表面粗糙度对Q235钢电化学磷化膜耐蚀性的影响

Effect of Surface Roughness on Corrosion Resistance of Electrochemical Phosphate Film on Low Carbon Steel

当前的电化学磷化研究忽视了材料表面粗糙度对膜层性能的影响。分别采用机械抛光和高能喷丸对Q235钢进行前处理,并在其表面制备电化学磷化膜;采用扫描电镜、X射线衍射、硫酸铜点滴、全浸泡和极化曲线等方法分析了电化学磷化膜的形貌、组成及耐蚀性。结果表明:粗糙度较小的抛光试样表面形成了块状结晶磷化膜,粗糙度较大的喷丸试样表面形成的电化学磷化膜为细针状结晶;与喷丸处理相比,抛光处理试样表面电化学磷化膜耐蚀性更好,其硫酸铜点滴时间、盐水全浸泡时间和极化电阻分别是喷丸试样的4.0,4.0和3.7倍;喷丸试样膜层主要有Zn3(PO4)2·4H2O、Zn2Fe(PO4)2·4H2O和少量Fe相,而抛光试样中不存在Fe相,出现了耐蚀性更好的Zn3(PO4)2·2H2O相。

The surface of low carbon steel was processed by mechanical polishing and shot peening,respectively,afterwards an electrochemical phosphate film was prepared on it.The morphology,composition and corrosion resistance of the electrochemical phosphate film were analyzed by scanning electron microscope(SEM),X-ray diffraction(XRD),copper sulfate dripping test,immersion and electrochemical polarization methods.Results showed that the electrochemical phosphate film on the polishing sample was block-shaped and crystalized while the film on the shot peening sample was fine needleshaped.The corrosion resistance of the film on polishing sample was better than that of the film on shot peening sample.The copper sulfate dripping time and resistance time to salt immersion of the film on the polishing sample were both 4.0 times as long as those of the film on the shot peening sample,and the polarization resistance was 3.7 times.The film on the shot peening sample was mainly composed of Zn_3(PO_4)_2·4H_2O,Zn_2Fe(PO_4)_2·4H_2O and a little Fe phase;as for the film on the polishing sample,Fe phase was not detected while Zn_3(PO_4)_2·2H_2O phase which had the better corrosion resistance was formed.