镀锡板的电化学剥离及其耐蚀性研究

镀锡板是指两面镀有一层极薄金属锡的冷轧薄钢板,它将钢的硬度和强度与锡的抗腐蚀性和光亮的外表集于一体。实验用电化学法将镀锡板的钝化膜、纯锡层、合金层逐层剥离,通过阴极极化曲线、交流阻抗等电化学技术研究其电化学性能,用扫描电镜(SEM)观察剥离后各层的表面形貌,用X射线光电子能谱仪(XPS)对镀锡板铬酸盐钝化膜中铬元素的价态进行了分析。结果表明,电化学法剥离的效果十分理想,可以用于镀锡板表面不同层的形貌观察,同时还可以用于镀锡板的耐蚀机理研究。除掉钝化膜后,腐蚀电流密度从1.48 μA/cm²增大到3.5 μA/cm²,除掉纯锡层后,腐蚀电流密度从3.5 μA/cm²增大到18 μA/cm²,镀锡板良好的耐腐蚀性主要来源于纯锡层和钝化膜的作用。镀锡板铬酸盐钝化膜中铬元素主要以氢氧化铬、金属铬和三氧化二铬等形态存在。

Electrochemical stripping of tinplate and analysis of corrosion resistance property

The tinplate was a kind of cold-rolled thin steel sheet. Both sides were plated with a very thin layer of metallic tin. The hardness and strength of steel as well as corrosion resistance and bright appearance of tin were integrated. The passive film, pure tin layer and alloy layer on tinplate were stripped off layer by layer using electrochemical method.The electrochemical property was studied by means of electrochemical techniques such as polarization curves and alternating-current impedance. The surface morphology of each layer was observed by scanning electron microscope (SEM). The chemical valence of chromium in passive film of tinplate was analyzed by X-ray photoelectron spectroscopy (XPS). The results showed that the electrochemical stripping results were very good. The surface morphology of each layer could be well observed. Moreover, the corrosion resistance property of tinplate could be also investigated. After removing pure tin layer, the corrosion current density increased from 3.5 μA/cm² to 18 μA/cm². Good corrosion resistance property of tinplate was due to the pure tin layer and passive film. The chromium in passive film of tinplate mainly existed in form of chromium hydroxide, metallic chromium and chromium sesquioxide.