风沙冲蚀环境中Al-Zn-Si基涂层耐蚀性研究

Study on Corrosion Behavior of Al-Zn-Si-Based Alloy Coating in Sandstorm-Erosion Environment

采用高铝Al-Zn-Si合金粉末在Q235钢试样上制备了低温固化水性无铬合金涂层。采用扫描电镜和X射线衍射仪分析了风沙冲蚀后涂层表面的微观形貌、破损处腐蚀产物的形貌和相组成。通过全浸试验和电化学测试研究了风沙冲蚀后涂层的耐腐蚀性能。结果表明:Al-Zn-Si合金涂层冲蚀失重量随供砂量的增加而增大,并且随着冲蚀角度和风速的增大先升高后降低,有明显的峰值;风沙冲蚀后涂层的自腐蚀电位(Ecorr)和腐蚀电流密度(Icorr)均低于基体,表明涂层依然具有阴极保护作用。此外,腐蚀产物对冲蚀缺陷的自修复作用和腐蚀产物层的屏蔽作用降低了涂层的腐蚀速率,使风沙冲蚀后涂层仍然具有良好的耐腐蚀性能。

A low-temperature cured water-based chromium-free alloy coating was prepared on Q235 steel specimen by using high-chromium Al-Zn-Si powder. The surface pattern of the coating, and morphology and phase composition of corrosion product in the damaged coating were examined by means of scanning electron microscopy（SEM） and X-ray diffraction（XRD） after being sandstorm eroded. The corrosion resistance of the coating after being sandstorm eroded was investigated by full immersion test and electrochemical test. The results showed that erosion-induced weight loss increased with the increase in sand input, but first increased then decreased with the increase in erosion angle and in wind speed, there being a considerable peak value, for the Al-Zn-Si-based alloy coating. After being sandstorm eroded the both self-corrosion potential（Ecorr） and corrosion current density（Icorr） of the coating were lower than those of the substrate, indicating that the coating still services the function of cathodic protection. In addition, the coating exhibited less corrosion rate due to self-repairing effect of the corrosion product on the erosion defect and the shielding effect of the corrosion product layer, thus making it possible that the coating still has good corrosion resistance after undergoing sandstorm erosion.