Glossary
Cor·rode, v.t. to eat into or wear away gradually, as by rusting or by the action of chemicals.
WEBSTER’S NEW WORLD
DICTIONARY
Alteration The change or modification of a material through interaction with its environment, generally by the formation of a new phase. This reaction need not be deleterious.
Atmospheric Corrosion The degradation of materials by natural atmospheric environments. Atmospheric corrosion is a term often used by the metallurgist, whereas an equivalent term used by ceramists is weathering.
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Biodurability The ability of a ceramic to withstand the action of a biological environment.
Condensation Corrosion Equivalent to dew point corrosion.
Corrosion The chemical interaction of a ceramic with its environment, generally producing a deleterious effect. This chemical reaction can, in some cases, be put to beneficial use.
Dealkalization The corrosion of a ceramic through the selective solution of the alkalies into the corroding medium. Generally used to describe the removal of alkalies from glasses.
Degradation A general decrease or lowering of the quality of a ceramic; often through corrosive action.
Dewpoint Corrosion The deterioration of a solid ceramic material caused by the condensation of a corrosive liquid from a saturated gas when the temperature is lowered below the point (the dew point) where the liquid will condense. A form of atmospheric corrosion and equivalent to condensation corrosion.
Dissolution Corrosion The corrosion of a ceramic through the solution of its various components into the corroding medium
(generally a liquid).
Dissolution: Congruent, direct, or homogeneous When the total ceramic chemistry dissolves simultaneously into the environment.
Dissolution: Incongruent, Indirect, or Heterogeneous When the ceramic dissolves in such a way as to leave behind a material chemically different than the original ceramic as an interface between the ceramic and the corroding medium. These terms generally imply that the dissolution is selective.
Dissolution: Selective The corrosion of a ceramic through the selective solution of one or more (but not all) species into the corroding medium.
Dissolution: Anisotropic When the ceramic material dissolves
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at different rates parallel to different crystallographic or geometric directions.
Dissolution: Isotropic When the ceramic material dissolves at the same rate for all crystallographic or geometric directions.
Durability The ability of a ceramic to withstand the action of its environment.
Electrochemical Corrosion The corrosion that takes place when the reaction occurring involves electronic charge transfer. Generally this type occurs when ceramics are in contact with aqueous media, but may also occur in other media.
Galvanic Corrosion The corrosion that takes place when two chemically dissimilar ceramics are in contact with one another, both of which are in contact with the same electrolyte. Reaction occurs only when current flows in an external circuit. A type of electrochemical corrosion.
Hot corrosion Normally used to designate high temperature oxidation of ceramics in contact with molten salt deposits. This definition should probably not be used, since the term Hot Corrosion is nonspecific and could apply to any type of corrosion at an elevated temperature.
Intergranular or Grain Boundary Corrosion The corrosion through any mechanism that takes place preferentially along grain boundaries or between grains.
Leaching To remove through dissolution a portion of a ceramic material.
Leaching: Selective Removes one species in preference to another. The use of the word selective in this case is superfluous.
Oxidation Embrittlement The embrittlement of a composite caused by the oxidation of the interface between the reinforcement material and the matrix resulting in a strong bond between the two.
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Pesting The formation of a powder-like deposit on the exposed surface of metallic silicides (i.e., MoSi2) during oxidation.
Photoelectrochemical Corrosion Electrochemical corrosion that takes place when the charge transfer involves the positive holes formed by photon illumination. Also called photo-dissolution.
Stress Corrosion Corrosion by any mechanism that is enhanced by the presence of either a residual or applied stress.
Thermo-Oxidative Stability The resistance to oxidation at elevated temperatures. Generally used in the discussion of composite materials.
Weathering This term describes the atmospheric effects upon materials of the construction industry, mostly structural clay products, sandstone, limestone, marble, and glass; and is essentially the attack by water vapor, CO2, and SO2.
Copyright © 2004 by Marcel Dekker, Inc.