used. Nitrates and urea products are
typically handled by using type 304 stainless steel. As noted above, concentrated HNO
3
could attack FRP-type materials.
Lime Kiln and Similar Kiln Operations. Lime kilns are found in several applications, including the pulp and the
paper industry. Lime and other kiln applications result in a hot gas that contains dust.
Most kilns use a pollution control system. When possible, a dry collection system is used, because it allows the material
to be collected in a form that can be returned directly to the kiln. Some products are simply too reactive for this technique,
or the temperature of the kiln is too high. Wet scrubbers are then used.
Most of the scrubbers on kilns are manufactured of carbon steel. The problem of corrosion resistance is usually minimal
because the solutions tend to be alkaline or at least neutral. The primary problem is usually abrasion resistance. The basic
collectors are manufactured of carbon steel, and high-wear areas are often made of stainless steel. Some units use heat-
treated stainless steel, which is hardened for the wear-resistant areas. Another technique is to install liner to protect areas
of greater wear. Fiberglass-reinforced plastic is typically not used in this application.
Pulp and Paper Industry. Most of the pollution control problems in the pulp and paper industry consist of either the
organic sulfur compounds produced from digesting the pulp or the chlorine-related oxidizing agents produced from
bleaching the pulp. The reduced sulfur compounds are generally handled in FRP construction. Temperature limitations
are not normally a factor, because most of these applications are at temperatures of 80 °C (175 °F) or less Chlorine or
chlorine dioxide applications can be handled by materials of construction similar to those discussed in the section
"Chloro-Alkali Plants." More information on materials of construction for the pulp and paper industry is available in the
article "Corrosion in the Pulp and Paper Industry" in this Volume.
References
1.

J.R. Crum, E.L. Hibner, and R.W. Ross, Jr., "Corrosion Resistance of High-Nickel Alloys in Simulated SO

2
-
Scrubber Environments," Huntington Alloys, Inc.
2.

F.G. Hodge, High Performance Alloys Make Wet Scrubbers Work, Chem. Eng. Prog.,
Vol 74 (No. 10),
1978, p 84-88
3.

R.W. Kirchner, Materials of Construction for Flue-Gas-Desulfurization Systems, Chem. Eng.,
19 Sept 1983,
p 81-86
4.

D.C Agarwal and F.G Hodge, "Material Selection Processes and Case Histories Associated wit
h the
Hazardous Industrial and Municipal Waste Treatment Industries," Cabot Corporation
5.

R.W. Kirchner, Corrosion of Pollution Control Equipment, Chem. Eng. Prog., Vol 71 (No. 3), 1975, p 58-63
6.

H.D. Rice, Jr. and R.A Burford, "Corrosion of Gas-Scrub
bing Equipment in Municipal Refuse Incinerators,"
Paper presented at the International Corrosion Forum, National Association of Corrosion Engineers, 19-
23
March 1973
Selected References
• G.L. Crow and H.R. Horsman, Corrosion in Lime/Limestone Slurry Scrubbers for Coal-

Fired Boiler
Flue Gases, Mater. Perform., July 1981, p 35-45
• T.G. Gleason, How to Avoid Scrubbers Corrosion, Chem. Eng. Prog., Vol 71 (No.3), 1975, p 43-47
• E.C Hoxie and G.W. Tuffnell, A Summary of INCO Corrosion Tests in Power Plant F
lue Gas
Scrubbing Processes, in Resolving Corrosion Problems in Air Pollution Control Equipment,
National
Association of Corrosion Engineers, 1976, p 65-71
• T.S. Lee and R.O. Lewis, Evaluation of Corrosion Behavior of Materials in a Model SO
2
Scrubber
System, Mater. Perform., May 1985, p 25-32
• T.S. Lee and B.S. Phull, "Use of a Model Limestone SO
2
Scrubber to Evaluate Slurry Chloride Level
Effects on Corrosion Behavior," Paper presented at the APCA/IGCI/NACE Symposium on Solving
Problems in Air Pollution Control Equipment, Orlando, FL, Dec 1984
• B.S. Phull and T.S. Lee, " The Effect of Fly Ash and Fluoride on Corrosion Behavior in a Model SO
2

Scrubber," Paper presented at the International Corrosion Engineers, 25-29 March 1985
• S.L. Sakol and R.A. Schwartz, Construction Materials for Wet Scrubbers, Chem. Eng. Prog.,
Vol 70
(No. 8), 1974, p 63-68

Corrosion Rate Conversion Guide

Introduction
CORROSION RATE is the corrosion effect on a metal (change or deterioration) per unit of time. The type of corrosion
rate used depends on the technical system and on the type of corrosion effect. Thus, corrosion rate may be expressed as an

increase in corrosion depth per unit of time (penetration rate, for example, mils/yr) or the mass of metal turned into
corrosion products per unit area of surface per unit of time (weight loss, for example, g/m
2
/d). The corrosion effect may
vary with time and may not be the same at all points of the corroding surface. Therefore, reports of corrosion rates should
be accompanied by information on the type, time dependency, and location of the corrosion effect.
Conversion of Corrosion Rates
Table 1 provides factors for converting among units commonly used for expressing corrosion rates. Table 2 is a
nomograph for conversion of corrosion rates.
Table 1 Relationships among some of the units commonly used for corrosion rates
d is metal density in grams per cubic centimeter (g/cm
3
)
Factor for conversion to Unit
mdd g/m
2
/d μm/yr

mm/yr mils/yr

in./yr
Milligrams per square decimeter per day (mdd)

1 0.1 36.5/d 0.0365/d

1.144/d

0.00144/d

Grams per square meter per day (g/m

2
/d 10 1 365/d 0.365/d 14.4/d 0.0144/d
Microns per year (μm/yr) 0.0274d

0.00274d

1 0.001 0.0394 0.0000394

Millimeters per year (mm/yr) 27.4d 2.74d 1000 1 39.4 0.0394
Mils per year (mils/yr) 0.696d 0.0696d 25.4 0.0254 1 0.001
Inches per year (in./yr) 696d 69.6d 25,400

25.4 1000 1
Source: G. Wranglén, An Introduction to Corrosion and Protection of Metals, Chapman and Hall, 1985, p. 238






Table 2 Nomograph for conversion of corrosion rates.
The example given is for type 304 stainless steel (density 7.87 g/cm
3
) and a corrosion rate of 30 mils/yr.


Glossary of Terms

o A
• absorption

• A process in which fluid molecules are taken up by a liquid or solid and distributed throughout
the body of that liquid or solid. Compare with adsorption .
• accelerated corrosion test
• Method designed to approximate, in a short time, the deteriorating effect under normal long-term
service conditions.
• acid
• A chemical substance that yields hydrogen ions (H
+
) when dissolved in water. Compare with base
.
• acid embrittlement
• A form of hydrogen embrittlement that may be induced in some metals by acid.
• acid rain
• Atmospheric precipitation with a pH below 5.6 to 5.7. Burning of fossil fuels for heat and power
is the major factor in the generation of oxides of nitrogen and sulfur, which are converted into
nitric and sulfuric acids washed down in the rain. See also atmospheric corrosion .
• acicular ferrite
• A highly substructured non-equiaxed ferrite formed upon continuous cooling by a mixed
diffusion and shear mode of transformation that begins at a temperature slightly higher than the
transformation temperature range for upper bainite. It is distinguished from bainite in that it has a
limited amount of carbon available; thus, there is only a small amount of carbide present.
• acrylic
• Resin polymerized from acrylic acid, methacrylic acid, esters of these acids, or acrylonitrile.
• activation
• The changing of a passive surface of a metal to a chemically active state. Contrast with
passivation .
• active
• The negative direction of electrode potential . Also used to described corrosion and its associated
potential range when an electrode potential is more negative than an adjacent depressed corrosion
rate (passive) range.

• active metal
• A metal ready to corrode, or being corroded.
• active potential
• The potential of a corroding material.
• activity
• A measure of the chemical potential of a substance, where chemical potential is not equal to
concentration, that allows mathematical relations equivalent to those for ideal systems to be used
to correlate changes in an experimentally measured quantity with changes in chemical potential.
• activity (ion)
• The ion concentration corrected for deviations from ideal behavior. Concentration multiplied by
activity coefficient.
• activity coefficient
• A characteristic of a quantity expressing the deviation of a solution from ideal thermodynamic
behavior; often used in connection with electrolytes.
• addition agent
• A substance added to a solution for the purpose of altering or controlling a process. Examples
include wetting agents in acid pickles, brighteners or antipitting agents in plating solutions, and
inhibitors.
• adsorption
• The surface retention of solid, liquid, or gas molecules, atoms, or ions by a solid or liquid.
Compare with absorption .
• aeration
• (1) Exposing to the action of air. (2) Causing air to bubble through. (3) Introducing air into a
solution by spraying, stirring, or a similar method. (4) Supplying or infusing with air, as in sand
or soil.
• aeration cell (oxygen cell)
• See differential aeration cell .
• age hardening
• Hardening by aging , usually after rapid cooling or cold working.
• aging

• A change in the properties of certain metals and alloys that occurs at ambient or moderately
elevated temperatures after hot working or a heat treatment (quench aging in ferrous alloys,
natural or artificial aging in ferrous and nonferrous alloys) or after a cold-working operation
(strain aging). The change in properties is often, but not always, due to a phase change
(precipitation), but never involves a change in chemical composition of the metal or alloy. See
also age hardening , artificial aging , natural aging , overaging , precipitation hardening ,
precipitation heat treatment , quench aging , and strain aging .
• alclad
• Composite wrought product comprised of an aluminum alloy core having on one or both surfaces
a metallurgically bonded aluminum or aluminum alloy coating that is anodic to the core and thus
electrochemically protects the core against corrosion.
• alkali metal
• A metal in group IA of the periodic system namely, lithium, sodium, potassium, rubidium,
cesium, and francium. They form strongly alkaline hydroxides, hence the name.
• alkaline
• (1) Having properties of an alkali. (2) Having a pH greater than 7.
• alkaline cleaner
• A material blended from alkali hydroxides and such alkaline salts as borates, carbonates,
phosphates, or silicates. The cleaning action may be enhanced by the addition of surface-active
agents and special solvents.
• alkyd
• Resin used in coatings. Reaction products of polyhydric alcohols and polybasic acids.
• alkylation
• (1) A chemical process in which an alkyl radical is introduced into an organic compound by
substitution or addition. (2) A refinery process for chemically combining isoparaffin with olefin
hydrocarbons.
• alligatoring
• (1) Pronounced wide cracking over the entire surface of a coating having the appearance of
alligator hide. (2) The longitudinal splitting of flat slabs in plane parallel to the rolled surface.
Also called fish-mouthing.

• alloy plating
• The codeposition of two or more metallic elements.
• alpha ferrite
• See ferrite .
• alpha iron
• The body-centered cubic form of pure iron, stable below 910 °C (1670 °F).
• alternate-immersion test
• A corrosion test in which the specimens are intermittently exposed to a liquid medium at definite
time intervals.
• aluminizing
• Forming of an aluminum or aluminum alloy coating on a metal by hot dipping, hot spraying, or
diffusion.
• amalgam
• An alloy of mercury with one or more other metals.
• ammeter
• An instrument for measuring the magnitude of electric current flow.
• amorphous solid
• A rigid material whose structure lacks crystalline periodicity; that is, the pattern of its constituent
atoms or molecules does not repeat periodically in three dimensions. See also metallic glass.
• amphoteric
• A term applied to oxides and hydroxides which can act basic toward strong acids and acidic
toward strong alkalis. Substances which can dissociate electrolytically to produce hydrogen or
hydroxyl ions according to conditions.
• anchorite
• A zinc-iron phosphate coating for ion and steel.
• anaerobic
• Free of air or uncombined oxygen.
• anion
• A negatively charged ion that migrates through the electrolyte toward the anode under the
influence of a potential gradient. See also cation and ion .

• annealing
• A generic term denoting a treatment, consisting of heating to and holding at a suitable
temperature, followed by cooling at a suitable rate, used primarily to soften metallic materials,
but also to simultaneously produce desired changes in other properties or in microstructure. The
purpose of such changes may be, but is not confined to, improvement of machinability,
facilitation of cold work, improvement of mechanical or electrical properties, and/or increase in
stability of dimensions. When the term is used by itself, full annealing is implied. When applied
only for the relief of stress, the process is properly called stress relieving or stress-relief
annealing.
• anode
• The electrode of an electrolyte cell at which oxidation occurs. Electrons flow away from the
anode in the external circuit. It is usually at the electrode that corrosion occurs and metal ions
enter solution. Contrast with cathode .
• anode corrosion
• The dissolution of a metal acting as an anode .
• anode corrosion efficiency
• The ratio of the actual corrosion (weight loss) of an anode to the theoretical corrosion (weight
loss) calculated by Faraday's law from the quantity of electricity that has passed.
• anode effect
• The effect produced by polarization of the anode in electrolysis. It is characterized by a sudden
increase in voltage and corresponding decrease in amperage due to the anode becoming virtually
separated from the electrolyte by a gas film.
• anode efficiency
• Current efficiency at the anode .
• anode film
• (1) The portion of solution in immediate contact with the anode , especially if the concentration
gradient is steep. (2) The outer layer of the anode itself.
• anode polarization
• See polarization .
• anodic cleaning

• Electrolytic cleaning in which the work is the anode. Also called reverse-current cleaning.
• anodic coating
• A film on a metal surface resulting from an electrolytic treatment at the anode .
• anodic inhibitor
• A chemical substance or mixture that prevents or reduces the rate of the anodic or oxidation
reaction. See also inhibitor .
• anodic polarization
• The change of the electrode potential in the noble (positive) direction due to current flow. See
also polarization .
• anodic protection
• (1) A technique to reduce the corrosion rate of a metal by polarizing it into its passive region,
where dissolution rates are low. (2) Imposing an external electrical potential to protect a metal
from corrosive attack. (Applicable only to metals that show active-passive behavior.) Contrast
with cathodic protection .
• anodic reaction
• Electrode reaction equivalent to a transfer of positive charge from the electronic to the ionic
conductor. An anodic reaction is an oxidation process. An example common in corrosion is:
Me Me
n+
+ ne
-
.
• anodizing
• Forming a conversion coating on a metal surface by anodic oxidation; most frequently applied to
aluminum.
• anolyte
• The electrolyte adjacent to the anode in an electrolytic cell .
• anti-fouling
• Intended to prevent fouling of underwater structures, such as the bottoms of ships.
• antipitting agent

• An addition agent for electroplating solutions to prevent the formation of pits or large pores in the
electrodeposit.
• aqueous
• Pertaining to water; an aqueous solution is made by using water as a solvent.
• artificial aging
• Aging above room temperature. See also aging . Compare with natural aging .
• atmospheric corrosion
• The gradual degradation or alteration of a material by contact with substances present in the
atmosphere, such as oxygen, carbon dioxide, water vapor, and sulfur and chlorine compounds.
• austenite
• A solid solution of one or more elements in face-centered cubic iron. Unless otherwise designated
(such as nickel austenite), the solute is generally assumed to be carbon.
• austenitizing
• Forming austenite by heating a ferrous alloy into the transformation range (partial austenitizing)
or above the transformation range (complete austenitizing). When used without qualification, the
term implies complete austenitizing.
• auxiliary anode
• In electroplating, a supplementary anode positioned so as to raise the current density on a certain
area of the cathode and thus obtain better distribution of plating.
• auxiliary electrode
• An electrode commonly used in polarization studies to pass current to or from a test electrode. It
is usually made from a noncorroding material.
• B
• backfill
• Material placed in a drilled hole to fill space around anodes, vent pipe, and buried components of
a cathodic protection system.
• bainite
• A metastable aggregate of ferrite and cementite resulting from the transformation of austenite at
temperatures below the pearlite range but above M
s

, the martensite start temperature. Bainite
formed in the upper part of the bainite transformation range has a feathery appearance; bainite
formed in the lower part of the range has an acicular appearance resembling that of tempered
martensite.
• banded structure
• A segregated structure consisting of alternating nearly parallel bands of different composition,
typically aligned in the direction of primary hot working.
• base
• A chemical substance that yields hydroxyl ions (OH
-
) when dissolved in water. Compare with
acid .
• base metal
• (1) The metal present in the largest proportion in an alloy; brass, for example, is a copper-base
alloy. (2) An active metal that readily oxidizes, or that dissolves to form ions. (3) The metal to be
brazed, cut, soldered, or welded. (4) After welding, that part of the metal which was not melted.
• beach marks
• Macroscopic progression marks on a fatigue fracture or stress-corrosion cracking surface that
indicate successive positions of the advancing crack front. The classic appearance is of irregular
elliptical or semielliptical rings, radiating outward from one or more origins. Beach marks (also
known as clamshell marks or arrest marks) are typically found on service fractures where the part
is loaded randomly, intermittently, or with periodic variations in mean stress or alternating stress.
See also striation .
• biaxial stress
• See principal stress (normal) .
• biological corrosion
• Deterioration of metals as a result of the metabolic activity of microorganisms.
• bipolar electrode
• An electrode in an electrolytic cell that is not mechanically connected to the power supply, but is
so placed in the electrolyte, between the anode and cathode , that the part nearer the anode

becomes cathodic and the part nearer the cathode becomes anodic. Also called intermediate
electrode.
• bituminous coating
• Coal tar or asphalt-base coating.
• black liquor
• The liquid material remaining from pulpwood cooking in the soda or sulfate papermaking
process.
• black oxide
• A black finish on a metal produced by immersing it in hot oxidizing salts or salt solutions.
• blister
• A raised area, often dome shaped, resulting from (1) loss of adhesion between a coating or
deposit and the base metal or (2) delamination under the pressure of expanding gas trapped in a
metal in a near-subsurface zone. Very small blisters may be called pinhead blisters or pepper
blisters.
• blow down
• (1) Injection of air or water under high pressure through a tube to the anode area for the purpose
of purging the annular space and possibly correcting high resistance caused by gas blocking. (2)
In connection with boilers or cooling towers, the process of discharging a significant portion of
the aqueous solution in order to remove accumulated salts, deposits, and other impurities.
• blue brittleness
• Brittleness exhibited by some steels after being heated to a temperature within the range of about
200 to 370 °C (400 to 700 °F), particularly if the steel is worked at the elevated temperature.
• blushing
• Whitening and loss of gloss of a usually organic coating caused by moisture. Also called
blooming.
• brackish water
• (1) Water having salinity values ranging from approximately 0.5 to 17 parts per thousand. (2)
Water having less salt than seawater, but undrinkable.
• breakdown potential
• The last noble potential where pitting or crevice corrosion , or both, will initiate and propagate.

• brightener
• An agent or combination of agents added to an electroplating bath to produce a smooth, lustrous
deposit.
• brine
• Seawater containing a higher concentration of dissolved salt than that of the ordinary ocean.
• brittle fracture
• Separation of a solid accompanied by little or no macroscopic plastic deformation. Typically,
brittle fracture occurs by rapid crack propagation with less expenditure of energy than for ductile
fracture .
• burning
• (1) Permanently damaging a metal or alloy by heating to cause either incipient melting or
intergranular oxidation. See also overheating . (2) In grinding, getting the work hot enough to
cause discoloration or to change the microstructure by tempering or hardening.
• C
• calcareous coating or deposit
• A layer consisting of a mixture of calcium carbonate and magnesium hydroxide deposited on
surfaces being cathodically protected because of the increased pH adjacent to the protected
surface.
• calomel electrode
• An electrode widely used as a reference electrode of known potential in electrometric
measurement of acidity and alkalinity, corrosion studies, voltammetry, and measurement of the
potentials of other electrodes. See also electrode potential , reference electrode , and saturated
calomel electrode .
• calorizing
• Imparting resistance to oxidation to an iron or steel surface by heating in aluminum powder at
800 to 1000 °C (1470 to 1830 °F).
• carbonitriding
• A case hardening process in which a suitable ferrous material is heated above the lower
transformation temperature in a gaseous atmosphere of such composition as to cause
simultaneous absorption of carbon and nitrogen by the surface and, by diffusion, create a

concentration gradient. The process is completed by cooling at a rate that produces the desired
properties in the workpiece.
• carburizing
• Absorption and diffusion of carbon into solid ferrous alloys by heating, to a temperature usually
above Ac
3
, in contact with a suitable carbonaceous material. A form of case hardening that
produces a carbon gradient extending inward from the surface, enabling the surface layer to be
hardened either by quenching directly from the carburizing temperature or by cooling to room
temperature, then reaustenitizing and quenching.
• case hardening
• A generic term covering several processes applicable to steel that change the chemical
composition of the surface layer by absorption of carbon, nitrogen, or a mixture of the two and,
by diffusion, create a concentration gradient. The outer portion, or case, is made substantially
harder than the inner portion, or core. The processes commonly used are carburizing and quench
hardening; cyaniding; nitriding; and carbonitriding. The use of the applicable specific process
name is preferred.
• CASS test
• See copper-accelerated salt-spray test .
• cathode
• The electrode of an electrolytic cell at which reduction is the principal reaction. (Electrons flow
toward the cathode in the external circuit.) Typical cathodic processes are cations taking up
electrons and being discharged, oxygen being reduced, and the reduction of an element or group
of elements from a higher to a lower valence state. Contrast with anode .
• cathode efficiency
• Current efficiency at the cathode .
• cathode film
• The portion of solution in immediate contact with the cathode during electrolysis .
• cathodic cleaning
• Electrolytic cleaning in which the work is the cathode .

• cathodic corrosion
• Corrosion resulting from a cathodic condition of a structure usually caused by the reaction of an
amphoteric metal with the alkaline products of electrolysis .
• cathodic disbondment
• The destruction of adhesion between a coating and its substrate by products of a cathodic reaction
.
• cathodic inhibitor
• A chemical substance or mixture that prevents or reduces the rate of the cathodic or reduction
reaction.
• cathodic pickling
• Electrolytic pickling in which the work is the cathode .
• cathodic polarization
• The change of the electrode potential in the active (negative) direction due to current flow. See
also polarization .
• cathodic protection
• (1) Reduction of corrosion rate by shifting the corrosion potential of the electrode toward a less
oxidizing potential by applying an external electromotive force . (2) Partial or complete
protection of a metal from corrosion by making it a cathode , using either a galvanic or an
impressed current. Contrast with anodic protection .
• cathodic reaction
• Electrode reaction equivalent to a transfer of negative charge from the electronic to the ionic
conductor. A cathodic reaction is a reduction process. An example common in corrosion is: Ox +
ne
-
Red.
• catholyte
• The electrolyte adjacent to the cathode of an electrolytic cell.
• cation
• A positively charged ion that migrates through the electrolyte toward the cathode under the
influence of a potential gradient. See also anion and ion .

• caustic
• (1) Burning or corrosive. (2) A hydroxide of a light metal, such as sodium hydroxide or
potassium hydroxide.
• caustic dip
• A strongly alkaline solution into which metal is immersed for etching, for neutralizing acid, or for
removing organic materials such as greases or paints.
• caustic embrittlement
• An obsolete historical term denoting a form of stress-corrosion cracking most frequently
encountered in carbon steels or iron-chromium-nickel alloys that are exposed to concentrated
hydroxide solutions at temperatures of 200 to 250 °C (400 to 480 °F).
• cavitation
• The formation and instantenous collapse of innumerable tiny voids or cavities within a liquid
subjected to rapid and intense pressure changes. Cavitation produced by ultrasonic radiation is
sometimes used to effect violent localized agitation. Cavitation caused by severe turbulent flow
often leads to cavitation damage .
• cavitation corrosion
• A process involving conjoint corrosion and cavitation .
• cavitation damage
• The degradation of a solid body resulting from its exposure to cavitation . This may include loss
of material, surface deformation, or changes in properties or appearance.
• cavitation-erosion
• Progressive loss of original material from a solid surface due to continuing exposure to cavitation
.
• cell
• Electrochemical system consisting of an anode and a cathode immersed in an electrolyte . The
anode and cathode may be separate metals or dissimilar areas on the same metal. The cell
includes the external circuit, which permits the flow of electrons from the anode toward the
cathode. See also electrochemical cell .
• cementite
• A compound of iron and carbon, known chemically as iron carbide and having the approximate

chemical formula Fe
3
C. It is characterized by an orthorhombic crystal structure. When it occurs
as a phase in steel, the chemical composition will be altered by the presence of manganese and
other carbide-forming elements.
• chalking
• The development of loose removable powder at the surface of an organic coating usually caused
by weathering.
• checking
• The development of slight breaks in a coating that do not penetrate to the underlying surface.
• checks
• Numerous, very fine cracks in a coating or at the surface of a metal part. Checks may appear
during processing or during service and are most often associated with thermal treatment or
thermal cycling. Also called check marks, checking , or heat checks.
• chelate
• (1) A molecular structure in which a heterocyclic ring can be formed by the unshared electrons of
neighboring atoms. (2) A coordination compound in which a heterocyclic ring is formed by a
metal bound to two atoms of the associated ligand. See also complexation .
• chelating agent
• (1) An organic compound in which atoms form more than one coordinate bond with metals in
solution. (2) A substance used in metal finishing to control or eliminate certain metallic ions
present in undesirable quantities.
• chelation
• A chemical process involving formation of a heterocyclic ring compound that contains at least
one metal cation or hydrogen ion in the ring.
• Chemical conversion coating
• A protective or decorative nonmetallic coating produced in situ by chemical reaction of a metal
with a chosen environment. It is often used to prepare the surface prior to the application of an
organic coating.
• chemical potential

• In a thermodynamic system of several constituents, the rate of change of the Gibbs function of the
system with respect to the change in the number of moles of a particular constituent.
• chemical vapor deposition
• A coating process, similar to gas carburizing and carbonitriding, whereby a reactant atmosphere
gas is fed into a processing chamber where it decomposes at the surface of the workpiece,
liberating one material for either absorption by, or accumulation on, the workpiece. A second
material is liberated in gas form and is removed from the processing chamber, along with excess
atmosphere gas.
• chemisorption
• The binding of an adsorbate to the surface of a solid by forces whose energy levels approximate
those of a chemical bond. Contrast with physisorption .
• chevron pattern
• A fractographic pattern of radial marks (shear ledges) that look like nested letters "V"; sometimes
called a herringbone pattern. Chevron patterns are typically found on brittle fracture surfaces in