(1. 湖南科技大學(xué) 機(jī)電工程學(xué)院，湘潭 411201；2. 華南理工大學(xué) 材料科學(xué)與工程學(xué)院，廣州 510640)
摘 要: 將熱鍍鋅鋼在20 g/L Ce(NO3)3·6H2O溶液(pH=4，25 ℃) 中處理10 s~24 h，獲得鈰轉(zhuǎn)化膜試樣。應(yīng)用極化曲線和電化學(xué)交流阻抗譜(EIS)研究鈰轉(zhuǎn)化膜試樣和空白熱鍍鋅試樣在5% NaCl溶液中的耐蝕性能。利用掃描電鏡(SEM)和X射線光電子能譜(XPS)研究轉(zhuǎn)化膜的形貌和組分。結(jié)果表明：經(jīng)硝酸鈰溶液處理后的鍍鋅鋼板，其腐蝕電流密度下降，極化電阻升高，同時(shí)，鋅腐蝕過(guò)程中的陽(yáng)極和陰極反應(yīng)受到抑制，腐蝕保護(hù)效率顯著提高；低頻阻抗值隨成膜時(shí)間的增加而先增大后減小，表明腐蝕電解質(zhì)在轉(zhuǎn)化膜層孔隙中擴(kuò)散的難易程度先增加后下降；當(dāng)成膜時(shí)間在30 min~1 h之間時(shí)，所得轉(zhuǎn)化膜的阻抗值最大可達(dá)8~9 kΩ·cm2，耐蝕性最佳。鈰轉(zhuǎn)化膜隨處理時(shí)間的增加首先在鋅晶粒晶界附近發(fā)生開(kāi)裂，逐漸形成“干涸的河床”樣形貌。鈰轉(zhuǎn)化膜含鈰、鋅、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)等混合組成。
關(guān)鍵字: 熱鍍鋅；鈰轉(zhuǎn)化膜；XPS；電化學(xué)行為；耐蝕性能
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
