【作者】 杜鸿雁；

【导师】 李焰； 张胜涛；

【作者基本信息】 重庆大学 ， 应用化学， 2004， 硕士

【摘要】 海水中，镀层金属（或合金）对钢铁基体的保护作用主要有两个方面，首先是海水腐蚀初期镀层的自腐蚀和锈层腐蚀产物的保护性，其次是随着腐蚀的进行，锌（或锌铝多元合金）镀层缺陷处的钢基作为阴极受到镀层的保护。目前，国内外学者已经对合金镀层的全面腐蚀行为进行了系统、深入的研究，但是，镀层金属（或合金）对基体的牺牲阳极保护作用迄今仅有定性研究。因此，本课题按照规范的牺牲阳极电化学性能试验方法对几种典型热浸镀金属(合金)在海水中对钢铁基体的牺牲阳极保护性能进行了定量的研究，旨在为新型耐海水腐蚀镀层材料的开发提供指导性数据和科学依据。 本文自制了9种锌及锌铝合金试样，首次按照规范要求分别在20℃、35℃、50℃下通过实验系统地测定了开路电位、工作电位、阳极消耗率、镀层消耗厚度以及电流效率等定量描述牺牲阳极性能的电化学参数；在海水环境条件下观察了腐蚀产物脱落情况及腐蚀均匀性；结果表明锌的牺牲阳极保护性能最优，而Zn-55Al-1.6Si合金的保护性能最差，其余合金的电化学保护性能介于二者之间；随着温度的升高，各试样的阳极保护性能均变差。从而证明：虽然在腐蚀实验初期，铝含量越高的合金镀层的腐蚀速度越小，但是腐蚀后期，铝含量越高越不利于对钢铁基体的保护。为了从微观角度探究合金电流效率降低的原因，本论文特应用扫描电子显微镜观察了50℃下腐蚀实验结束后腐蚀严重的Zn-30Al-0.2Mg-0.2Si、Zn-30Al-0.2RE-0.2Si和Zn-55Al-1.6Si合金截面，结果表明铝含量高的合金晶界腐蚀显著加重，论文就铝元素对牺牲阳极性能的影响进行了分析和理论解释。 本论文还应用灰箱分析法研究了所选择的五类元素形成合金后与开路电位、工作电位、阳极消耗率、镀层消耗厚度、电流效率和腐蚀均匀性的关联度。结果表明，Zn对各性能的影响均最显著，Al、Si对开路电位、工作电位、阳极消耗率、镀层消耗厚度、电流效率的影响大于Mg和RE(稀土)；而对于提高合金的腐蚀均匀性来说，Mg的影响却大于Al、Si和RE。由此得出：Zn是提高合金对钢铁基体牺牲阳极保护作用的最主要因素，而Al的存在会降低合金的电化学保护性能，同时，添加过量的Mg元素也会降低合金的保护性。更多还原

【Abstract】 In the seawater, Zn-Al alloy coatings protect steel substrate. On the initial stage, Zn-Al alloy coatings and corrosion products make the steel subject insulated from seawater. With the corrosion going on, the flaws in the coatings get the steel substrate exposed to seawater. At the same time, the steel substrate is protected by the coating as an anode. Presently, many scholars have studied the uniform corrosion of the coatings. However, the cathodic protection of the coating has only been studied qualitatively. Therefore, the dissertation evaluated the cathodic protection qualificationally according to the sacrificial anode electrochemical test standard, which would provide scientific data to the new corrosion resistant coatings in seawater.Nine types of alloys were made and according to the standard of GB 17848-1999, their potentials were tested, their anode depletion rate ,coating consume thickness and current efficiencies were calculated and their corrosion products’ falling off and corrosion uniformity were observed at 20℃,35℃ and 50℃. It was shown that Zn is the best in the electrochemical protection performance, Zn-55Al-1.6Si is the worst, and the others are between them. It was also indicated that with the temperature rising, the electrochemical protection performance for all specimens become worse. Therefore, it was proved that though on the initial stage, the more Al, the lower corroding rate, on the late stage, the high content of Al is disadvantage to protect the steel substrate. In order to study the reason of the low current efficiency, the sections of Zn-30Al-0.2Mg-0.2Si, Zn-30Al-0.2RE-0.2Si and Zn-55Al-1.6Si were observed by the scanning electron microscope (SEM) after the experiments at 50℃. It was figured that the grain-boundry corrosion is more serious with the more Al. The influence of Al to sacrificial anode property was analyzed and explained theoretically.Mathematical grey-box interrelation analysis method was used to study the correlation between five selected alloy elements and open circuit potential, working potential, anode depletion rate, coating consume thickness, current efficiency and corrosion uniformity. It was showed that Zn is the most important factor to affect alloys’ cathodic protection performance, while Al and Si are inferior to Zn. It was indicated that Mg is the key element to affect corrosion uniformity of alloys. Therefore, It was educed <WP=6>that Zn is the best element for improving the alloy’s electrochemical protection performance, Al is the worst, and more Mg will decrease the property.更多还原