Microstructure and corrosion resistance of hot-dip galvanized Zn-Ni-Al alloy coatings

Abstract

为探索不同成分的Zn-Ni-Al合金热浸镀件组织和耐腐蚀性能关系,了解微量铝对不同镀层组织、厚度和耐腐蚀性的综合影响规律,设计了4组Zn-0.10%Ni-x Al(x=0,0.08,0.12,0.15 wt.%)熔池合金对Q235钢进行热镀锌,利用光学显微镜、扫描电镜及能谱分析等技术对4种镀件镀层微观组织和合金成分进行观察和分析,并通过精密型盐雾试验机对其腐蚀速率进行测定和比较。实验结果表明,当锌液成分中含有0.08~0.15 wt.%Al时,镀层表面光亮美观,生成由δ(Fe Zn9)过渡层和η(Zn)锌层组成的致密镀层组织。Al含量在0.00~0.08 wt.%时,过渡层厚度呈现快速增大规律,Al含量在0.08~0.12 wt.%时,过渡层厚度出现减小趋势,而Al含量在0.12~0.15 wt.%时,过渡层厚度缓慢上升,而η(Zn)锌层厚度则表现为与过渡层厚度相反的变化规律。过渡层厚度越大,镀件的腐蚀速率越小,厚而致密的δ(Fe Zn9)过渡层对钢材的防护更有效。 Micro structure and corrosion resistance of the hot-dip galvanized Zn-Ni-Al alloy coatings have been studied to determine the optimal aluminum content and thus achieve hot-dip galvanized products with comprehensive performance. Four groups of molten pool alloys of Zn-0. 10% Ni-Al( x = 0,0. 08,0. 12,0. 15 wt. %) have been formulated. The Micro structure and phase identification of hot-dip galvanized alloy coating have been characterized by optical microscope,scanning electron microscope with energy dispersal spectroscopy. The corrosion rate has beeninvestigated by salt spray test. The results show that the bright hot-dip galvanized coating consists ofδ( Fe Zn9) transition layer and η( zinc) layer when 0. 08 - 0. 15 wt. % of aluminum has been added to the zinc-nickel bath. The hot-dip Zn-Ni-Al alloy coatings show not only compact Micro structure,but also good anti-corrosion properties. The average thickness of the δ( Fe Zn9) transition layer increases as Al varies from 0. 00 to 0. 08 wt. % at first,then decreases as Al increases from 0. 08 to0. 12 wt. %,and slightly increases as Al varies from 0. 12 to 0. 15 wt. % at last. The variation of η( zinc) layer thickness is contrary to that of δ( Fe Zn9) transition layer. The corrosion rate becomes smaller as the δ( Fe Zn9) transition layer become thicker. The improved corrosion resistance should be attributed to the increased thickness of δ( Fe Zn9) transition layer.国家自然科学青年科学基金资助项目(51601042); 有色金属及材料加工新技术教育部重点实验室开放基金资助项目(GXKFJ09-18); 广西高校科学技术研究资助项目(YB2014108); 广西民族大学教改资助项目(2014XJZZ14); 自治区级大学生创新创业训练计划资助项目(201510608153); 国家级大学生创新创业训练计划资助项目(201510608028

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