New Corrosion Inhibiting Cleaning System for Aluminum Alloys

Precoat surface cleaning of aluminum alloys is critical for removing common surface contaminants such as loose metal oxides, oils, and dirt that can impede wetting and adhesion of subsequently applied coatings. Many caustic cleaning processes cause matrix dealloying/redeposition of copper, which often results in copper on the aluminum alloy surface and localized corrosion initiation. A new cleaning process is proposed that effectively removes the surface contaminants and poorly adhered oxides while minimizing the corrosion-inducing redeposition of copper smut. The objective of the Phase I program is to identify candidate metal pretreatment systems which meet the goals of low toxicity, simple application, effective surface cleaning, passivation and copper-redeposition prevention for enhancing corrosion inhibition. A novel combination of surface-active compounds, inhibitors, and anti metal redeposition agents will be used to formulate the new aqueous-based cleaning systems. These pretreatment systems and suitable controls will be tested on common aircraft aluminum alloys for cleaning efficiency, inherent corrosion inhibition by potentiodynamic electrochemical analysis, compatibility with conversion coating application and paint adhesion. The costs, hazards, and environmental fate of effluents produced by the new cleaning processes will be estimated and used in the system design.