Investigation of the post-treatment process for improving corrosion behaviors and adhesion strength of plasma electrolytic oxidation (PEO) coatings on pure copper

The post-treatment processes of plasma electrolytic oxidation (PEO) coatings for corrosion behaviors and adhesion strength are investigated by surface analysis and electrochemical measurements. When the PEO coating is treated with high-temperature oxidation (HTO), silane coupling agent (SCA) mixed with benzotriazole (BTA) exhibits the optimal corrosion behaviors and adhesion strength, the icorr decreases to 0.65 ± 0.35 μA/cm2, ip decreases to 4.37 ± 0.42 μA/cm2, the Epit increases to 369.6 ± 0.4 mVSCE and the bonding strength increases to 14.2 MPa. That was mainly attributed to the corrosive medium with a longer diffusion path to the interface. Moreover, only the HTO treatment at 150 °C showed superior properties for long-time service, the icorr was 2.00 ± 0.17 μA/cm2, ip was 12.30 ± 0.09 μA/cm2, the Epit was −4.7 ± 0.2 mVSCE and the bonding strength was 10.0 MPa. That was ascribed to both the outer hydroxide and the inner oxide depicted the higher compactness.