APPENDIX B 



GLOSSARY OF CORROSION TERMS 



Terms used in corrosion prevention and maintenance techniques are defined 

 telow. • 



Adsorption . The taking up of one substance at the surface of another is 

 termed adsorption. It is the tendency exhibited by all solids to condense 

 upon their surfaces a layer of any gas or solute with which such solids 

 are in contact. 



Aeration cell (oxygen cell ). An aeration cell is an electrolytic cell, 

 the e.m.f. of which is caused by a difference in air (oxygen) concentra- 

 tion at one electrode as compared with that at another electrode of the 

 same material. 



Aggressive carbon dioxide. Free carbon dioxide in excess of the amount 



necessary to prevent precipitation of calcium as calcium carbonate is 

 termed aggressive carbon dioxide. 



Amphoteric corrosion . Amphoteric materials are those materials that are 

 subject to attack from both acid and alkaline environments. Aluminum 

 and lead, commonly used in construction, are subject to amphoteric cor- 

 rosion in highly alkaline environments. Such corrosion is usually caused 

 by a chemical reaction resulting from a concentration of alkaline products 

 formed by the electrochemical process. The use of cathodic protection in 

 highly alkaline environments, therefore, intensifies the formation of 

 alkaline products. 



Anaerobic . Anaerobic means free of air or uncombined oxygen. 



Anion. A negatively charged ion of an electrolyte which migrates toward 

 the anode under the influence of a potential gradient . 



Anode . The electrode of an electrolytic cell at which oxidation occurs. 

 In corrosion processes, usually the electrode that has greater tendency 

 to go into solution. Typical anodic processes are anions giving up 

 electrons, metal atoms becoming ions in solution or forming an insoluble 

 compound of the metal, and the oxidation of an element or group of ele- 

 ments from a lower to a higher valence state. 



Anode corrosion efficiency . The ratio of the actual corrosion of an 

 anode to the theoretical corrosion calculated from the quantity of 

 electricity that has passed or discharged from the anode. 



Anodic polarization . That portion of the polarization of a cell that 

 occurs at the anode. 



Anolyte . The electrolyte of an electrolytic cell that is adjacent to 

 the anode . 



B-1 



