6061铝合金钛锆铈化学转化成膜过程及膜层的耐蚀性能

为进一步改善6061铝合金表面无铬化学转化膜的综合性能,以H2TiF6和H2ZrF6为主成膜剂,铈盐、偏磷酸盐等辅助成膜剂,制备了具有较高耐蚀性能的Ti-Zr-Ce化学转化膜。通过扫描电镜及能谱仪分析转化膜表面形貌及元素构成,并采用电子探针显微分析仪观察不同成膜阶段的铝合金微区结构的变化规律,研究了6061铝合金表面Ti-Zr-Ce化学转化成膜过程及膜层耐蚀性能。结果表明:膜层主要含有Al、O、Ti、P元素,还含有少量F、Zr元素,推测主要成分为TiO2,ZrO2,Al2O3及少量磷化物;极化曲线和交流阻抗测试表明Ti-Zr-Ce化学转化膜具有较好的耐蚀性能,反应时间为150s时制备的Ti-Zr-Ce转化膜试样的腐蚀电位为-0.577V,腐蚀电流密度较低,为0.115μA/cm^2.

Formation Process of Ti/Zr/Ce Chemical Conversion Coating on 6061 Aluminum Alloy and Its Corrosion Resistance

In order to further improve the comprehensive performance of the chromium-free chemical conversion coating of 6061 aluminum alloy, a chemical conversion coating with high corrosion resistance was obtained on the surface of the aluminum alloy with H2TiF6 and H2ZrF6 as the main coating formers and cerium salt and metaphosphate as auxiliaries. The surface morphology and elemental composition of the conversion coating were observed by SEM and EDS. The variation of micro-area structure of aluminum alloy at different coating formation stages was studied by EPMA. Results showed that the coating was mainly composed of Al, O, Ti, and P elements, and also contained a small amount of F and Zr. It was presumed that the main components were TiO2, ZrO2, Al2O3 and a small amount of phosphate. The Tafel curves and AC impedance tests showed that the chemical conversion coating had the better corrosion resistance. When the reaction time was 150 s, the corrosion potential of the chemical conversion coating was-0.577 V, and the corrosion current significantly decreased to 0.115μA/cm^2.