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开发一种环境友好的方法合成碳钠铝石转化膜以提高AZ31镁合金的耐蚀性。该膜由两步法制得:首先将AZ31合金浸泡在一直通CO2气体的Al2(SO4)3溶液中,获得前躯体膜;随后将该前躯体膜浸泡在溶有Al的Na2CO3溶液中以获得碳钠铝石膜。通过环境扫描电镜观察转化膜的表面形貌,并利用EDS能谱和X射线衍射分析其化学成分。采用电化学和浸泡实验来评价该转化膜对AZ31合金的防护作用。结果表明:膜的表面存在网状裂痕,其成分主要为碳钠铝石NaAlCO3(OH)2、Al(OH)3和Al5(OH)13(CO3)·5H2O。该膜能提高Mg基体的自腐蚀电位,并减少其腐蚀电流密度。浸泡实验后,除了局部小区域有个别点蚀坑外,膜基本保持完整;而基体却腐蚀严重。说明碳钠铝石转化膜能很好地保护镁合金。
An environmentally friendly method was developed for the synthesis of a dawsonite conversion coating to improve the corrosion resistance of AZ31 magnesium alloys. The film was prepared by a two-step process: the AZ31 alloy was first immersed in an Al2 (SO4) 3 solution that had been passed with CO2 gas to obtain a precursor membrane; then, the precursor membrane was soaked in a Na2CO3 solution with Al to obtain carbon Sodium aluminum stone film. The surface morphology of the conversion coating was observed by environmental scanning electron microscope, and its chemical composition was analyzed by EDS and X-ray diffraction. Electrochemical and immersion experiments were performed to evaluate the protective effect of the conversion coating on AZ31 alloy. The results show that there are reticular cracks on the surface of the membrane. The main components are NaAlCO3 (OH) 2, Al (OH) 3 and Al5 (OH) 13 (CO3) · 5H2O. The film can improve the self-corrosion potential of Mg matrix and reduce its corrosion current density. Immersion experiment, in addition to a small area of ?? individual pitting pits, the film remained intact; and the substrate was severely corroded. Description of the canitite conversion coating can well protect the magnesium alloy.