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通过在AA6063铝合金表面预沉积Ce~(3+),再浸涂双-[三-(乙氧基)硅丙基]四硫化物(BTST)的分步沉积工艺,制备了一种高耐蚀性的CeO_2/BTST复合转化膜。结果表明:单独CeO_2膜仅可使铝合金在3%NaCl溶液中的极化电阻提高一个数量级;但复合膜则可使之提高两个数量级,且点蚀电位上升近400 m V。CeO_2/BTST复合膜对铝合金亚稳态或稳态点蚀发展有强烈抑制作用,其噪声电阻达到10 MΩ·cm~2以上,在浸泡168 h内基本无亚稳态点蚀发生,而单独的CeO_2膜或BTST自组装膜的耐蚀性均有限,在3%NaCl溶液中浸泡168 h后铝合金表面即出现大量点蚀。由于CeO_2能优先吸附于第二相(AlFeSi)组织表面,抑制亚稳态点蚀生长;而硅氧烷与Al—O键结合能高,能有效提高Al基体的全面保护能力,得益于二者的协同作用,采用顺序沉积铈盐/硅氧烷所制备的复合保护层,能同时显著提升铝合金的全面腐蚀与局部腐蚀抗力。
A high resistance was obtained by a stepwise deposition process of pre-depositing Ce 3+ on the surface of AA6063 aluminum alloy and dipping with bis- [tri- (ethoxy) silyl] tetrasulfide (BTST) Erosive CeO 2 / BTST composite conversion coating. The results show that the CeO_2 film alone can only increase the polarization resistance of aluminum alloy in 3% NaCl solution by an order of magnitude, but the composite film can increase the polarization resistance by two orders of magnitude and the pitting potential increases by nearly 400 mV. CeO_2 / BTST composite film strongly inhibits the development of metastable or steady pitting corrosion of aluminum alloy, and the noise resistance reaches more than 10 MΩ · cm ~ 2, and almost no metastable pitting occurs within 168 h of immersion CeO 2 film or BTST self-assembled film has a limited corrosion resistance. After soaking in 3% NaCl solution for 168 h, a large amount of pitting corrosion occurs on the surface of the aluminum alloy. Because CeO 2 can preferentially adsorb on the surface of the second phase (AlFeSi), metastable pitting growth can be inhibited. Siloxane has a high binding energy with Al-O bond and can effectively improve the overall protection ability of Al matrix. The synergistic effect of using a sequential deposition of a composite protective layer of cerium salt / siloxane can significantly improve the overall corrosion resistance and the local corrosion resistance of the aluminum alloy.