Electrochemical reduction of formic acid to diamond-like carbon films on stainless steel in aqueous solutions

Diamond-like carbon (DLC) films show attractive applications in surface modification of stainless steels (SS) owing to their high corrosion resistance and low friction coefficient. Electrodeposition is a cost-efficient method to prepare carbon films. DLC films were electrodeposited from formic acid solutions, however severe hydrogen evolution on stainless steel led to extremely low current efficiencies. Sodium formate was used to reduce the concentration of protons in the electrolyte and slightly improved the current efficiency. To further inhibit hydrogen evolution, dimethyl sulfoxide was added into the electrolyte as a proton acceptor. The current efficiency for carbon deposition increased more than 28 times, and the deposition rate reached as high as 1.6 μm h−1. The corrosion and wear resistance of DLC coated stainless steel were improved.