L245钢基体表面粗糙度对Ni-Sn-P化学镀层耐蚀性的影响

在不同表面粗糙度的L245钢表面获得Ni-Sn-P化学镀层。采用光学显微镜观察镀层的表面形貌;根据极化曲线、交流阻抗谱及浸泡腐蚀试验分析镀层耐蚀性。结果表明,较粗糙基体表面上的Ni-Sn-P镀层胞状物沿沟槽生长为条块状,当基体表面粗糙度Ra=0.147μm时,镀层的自腐蚀电流密度小,腐蚀速率相对较低;当基体表面粗糙度下降到Ra=0.053μm时,镀层致密性下降,耐蚀性最差。其原因是随着基体表面粗糙度的降低,镀层表面生长的条块状组织相互接合增多,产生孔隙的可能性增大。

Effect of Surface Roughness of L245 Steel Substrate on the Corrosion Resistance of Ni-Sn-P Coatings

The electroless Ni-Sn-P coating was obtained on the surface of L245 steel substrate with different surface roughness in this paper.The surface morphology of the coating was observed using an optical microscope and the corrosion resistance was examined by polarization curve,AC impedance spectroscopy and immersion corrosion test.The results indicated that Ni-Sn-P coating cell grew along the trench on the rough substrate surface to form a strip.When the surface roughness of substrate was 0.147μm,the coating had small corrosion current density and re-latively low corrosion rate.But when the surface roughness of the substrate decreased to 0.053μm,the compactness of coating decreased and corrosion resistance turned worst.The reason was that as the roughness of the substrate sur-face decreased,the strips bonded to each other growing on the surface of the coating increased,and then the possibili-ty of voids increased.