Influence of Additives on Aluminum (Al) Plating from Ionic Liquids

Abstract

Aluminum (Al) plating from ionic liquids has attracted both scientific and technological interest because it provides an eco-friendly, and drop-in replacement of cadmium as a corrosion protection coating. Considerable effort has been made to advance this ionic liquid-based Al plating process as a competitive commercial aluminum deposition technology. With the aim of the industrialization of the Al plating process, the use of additive-free electrolyte is preferred from ionic liquid plating bath durability. However, like conventional plating from aqueous solution, certain additives are required for smooth and high quality aluminum coatings from ionic liquids. Theoretically, these additives act as leveling or brightening agents to improve the quality of deposits but often at the cost of coating purity, and coating properties such as corrosion resistance. Therefore, a better scientific understanding of different additives on Al plating from ionic liquids from both Al plating process and Al coating performance would be beneficial to advance this commercially viable Al plating process from ionic liquids. In this work, commercially available ionic liquids, composed of both [Emim]Cl/AlCl3 and [Bmim]Cl/AlCl3 systems with different proprietary additives from suppliers were employed for the influence of additives on Al plating on both Cu and steel substrates. The resultant surface morphologies and adhesion and corrosion resistance of the Al coatings were evaluated, and further characterized by FIB/SEM/EDXS, demonstrating that all proprietary additives serve as a highly effective brightener, producing highly uniform and smooth Al deposits, but could lead to different Al coating performance.