ASTM G15-02

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: G 15 – 02
Standard Terminology Relating to
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Corrosion and Corrosion Testing
This standard is issued under the fixed designation G 15; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
AC impedance—See electrochemical impedance. cathodic polarization—the change of the electrode potential
active—the negative direction of electrode potential. (Also in the active (negative) direction due to current flow. (See
used to describe corrosion and its associated potential range polarization.)
when an electrode potential is more negative than an cathodic protection—a technique to reduce the corrosion rate
adjacent depressed corrosion rate [passive] range.) of a metal surface by making it the cathode of an electro-
anion—a negatively charged ion. chemical cell.
anode—the electrode of an electrolytic cell at which oxidation catholyte—the electrolyte adjacent to the cathode of an
is the principal reaction. (Electrons flow away from the electrolytic cell.
anode in the external circuit. It is usually the electrode where cation—a positively charged ion.
corrosion occurs and metal ions enter solution.) caustic cracking—stress corrosion cracking of metals in
anode corrosion efficiency—the ratio of the actual corrosion caustic solutions. (See also stress corrosion cracking.)
(weight loss) of an anode to the theoretical corrosion (weight caustic embrittlement— See caustic cracking.
loss) calculated by Faraday’s law from the quantity of cavitation—the formation and rapid collapse within a liquid of
electricity that has passed. cavities or bubbles that contain vapor or gas or both.
anodic inhibitor—a corrosion inhibitor whose primary action cavitation corrosion—the conjoint action of cavitation-
is to slow the kinetics of the anodic reaction, producing a erosion and corrosion.
positive shift in corrosion potential. cavitation damage—the degradation of a solid body resulting
anodic polarization—the change of the electrode potential in from its exposure to cavitation. (This may include loss of
the noble (positive) direction due to current flow. (See material, surface deformation, or changes in properties or
polarization.) appearance.)
anodic protection—a technique to reduce the corrosion rate of cavitation-erosion—loss of material from a solid surface due
a metal by polarizing it into its passive region where to mechanical action of continuing exposure to cavitation.
dissolution rates are low. chemical conversion coating—a protective or decorative
anolyte—the electrolyte adjacent to the anode of an electro- nonmetallic coating produced in situ by chemical reaction of
lytic cell. a metal with a chosen environment. (It is often used to
auxiliary electrode—See counter electrode. prepare the surface prior to the application of an organic
breakdown potential—the least noble potential where pitting coating.)
or crevice corrosion, or both, will initiate and propagate. concentration cell—an electrolytic cell, the emf of which is
cathode—the electrode of an electrolytic cell at which reduc- caused by a difference in concentration of some component
tion is the principal reaction. (Electrons flow toward the in the electrolyte. (This difference leads to the formation of
cathode in the external circuit.) discrete cathode and anode regions.)
cathodic corrosion—corrosion of a metal when it is a cathode. corrosion—the chemical or electrochemical reaction between
(It usually happens to metals because of a rise in pH at the a material, usually a metal, and its environment that pro-
cathode or as a result of the formation of hydrides.) duces a deterioration of the material and its properties.
cathodic inhibitor—a corrosion inhibitor whose primary ac- corrosion fatigue—the process in which a metal fractures
tion is to slow the kinetics of the cathodic reaction, produc- prematurely under conditions of simultaneous corrosion and
ing a negative shift in corrosion potential. repeated cyclic loading at lower stress levels or fewer cycles
than would be required in the absence of the corrosive
environment.
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This terminology is under the jurisdiction of ASTM Committee G01 on
corrosion fatigue strength—the maximum repeated stress
Corrosion of Metals and are the direct responsibility of Subcommittee G01.02 on
that can be endured by a metal without failure under definite
Terminology.
Current edition approved June 10, 2002. Published July 2002. Originally
published as G 15 – 71. Last previous edition G 15 – 99b.
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