Electrodeposition of chromium from Cr (III) electrolytes in the presence of formic acid

Chromium coatings deposited from sulphate, chloride and perchlorate electrolytes based on the Cr(H₂O)₄(HCOO)]²⁺ complex ion were investigated. The current efficiency reached 30% in the case of chloride electrolyte for various current densities in the range 4–10 A dm^-2 depending on pH. Such a large current efficiency is due to the catalytic effect of the chloride ions on the electroreduction of the chromium complex to metallic chromium. Deposition of chromium from sulphate electrolyte took place with a current efficiency of 16% which rose for higher pH and lower current densities. Semi-bright and bright coatings with thickness of approximately 10m of good adhesion to a copper electrode were deposited from chloride and sulphate electrolytes.