CORROSIVE AND ELECTROCHEMICAL-BEHAVIOR OF DEPOSITS FROM CHROMIC-ACID ELECTROLYTES CONTAINING FORMIC-ACID

The high corrosion resistance of amorphous coatings deposited from chr omic acid electrolytes containing formic acid is shown to be caused by carbon incorporated into the coatings, rather than by their amorphous structure. The unusual shape of the voltammograms (no region of activ e dissolution is present) is attributed to inhibited chromium dissolut ion, a decreased hydrogen overvoltage, and the formation of a passivat ing film at the metal surface. The latter factor predominates and cont rols the corrosive and electrochemical behavior of chromium-carbon coa tings.