Glycerol Effect on the Corrosion Resistance and Electrodeposition Conditions in a Zinc Electroplating Process

Zinc electrodeposition is an economical process of Zn coating compared to conventional galvanic process. The galvanizing process is used in various industrial sectors to protect ferrous alloys during the corrosion process. In buildings, the galvanizing process is widely used to coat mortar protective screens. The electrodeposition of zinc has a relatively low cost compared to other coating materials for the same purpose; however, its corrosion resistance is lower than that of most protective deposits. This study evaluated the effect of adding glycerol to the electrodeposition bath on the corrosion resistance, deposition efficiency, morphology and microstructure of the zinc electrodeposit in concentrations ranging from 0.03 to 0.82 M. The electrodeposition was performed on carbon steel AISI 1020 with a current density of 10 mA.cm-2. The electroplating solution composition was 0.10 M ZnCl2, 2.80 M KCl and 0.32 M H3BO3. Electrodeposition time was 17.56 min, 5 µm thick coating, equivalent to the mass of 7.166E-3 g of zinc on the steel surface. Evaluation of the corrosion resistance was performed by means of the electrochemical tests of Anodic Voltammetry, Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) as well as Weight Loss tests in NaCl 0.5 M in 4 (four) different period of immersion. The morphology and microstructures of electrodeposited were analyzed using the techniques of Scanning Electron Microscopy (SEM) and Spectrometry X-Ray Diffraction (XRD). The presence of glycerol in the electrodeposition bath decreased the deposition efficiency; however, it increased corrosion resistance and promoted the formation of more compact and refined electrodeposited coatings. Moreover, the results showed that the corrosion rate does not vary linearly with the addition of glycerol.

与传统镀锌工艺相比，锌电沉积是一种更为经济的锌涂层制备工艺。镀锌工艺广泛应用于各类工业领域，用于在腐蚀环境中保护铁合金构件。在建筑领域，镀锌工艺被广泛用于砂浆防护屏的涂层制备。相较于同用途的其他涂层材料，锌电沉积工艺的成本相对较低，但其耐腐蚀性能却低于多数防护镀层。本研究针对浓度范围为0.03~0.82 M的甘油添加剂，探究其添加至锌电沉积镀液后，对锌镀层的耐腐蚀性能、沉积效率、表面形貌与微观结构的影响。实验以AISI 1020碳钢为基底，采用10 mA·cm⁻²的电流密度开展锌电沉积。电镀液的组成如下：0.10 M氯化锌（ZnCl₂）、2.80 M氯化钾（KCl）与0.32 M硼酸（H₃BO₃）。电沉积时长为17.56 min，所得镀层厚度为5 μm，对应钢表面沉积的锌质量为7.166×10⁻³ g。耐腐蚀性能评价采用了阳极伏安法、动电位极化法与电化学阻抗谱（Electrochemical Impedance Spectroscopy, EIS）等电化学测试手段，同时在0.5 M氯化钠溶液中开展了4组不同浸泡时长的重量损失实验。采用扫描电子显微镜（Scanning Electron Microscopy, SEM）与X射线衍射（X-Ray Diffraction, XRD）技术对镀层的形貌与微观结构进行表征分析。镀液中添加甘油会降低沉积效率，但可提升镀层的耐腐蚀性能，并促进形成更致密、更细化的锌镀层。此外，实验结果表明，镀层腐蚀速率并非随甘油添加量呈线性变化。