David SCONYERS1, Cameron LONGO1, Mauricio QUIROZ-GUZMAN2, Douglas MORRISON2, Terrance BUSH2, Mark ARSENAULT2, Joshua MAURER1
1US Army DEVCOM AC, Watervliet, United States
2Trion Coatings, South Bend, United States
Hexavalent chromium electroplating has come under severe scrutiny, with increasingly strict regulations and plans for complete removal from operations within the US within the next 10 years. Hexavalent chromium poses large risks, as it is a known carcinogen and presents severe occupational and environmental hazards in its use. However, chromium coatings offer many benefits, including excellent wear and corrosion resistance, along with good hardness and adhesion properties. As such, an effective chromium plating alternative for hexavalent-based processes is sorely needed. Trivalent chromium systems represent a promising and safer alternative to existing technologies due to their decreased toxicity. However, fundamental challenges in addressing the thermodynamics and equilibria of chromium’s complex aqueous chemistry has made the successful development of new plating methodologies difficult. Present solutions incorporate a multitude of complexing agents that play unknown roles in stabilizing trivalent chromium itself or its reduced intermediates. An alternative approach is to use ionic liquids or ionic liquid/water mixed systems, which have a unique microstructure that could support and poise trivalent chromium for electrodeposition chemistries. Here, we explore the electrochemical profiles of imidazolium ionic liquid-based trivalent chromium electroplating systems, highlighting the strong dependence of the spectroscopic response and plating behavior on solution water content.