Calomel electrode . A half-cell consisting of mercury, a paste of mercury 

 and calomel (mercurous chloride), and a standard solution of potassium 

 chloride saturated with calomel. It is used as a standard electrode in 

 potential difference measurements. 



Cathode . The electrode of an electrolytic cell at which reduction occurs. 

 In corrosion processes, usually the area that is not attacked. Typical 

 cathodic processes are cations taking up electrons and being discharged, 

 oxygen being reduced, and the reduction of an element or group of elements 

 from a higher to a lower valence state. 



Cathodic corrosion . Corrosion resulting from a cathodic condition of a 

 structure, usually caused by the reaction of alkaline products of elec- 

 trolysis with an amphoteric metal. 



Cathodic polarization . That portion of the polarization of an electroly- 

 tic cell which occurs at the cathode. 



Cathodic protection . Reduction or prevention of corrosion of a metal 

 surface by making it cathodic to the electrolyte, for example, by use of 

 sacrificial anodes « or impressed electrical currents. 



Catholyte . The electrolyte of an electrolytic cell adjacent to the 

 cathode. 



Cation . A positively charged ion of an electrolyte which migrates toward 

 the cathode under the influence of a potential gradient. 



Caustic embrittlement . Embrittlement of a metal resulting from contact 

 with an alkaline solution. 



Cavitation erosion . Damage of a metal associated with the formation and 

 collapse of cavities in the liquid at a solid-liquid interface. 



Chalking . The development of loose removable powder at, or just beneath, 

 a coating surface. 



Checking . The development of slight breaks in a coating that do not 

 penetrate to the underlying surface. Checking may be described as visible 

 (as seen by the naked eye) or as microscopic (as seen under the magnifica- 

 tion of ten diameters). 



Chemical conversion coating . A protective or decorative coating produced 

 in situ by chemical reaction of a metal with a chosen environment. 



Coating resistance . The electrical resistance of a coating to the flow 

 of current. Unit of measurement is ohms for one square foot of coating. 

 Typical values range from less than 1,000 ohms to more than 1,000,000 

 ohms for one square foot. 



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