元素W与Mo对非晶Ni-P镀层热稳定性和耐腐蚀性能的影响

Effect of W and Mo on Thermal Stability and Corrosion Resistance of Amorphous Ni-P Coating

本研究利用化学镀方法分别制备出P含量基本一致的非晶Ni-P镀层、非晶Ni-W-P镀层和非晶Ni-Mo-P镀层。P含量基本一致,保证了三种镀层的非晶化程度相差不大。在该条件下,分别对镀层进行DSC测试,获取镀层放热峰的变化情况并计算出相应的表观晶化激活能,结果获知添加元素W和Mo可以提高非晶Ni-P镀层的热稳定性能。随后对三种镀层分别进行200℃-4 h、300℃-4 h、400℃-4 h的热处理,通过分析镀层的XRD曲线来进一步确认W和Mo能够提高Ni-P镀层的热稳定性能。利用电化学工作站测定三种非晶镀层在3.5%(质量分数)氯化钠溶液中的极化曲线,借助Tafel方法计算镀层的腐蚀参数,进而判断添加元素W和Mo可以提高非晶Ni-P镀层的耐腐蚀性能。利用SEM方法分析镀层腐蚀后的表面形貌,利用XPS方法对腐蚀后的产物进行分析,推测W元素和Mo元素提高镀层耐腐蚀性能的原因应该是,镀层表面形成的W和Mo元素的氧化物较为有效地阻止了氯离子的穿孔腐蚀。

Amorphous Ni-P coating,Ni-W-P coating and Ni-Mo-P coating with almost the same P content that means almost the same amorphous degree were prepared through electroless plating method.DSC tests were carried out to obtain the exothermic peaks of the three amorphous coatings and the corresponding apparent crystallization activation energy.Results showed that the addition elements W and Mo could improve the thermal stability of amorphous Ni-P coating.Then the three kinds of amorphous coatings were subjected to heat treated at 200℃-4 h,300℃-4 h and 400℃-4 h respectively.By analyzing the XRD curves of these annealed coatings,it was further confirmed that elements W and Mo could improve the thermal stability of Ni-P coating.The polarization curves of three amorphous coatings in 3.5wt%sodium chloride solution were mea-sured by electrochemical workstation.The corrosion parameters of these coatings were calculated by Tafel method.Results showed that the corrosion resistance of amorphous Ni-P coating could be improved by adding elements W and Mo.The surface morphology of the three amorphous coatings after corrosion were analyzed by SEM method,and the corrosion products were analyzed through XPS method.It was speculated that the reason for corrosion resistance improvement of the amorphous Ni-P coating by W and Mo elements was the oxides of W and Mo,which were formed on the coatings surface.These oxides could effectively prevent the perforation corrosion of chloride ions.