热镀锌铝镁镀层的切边保护性能和耐腐蚀机理

发布时间：2018-09-13 05:50

【摘要】：采用SEM观察了成分不同热镀锌合金镀层的微观结构和镀层腐蚀后的表面形貌,用电化学和循环腐蚀试验分析镀层钢板的腐蚀行为和耐蚀性能,并用XRD分析镀层表面腐蚀产物的相组成。结果表明:热镀锌铝镁镀层中Al、Mg及Zn2Mg相的存在可以使镀层表面形成稳定的化合物,降低电化学试验时镀层的电流密度和溶解速度;镀层中的共晶相可以使Mg元素在镀层中均匀分布,从而抑制阴极反应;镀层腐蚀后形成的Zn5(OH)8Cl2·H2O和Zn6Al2(OH)16CO3·4H2O是不溶性的胶状腐蚀产物,可以有效隔断镀层与外界物质间的电子传输。腐蚀初期,Zn2Mg优先溶解,为腐蚀产物提供足够的Mg元素,部分Mg元素进入Zn的腐蚀产物中,形成Zn5(OH)8Cl2·H2O和Zn4CO3(OH)6·H2O。而Al3+和Mg2+的存在可以降低镀层中Zn4CO3(OH)6·H2O脱水形成无保护作用Zn O的趋势,增加Zn5(OH)8Cl2·H2O和Zn6Al2(OH)16CO3·4H2O等腐蚀产物的量,且Zn5(OH)8Cl2·H2O和Zn4CO3(OH)6·H2O填充于腐蚀缝隙中可以进一步阻止腐蚀的发生,使得镀层表面获得更低的电位,因而对阳极的分层扩散驱动力变小,降低切边部位在长期腐蚀中的溶解情况,提高镀层的耐蚀性能和切边保护性能。
[Abstract]:The microstructure and surface morphology of different hot-dip galvanized alloy coatings with different composition were observed by SEM. The corrosion behavior and corrosion resistance of the coatings were analyzed by electrochemical and cyclic corrosion tests. The phase composition of corrosion products was analyzed by XRD. The results show that the existence of Al,Mg and Zn2Mg phase in hot-dip galvanized aluminum-magnesium coating can result in the formation of stable compounds on the surface of the coating and decrease the current density and dissolution rate of the coating during the electrochemical test. The eutectic phase in the coating can make the Mg element distribute uniformly in the coating, thus restrain the cathodic reaction, and the Zn5 (OH) 8Cl2 H2O and Zn6Al2 (OH) 16CO3 4H2O formed after the coating corrosion are insoluble colloidal corrosion products, which can effectively separate the electron transport between the coating and the external material. In the early stage of corrosion, Zn _ 2Mg dissolves preferentially, which provides sufficient Mg elements for the corrosion products. Some of the Mg elements enter the corrosion products of Zn and form Zn5 (OH) 8Cl2 H _ 2O and Zn4CO3 (OH) _ 6 H _ 2O. However, the existence of Al3 and Mg2 can reduce the tendency of Zn4CO3 (OH) 6H 2O dehydration to form unprotected Zn O in the coating, increase the amount of corrosion products such as Zn5 (OH) 8Cl2 H 2O and Zn6Al2 (OH) 16CO3 4H2O, and Zn5 (OH) 8Cl2 H 2O and Zn4CO3 (OH) 6H 2O filled in the corrosion gap can further prevent the corrosion. The lower potential is obtained on the surface of the coating, and the driving force of delamination diffusion on the anode becomes smaller, which reduces the dissolution of the edge cutting position in the long corrosion process, and improves the corrosion resistance and edge cutting protection of the coating.
【作者单位】：新冶高科技集团有限公司先进金属材料涂镀国家工程实验室;国家知识产权局专利局专利审查协作广东中心;
【基金】：国家自然科学基金资助项目(51071052) 国家“十二五”科技支撑计划资助项目(2012BAJ13B03)
【分类号】：TG174.44

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