Plasma Pre-Treatment as a Superior Alternative to Conventional Electrochemical Etching of Steel for Aluminum Electrodeposition

Aluminum electrodeposition on steel typically requires electrochemical etching as the surface pre-treatment to achieve a crevice-free interface between deposited aluminum and steel substrate. However, electrochemical etching results in the dissolution of iron and other elements of the substrate, leading to the contamination of the chloroaluminate electrolyte. This results in the deterioration of the electrolyte bath and the subsequent development of an impure coating. These drawbacks can be solved by the proposed plasma treatment of the steel substrate prior to electrodeposition. This study explores the possibility of utilizing plasma treatment as a surface pre-treatment method for aluminum electrodeposition on steel. The effect of plasma pre-treatment on coating morphology, topography, crystal orientation, micro-hardness, and corrosion resistance (potentiodynamic polarization and electrochemical impedance spectroscopy test) was discussed and compared with that of the electrochemically etched sample. Plasma pre-treatment has resulted in a finer, denser, and smoother pristine aluminum coating, leading to a 32.4% increase in micro-hardness and 65.3% reduction in corrosion current over the electrochemically etched sample. The ability to electrodeposit pure aluminum without deteriorating the electrolyte, along with these enhanced performances, establishes plasma pre-treatment as the superior alternative to electrochemical etching.