Influence of the Current Regime during Electrodeposition in a Cr(III)-Containing Fe-Cr-Ni Electrolyte on the Near-Surface pH, Alloy Composition, and Microcrack Behavior

This study shows the electrodeposition of Fe-Cr-Ni alloys using the advantages of a stepped direct-current deposition in a Cr(III)-containing electrolyte, and its influence on the pH value. The resulting coatings are uniform and free of microcracks, with a Cr content around 30% and thicknesses above 10 mu m. The influence of the current mode (direct current, stepped direct current, pulsed current) on pH development is investigated and correlated with the arising microstructure and alloy composition. Considering the current flow, it can be stated that pauses interrupt high overvoltage and restrain the pH increase at the cathode. The associated formation of chromium hydrides and their deposition onto the chromium layer, leading to cracking, is thus reduced. In this work, direct evidence for this theory and a suggestion for near-surface pH measurement during electrodeposition are presented.