pH值对AM60B镁合金化学镀镍的影响

Effects of pH Value on Electroless Ni Plating on AM60B Magnesium Alloy

摘要:

以碱式碳酸镍为主盐，NaH2PO2为还原剂，在铸态AM60B镁合金上化学镀镍。采用X射线衍射仪（XRD）、显微硬度计、金相显微镜及电化学工作站等，研究了pH值对镁合金化学镀镍的影响。结果表明：pH值由6.0增加到7.0，镀层镀速增加。3种pH值下沉积的镀层都为胞状结构，且pH值为6.5时，颗粒最小且致密均匀。 pH值由6.0增加到7.0，得到的镀层磷含量降低，且显微硬度降低，pH值为6.0时镀层硬度HV最高达到5400 MPa。3种pH值下都能得到完整的化学镀镍层，镍的主峰比较宽，第2及第3强峰基本没出现。耐蚀性试验结果表明，pH为6.5时得到的镀镍层耐蚀性最好，自腐蚀电位最高为–0.90 V。

Abstract:

The electroless nickel plating of as-cast AM60B magnesium alloy was carried out using NiCO3·3Ni(OH)2·4H2O as main salt and sodium hypophosphite as reductant. The influence of pH value on the microstructure, microhardness and electrochemical properties of the electroless Ni plating was studied using X-ray diffractometer (XRD), microhardness device, metallograph and electrochemical station. The results show that the deposition rate of the electroless Ni plating increases when the pH value increases from 6.0 to 7.0. The electroless coating is composed of cell structures. When the pH is 6.5, the electroless Ni coating is compact and the particle is smallest. The microhardness and the P content are reduced with the pH value increasing from 6.0 to 7.0. When the pH value is 6.0, the microhardness HV is highest and gets to 5400 MPa. At the three pH values, the electroless Ni coating is integrated; the main peak of Ni is wider, while there are nearly no second or third peaks. When the pH value is 6.5, the corrosion electric potential of plating is up to –0. 90 V, and the corrosion resistance is best.