(1. 湖南科技大学 机电工程学院，湘潭 411201；2. 华南理工大学 材料科学与工程学院，广州 510640)
摘 要: 将热镀锌钢在20 g/L Ce(NO3)3·6H2O溶液(pH=4，25 ℃) 中处理10 s~24 h，获得铈转化膜试样。应用极化曲线和电化学交流阻抗谱(EIS)研究铈转化膜试样和空白热镀锌试样在5% NaCl溶液中的耐蚀性能。利用扫描电镜(SEM)和X射线光电子能谱(XPS)研究转化膜的形貌和组分。结果表明：经硝酸铈溶液处理后的镀锌钢板，其腐蚀电流密度下降，极化电阻升高，同时，锌腐蚀过程中的阳极和阴极反应受到抑制，腐蚀保护效率显著提高；低频阻抗值随成膜时间的增加而先增大后减小，表明腐蚀电解质在转化膜层孔隙中扩散的难易程度先增加后下降；当成膜时间在30 min~1 h之间时，所得转化膜的阻抗值最大可达8~9 kΩ·cm2，耐蚀性最佳。铈转化膜随处理时间的增加首先在锌晶粒晶界附近发生开裂，逐渐形成“干涸的河床”样形貌。铈转化膜含铈、锌、氧等元素，主要由CeO2、Ce(OH)4(或CeO2·2H2O)、ZnO和少量Ce2O3、Ce(OH)3(或Ce2O3·2H2O)等混合组成。
关键字: 热镀锌；铈转化膜；XPS；电化学行为；耐蚀性能
cerium conversion coating on hot-dip galvanized steel
（1. College of Electromechanical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China;
2. School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China）
Abstract:The cerium conversion coatings were prepared on hot-dip galvanized (HDG) steel sheets treated in 20 g/L Ce(NO3)3·6H2O solution (pH = 4, 25 ℃). The corrosion electrochemical behavior of the cerium conversion coatings was compared with that of blank hot-dip galvanized sample in 5% NaCl solution using polarization curves and electrochemical impedance spectra (EIS). The morphology and composition of the coatings were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results show that the corrosion current density of the HDG decreases and the polarization resistance increases after cerium nitrate conversion treatment. While the cerium conversion coatings can markedly restrain the anodic and cathodic reaction during the zinc corrosion process, thereby its corrosion protective efficiency remarkably increases. It is also found that the low-frequency impedance initially increases and then decreases with the treatment time increasing, which demonstrates clearly that the resistance to the migration of electrolyte through the conversion coatings initially increases and subsequently decreases with the treatment time increasing. When the treatment time is prolonged from 30 min to 1 h, the maximal impedance of the conversion coating is up to 8−9 kΩ·cm2 and its corrosion resistance is optimal. The cerium conversion coating is apt to crack in the vicinity of zinc grain boundaries, and the dry riverbed morphology gradually forms with the treatment time increasing. The cerium conversion coating is composed of Ce, Zn and O elements, which mainly consists of CeO2, Ce(OH)4 (or CeO2·2H2O), ZnO and a small quantity of Ce2O3, Ce(OH)3 (or Ce2O3·2H2O).
Key words: hot-dip galvanizing; cerium conversion coating; XPS; electrochemical behavior; corrosion resistance
