化学沉积Ni-Zn-P合金制备和腐蚀性能研究

PREPARATION AND CORROSION PROPERTIES OF ELECTROLESS Ni-Zn-P ALLOY DEPOSITS

采用柠檬酸钠为络合剂 ,在氨性缓冲介质中化学镀Ni Zn P合金 .考察了工艺参数 (pH、ZnSO4·7H2 O浓度和温度 )对沉积速度和镀层组成的影响 .发现Zn离子在沉积过程中起阻碍作用 ,致使镀层中Zn含量不高 (最多含16 .0mass% ) .采用差示扫描量热 (DSC)和X射线衍射 (XRD)技术研究所得化学镀Ni Zn P合金 (Ni=78.7mass % ,Zn =11.7mass % )的晶化行为和结构 .结果表明 ,镀态Ni Zn P合金主要由非晶相和少量立方镍两相构成 .热处理至 384 .8℃时出现四方Ni3 P相 ,至 5 80 .7℃时出现Ni5Zn2 1相 .镀态及热处理后的Ni Zn P合金 (Ni=78.7mass% ,Zn =11.7mass% .)在 3.5 %NaCl中 (pH =7.0 )的腐蚀失重及阳极极化测量 .结果表明 ,该合金的耐腐蚀性能优良 ,特别是镀态Ni Zn P合金 .

Electroless Ni-Zn-P alloy deposits from an alkaline bath containing NH 4Cl as a buffer agent and sodium citrate as a complexing agent was investigated.The effects of deposition parameters(pH,concentration of ZnSO 4 ·7H 2O and temperature) on the plating rate and the deposit composition was examined respectively.It was found that the presence of zinc in the bath has an inhibitory effect on the alloy deposition.As a consequence,the percentage of zinc in the electroless Ni-Zn-P alloys never reaches high values.The structure and the crystallization behavior of the deposit has been characterized by XRD and DSC.The results show that the as-plated deposits consist of mainly an amorphous structure together with some cubic phase Ni.The deposits crystallized into Ni 3P at 384.8℃ and transformed into Ni 5Zn 21 at 580.7℃.The weight loss test and the anodic polarization measurements of the as-plated and the heat-treated deposits in 3.5mass% NaCl solution (pH7.0) indicate that the two deposits show good corrosion resistance,especially the as-plated deposit.