烧结NdFeB磁体表面化学镀Ni-Cu-P合金及防腐性能

在烧结NdFeB磁体表面化学镀Ni-Cu-P以提高其耐腐蚀性能. 研究了络合剂的质量浓度、镀液的pH值、施镀温度及金属离子配比Cu2 ]/Ni2 ]对沉积速度和镀层成分的影响. 用扫描电镜(SEM)和能谱仪(EDAX)观察镀层形貌并分析镀层成分. 测定Ni-Cu-P合金镀层在质量分数3.5% NaCl溶液中的极化曲线,并结合中性盐雾实验表征镀层的耐腐蚀性能. 研究表明:烧结NdFeB永磁体经碱性超声波除油、酸洗活化后进行化学镀Ni-Cu-P,可得到结合力良好的合金镀层;随着镀液中金属离子配比Cu2 ]/Ni2 ]的增大,所得镀层从非晶向晶态转变,镀层中的磷含量先升高后降低,镀层表面变得平整、致密;化学镀Ni-Cu-P三元合金的耐腐蚀性能优于相同条件下所得到的Ni-P镀层,且从金属离子配比(Cu2 ]/Ni2 ])为0.02的镀液中得到的镀层的耐腐蚀性能最强.

Anti-corrosion properties of electroless Ni-Cu-P ternary deposits on sintered NdFeB magnets

Electroless plating of a Ni-Cu-P ternary alloy was carried out on sintered NdFeB magnets to improve their corrosion resistance.The effects of complexing agent concentration,metallic-ion ratio Cu 2 ]/Ni 2 ],pH value,and temperature on the deposition rate and coatings' composition were studied.Surface morphologies of the coatings were observed through SEM(Model FEI SIRION),and the element composition of the coatings was analyzed through EDAX.The corrosion resistance of the Ni-Cu-P ternary alloy was investigated through polarization curves in a 3.5% NaCl solution and neutral salt spray tests.The results show that good adhesion of the Ni-Cu-P deposits to the magnets can be achieved after ultrasonic cleaned with alkaline solution and activated by acid;with increasing Cu 2 ]/Ni 2 ],the deposits transformed from amorphous to crystalline and became more smooth and compact,the phosphorus content of the deposits firstly increased then decreased.It is indicated that the electroless deposits on sintered NdFeB surface exhibited a superior corrosion resistance than electroless Ni-P deposits;the corrosion resistance of the Ni-Cu-P ternary alloy obtained from the solution with a metallic-ion ratio of 0.02 was the best.