Abstract
Cathodic corrosion in chromium plating baths was observed for several metals such as iron and copper and also on the surface of bright or non-bright nickel plating.
The test solutions were
(a) Aqueous solution of single chromic acid
(b) Two sorts of aqueous solutions containing each one of sulfuric and fluosilicic acids.
The results obtained were as follows:
(1) The potential region for cathodic corrosion in chromium plating baths corresponded with that for reduction of Cr6+→Cr3+ in chromium electrode reaction.
(2) The corrosion velocities of substrate metals were increased with the increase in concentrations of catalytic anions to be added.
(3) Bright nickel plating was more corroded than other metals in the bath containing sulfuric acid. On the other hand, both of iron and bright nickel plating were remarkably corroded in the bath containing fluosilicic acid.
(4) When the pulsation of current wave form of power source for rectified current for the plating was more rippled, the cathodic corrosion was more promoted.
