取向硅钢表面绝缘涂层微结构与耐腐蚀性能

Microstructure and Corrosion Resistance of Surface Insulation Coating on Grain-oriented Silicon Steel

采用X射线衍射仪、扫描电镜、能谱分析仪和电化学工作站分别研究取向硅钢表面绝缘涂层的相成分、微观形貌、元素分布和耐腐蚀性能。结果表明：绝缘涂层为双层复合结构,底层为Mg_2SiO_4相,厚度为0.8μm;顶层为AlPO_4相,厚度为1.4μm;两层结合处存在0.4~0.6μm的扩散层。与只涂单层Mg_2SiO_4相的试样相比,双层涂层试样具有更高的腐蚀电位和极化电阻,更低的腐蚀电流密度,因此耐腐蚀性良好。随着浸泡时间的延长,腐蚀溶液逐渐渗透至硅钢基底,发生腐蚀反应,其腐蚀过程可以分为3个阶段。

The phase composition, morphology, element distribution and corrosion resistance of surface insulation coating on the oriented silicon steel were investigated in detail using X-ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS） and electrochemical workstation, respectively. The results show that the structure of the insulation coating is double compound layer. The bottom layer is Mg2SiO4 phase with 0.8μm thickness. The top layer is A1PO4 phase with 1.4μm thickness. There is a diffusion area with 0.4-0.6μm thick at the junction of two layers. In comparison to the sample coated single Mg2SiO4 layer, the sample coated double compound layer exhibits higher corrosion potential, higher polarization resistance and lower corrosion current density, thus leading to better corrosion resistance. With the increase of immersion time, the corrosion solution gradually permeates into the insulation coating and reaches the silicon steel substrate, and then reacts with the substrate. The corrosion process can be divided into three stages.