Passivation of aerospace stainless parts with citric acid solutions

This edited version of the paper that won the Garland Award at the 2002 Aerospace/Airline Plating & Metal Finishing Forum describes the results of an evaluation of citric acid solutions used to passivate stainless steel alloys for aerospace applications. The evaluation includes sample preparation of stainless steel for conducting passivation tests, design of experiment studies to-determine optimum operating range for nitric and citric acid solutions, and comparison of AMS-QQ-P-35 nitric acid passivation solutions with citric acid solutions. The study supports the effectiveness of citric acid to passivate stainless steel, and the potential to have citric acid replace nitric acid passivation solutions that are currently being used in the aerospace industry.