AZ91D镁合金化学镀Ni-P及Ni-W-P镀层的结构与耐蚀性

STRUCTURE AND CORROSION RESISTANCE OF ELECTROLESS PLATING Ni-P AND Ni-W-P COATINGS ON AZ91D MAGNESIUM ALLOY

在AZ91D镁合金上直接化学镀Ni-P和Ni-W-P镀层,并利用扫描电子显微镜、X射线衍射仪及电化学工作站研究后续热处理对化学镀层组织形貌、相组成及其耐蚀性的影响。结果表明,制备的Ni-P镀层为非晶态,而Ni-W-P镀层为纳米晶结构,两者在3.5%NaCl水溶液中的耐蚀性相当。热处理可以明显提高Ni-W-P镀层的耐蚀能力,但却稍微弱化Ni-P镀层的耐蚀能力,热处理后的Ni-W-P层自腐蚀电位相对于未处理的化学镀Ni-W-P或Ni-P层提高了约150 mV。

Ni-P and Ni-W-P coatings were prepared on AZ91D magnesium alloy by a direct electroless plating processing.The microstructure,phases and corrosion resistance of the prepared and post-annealed coatings were studied by using scanning electron microscopy,X-ray diffraction technique and electrochemical test.The results show that the Ni-P coating is of amorphous structure while the Ni-W-P coating is of nanocrystalline structure with a grain size of about 7 nm,and they have similar corrosion resistance against 3.5%NaCl aqueous solution. The corrosion potential of the Ni-W-P coating after annealing at 250℃for 50 min positively shifts by 150 mV as compared to that of as-prepared Ni-W-P or Ni-P coating,implying the corrosion resistance of the annealed Ni-W-P coatings has been much improved.