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采用阴极电泳技术在镁合金表面沉积防腐保护涂层,研究了KH460水溶性氨基硅烷预处理对阴极电泳涂层与基体镁合金的结合力及耐腐蚀性能的影响。采用SEM观察了镁合金表面硅烷膜层形貌,并通过极化曲线测试评价了膜层耐腐蚀性能。采用NMP测试及电化学交流阻抗分别评价了电泳涂层的抗溶胀能力及耐腐蚀性能。结果表明,硅烷膜层在镁合金表面非常薄呈透明状,且具有一定的防护性能。经硅烷预处理后可以大大提高镁合金阴极电泳涂层的结合力,NMP溶液浸泡170 h后涂层依然完整;无硅烷预处理试样则浸泡14 min之后,涂层完全脱落。此外,硅烷预处理也可极大地改善电泳涂层阻抗性能,涂层在5%NaC l溶液浸泡616 h后,低频阻抗值高达1×109Ω,比未预处理试样的阻抗高3个数量级,涂层仍然具有良好的阻挡腐蚀电解液渗透的能力,耐腐蚀性能优异。
Cathodic electrophoresis technique was used to deposit anticorrosive protective coating on the surface of magnesium alloy. The effect of KH460 water-soluble aminosilane pretreatment on the adhesion and corrosion resistance of cathodic electrodeposition coating and matrix magnesium alloy was studied. The morphology of the silane film on the surface of the magnesium alloy was observed by SEM, and the corrosion resistance of the film was evaluated by the polarization curve test. The anti-swelling ability and corrosion resistance of the electrophoretic coating were evaluated by NMP test and electrochemical impedance spectroscopy respectively. The results show that the silane film on the magnesium alloy surface is very thin and transparent, and has some protective properties. The pretreatment of silane can greatly improve the adhesion of magnesium alloy cathodic electrodeposition coating, the coating is still intact after 170 h of immersion in NMP solution, and completely disappeared after 14 min immersion of sample without silane. In addition, silane pretreatment can also greatly improve the performance of the electrophoretic coating impedance. After the coating is immersed in 5% NaCl solution for 616 h, the low frequency impedance is as high as 1 × 109Ω, which is 3 orders of magnitude higher than that of the non-pretreated sample. The coatings still have a good barrier against corrosive electrolyte penetration and excellent corrosion resistance.