Improving the corrosion performance of Cr–C amorphous coatings on steel substrate by modifying the steel surface preparation

Cr–C coating was electrodeposited on copper and steel substrates, using a trivalent chromium bath containing formic acid. Coatings produced had an amorphous cracked structure with a homogeneous granular morphology. The coated copper specimen showed passivation behaviour, but, the coated steel specimens revealed an active anodic behaviour. Evaluation of coatings produced on the steel substrate subjected to various surface preparations including mechanically polished, electropolished and anodically etched, showed a crack-free coating on the preanodically etched surface. Also, this coating had the lowest porosity, which provided the best protection and thus led to the lowest dissolution of the steel substrate.