热镀锌铝镁镀层的切边保护性能和耐腐蚀机理  

Cut-edge protection performance and corrosion resistance mechanisms of galvanized Zn-Al-Mg alloy coating

作　　者：袁训华 林源[2] 张启富 

机构地区：[1]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,北京100081 [2]国家知识产权局专利局专利审查协作广东中心,广州510530

出　　处：《中国有色金属学报》2015年第9期2453-2463,共11页The Chinese Journal of Nonferrous Metals

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)

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。The microstructure and surface morphology after corrosion of the hot-dip galvanizing alloy coating with different components were observed by scanning electron microscopy, the corrosion performance and corrosion resistance of coating were analyzed by the electrochemistry and cyclic corrosion test, and the phase composition of corrosion product on the coating surface was analyzed by X-ray diffractometry. The results show that the corrosion current density of galvanized Zn-Al-Mg alloy coating is lower than that of zinc coated steel in electrochemical test, which proves that the existing of aluminum, magnesium and Zn2Mg phase can make the stable compounds form on the surface of coating and reduce the dissolution rate of zinc. The eutectic phase can make the Mg element uniformly distribute in the galvanized Zn-A1-Mg alloy coating, and inhibit the cathode reaction. Zns（OH）8C12·H2O and Zn6Al2（OH）16CO3·4H2O are insoluble colloidal corrosion products of galvanized Zn-Al-Mg alloy coating after corroded, which can cut off the electronic transmission between coating and external substance, effectively. Zn2Mg is dissolved preferentially in the initial corrosion, which provides enough Mg elements for the corrosion products, part of Mg elements dissolve from the surface of coating, get into the corrosion products of zinc, and form Zns（OH）8C12·H20 and Zn4CO3（OH）6·H2O. However, the exist of A13＋ and Mg^2＋ can reduce the trend that Zn4CO3（OH）6·H2O dehydrated to from zinc oxide without protective effect, and increase the amount of Zns（OH）8Cl2-H2O and Zn6A12（OH）I6CO3·4H2O in galvanized Zn-A1-Mg alloy coating. And the chemical compound of Zns（OH）8Cl2·H20 and ZnaCO3（OH）6·H20 can be full in the corrosion cracks that furthermore prevent corrosion occurring in the coating, so, the lower potential is obtained on surface of coating, thus, the hierarchical diffusion driving force of anode becomes small, which can reduce the dissolution of cut-edge part of galvanized Zn-Al-Mg alloy coating in

关 键 词：热镀锌铝镁镀层 显微组织 电化学 循环腐蚀试验 切边保护性能 耐腐蚀机理 

分 类 号：TG174.44[金属学及工艺—金属表面处理]