Substrate Interaction Effects on the Structure of Chromium Electrodeposits

Abstract

Chrome-plating solutions dissolve copper, nickel, and steel substrates. In trivalent chromium solutions containing 40 ml/liter formic acid, the ions of the substrate metals codeposit to form alloy layers. When the formic-acid content was lower, no alloy layers developed. The alloy layers are initially mostly amorphous and then become crystalline regardless of current density. The chromium deposits which formed on the alloy layers were crystalline when the current density was low and amorphous when it was high. The internal stress in the alloy layers is higher than in plain chromium deposits.

Fundamental Considerations

“…Despite being cathodic, the substrate surface may dissolve in the plating solution and then redeposit with the plated metal as an alloy. Such is the case in some trivalent chromium plating solutions [46]. Etched substrate surfaces have been observed [47] to cause twins to form in the deposit.…”