ASTM_G_15_-_08.pdf

Designation:G15 08Standard Terminology Relating toCorrosion and Corrosion Testing1This standard is issued under the fixed designation G15;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1.Scope1.1 This terminology covers commonly used terms in thefield of corrosion.Related terms may be found in Terminolo-gies D16,D4538,G40,or other ASTM terminology standards.All terms defined by ASTM committees may be found in theASTM Dictionary of Engineering&Technology.2.Referenced Documents2.1 ASTM Standards:D16 Terminology for Paint,Related Coatings,Materials,and ApplicationsD4538 Terminology Relating to Protective Coating andLining Work for Power Generation FacilitiesG40 Terminology Relating to Wear and Erosion3.TerminologyAC impedanceSee electrochemical impedance.activenegative direction of electrode potential.(Also used todescribe corrosion and its associated potential range when anelectrode potential is more negative than an adjacent de-pressed corrosion rate passive range.)anionnegatively charged ion.anodeelectrode of an electrolytic cell at which oxidation isthe principal reaction.(Electrons flow away from the anodein the external circuit.It is usually the electrode wherecorrosion occurs and metal ions enter solution.)anode corrosion efficiencyratio of the actual corrosion(weight loss)of an anode to the theoretical corrosion(weightloss)calculated by Faradays law from the quantity ofelectricity that has passed.anodic inhibitorcorrosion inhibitor whose primary action isto slow the kinetics of the anodic reaction,producing apositive shift in corrosion potential.anodic polarizationchange of the electrode potential in thenoble(positive)direction due to current flow.(See polar-ization.)anodic protectiontechnique to reduce the corrosion rate of ametal by polarizing it into its passive region where dissolu-tion rates are low.anolyteelectrolyte adjacent to the anode of an electrolyticcell.auxiliary electrodeSee counter electrode.breakdown potentialleast noble potential where pitting orcrevice corrosion,or both,will initiate and propagate.cathodeelectrode of an electrolytic cell at which reduction isthe principal reaction.(Electrons flow toward the cathode inthe external circuit.)cathodic corrosioncorrosion of a metal when it is a cathode.(It usually happens to metals because of a rise in pH at thecathode or as a result of the formation of hydrides.)cathodic inhibitorcorrosion inhibitor whose primary actionis to slow the kinetics of the cathodic reaction,producing anegative shift in corrosion potential.cathodic polarizationchange of the electrode potential inthe active(negative)direction due to current flow.(Seepolarization.)cathodic protectiontechnique to reduce the corrosion rate ofa metal surface by making it the cathode of an electrochemi-cal cell.catholyteelectrolyte adjacent to the cathode of an electro-lytic cell.cationpositively charged ion.caustic crackingstress corrosion cracking of metals incaustic solutions.(See also stress-corrosion cracking.)caustic embrittlementSee caustic cracking.cavitationformation and rapid collapse within a liquid ofcavities or bubbles that contain vapor or gas or both.cavitation corrosionconjoint action of cavitation-erosionand corrosion.cavitation damagedegradation of a solid body resultingfrom its exposure to cavitation.(This may include loss ofmaterial,surface deformation,or changes in properties orappearance.)cavitation-erosionloss of material from a solid surface dueto mechanical action of continuing exposure to cavitation.1This terminology is under the jurisdiction of ASTM Committee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G01.02 onTerminology.Current edition approved May 1,2008.Published May 2008.Originallyapproved in 1971.Last previous edition approved in 2007 as G1507.DOI:10.1520/G0015-08.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.chemical conversion coatingprotective or decorative non-metallic coating produced in situ by chemical reaction of ametal with a chosen environment.(It is often used to preparethe surface prior to the application of an organic coating.)concentration cellelectrolytic cell,the emf of which iscaused by a difference in concentration of some componentin the electrolyte.(This difference leads to the formation ofdiscrete cathode and anode regions.)corrosionchemical or electrochemical reaction between amaterial,usually a metal,and its environment that producesa deterioration of the material and its properties.corrosion fatigueprocess in which a metal fractures prema-turely under conditions of simultaneous corrosion and re-peated cyclic loading