Coefficient of corrosion . A term used in applied cathodic protection. 

 The reciprocal of anode corrosion efficiency. 



Concentration cell . An electrolytic cell, the e.m.f. of which is the 

 result of a difference in concentration of the electrolyte or active 

 metal at the anode and the cathode. 



Concentration polarization . That portion of the polarization of an 

 electrolytic cell produced hy concentration changes resulting from pas- 

 sage of electric current through the electrolyte. 



Contact corrosion (crevice corrosion) . Corrosion of a metal at an area 

 where contact is made with a material usually nonmetallic. 



Corrosion . Destruction of a metal by chemical or electro-chemical 

 reaction with its environment. 



Corrosion fatigue . Reduction of fatigue durability by a corrosive 

 environment . 



Corrosion fatigue limit . The maximum repeated stress endured by a metal 

 without failure in a stated number of stress applications under defined 

 conditions of corrosion and stressing. 



Corrosion mitigation . The reduction of metal loss or damage through 

 use of protective methods and devices. 



Corrosion prevention . The halting or elimination of metal damage through 

 use of corrosion-resisting materials, protective methods, and protective 

 devices. 



Couple . A pair of dissimilar conductors in electrical contact. 



Couple action . (See galvanic corrosion. ) 



Cracking (of coating) . Breaks in a coating which extend through to the 

 underlying surface. Observation under a magnification of ten diameters 

 is recommended where there is difficulty in distinguishing between 

 cracking and checking. 



Crazing . Crazing is a network of checks and cracks appearing on a 

 surface. 



Critical humidity . The relative humidity above which the atmospheric 

 corrosion rate of a given metal increases sharply. 



Current density . The current per unit of cross-sectional area. In 

 cathodic protection work, the current density is usually expressed in 

 milliamperes per square foot . 



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