Development of High Performance Chromium-Free Passivation Agent Suitable for Coating of Aluminum Alloy and Optimization of Passivation Technology

An environmentally acceptable Cr-and P-free passivation agent SF-563 suitable for coating of Al wares was developed.The optimized passivation technology was established,and the properties of as-obtained passivation coating were evaluated.As the results,the optimized passivation parameters are suggested as bath concentration of 2%(mass fraction),pH value of 2.5～3.5,passivation time of 60～90 s,and passivation temperature of 10～35 ℃.Upon completion of passivation,the treated Al alloy surface does not need to be washed with water and can be directly dried at a maximum temperature of 120 ℃.Besides,the high-performance chemical conversion coating obtained under the optimized passivation parameters possesses excellent performance comparable to that of hexavalent Cr passivation coating,showing promising application in pre-treatment of Al alloy wares before coating.