Performance Comparison of Ag Coatings on Switch Contact between Cyanide Plating and Non-cyanide Brush Plating

Ag coatings were prepared on the surface of switch contact by typical cyanide plating and non-cyanide brush-plating. The performance of Ag coatings prepared by the two processes, including surface morphology, micro-hardness, thickness uniformity, adhesion between Ag coating and matrix and corrosion resistance in 3.5% sodium chloride solution, were tested and compared. The results showed that the micro-hardness of Ag coating by non-cyanide plating was up to 130 HV, equivalent to that of the cyanide plated silver layer, and could meet the hardness requirements in the DL/T 486-2010 standard. Spalling was not found for non-cyanide Ag coating after grid testing, indicating that the adhesion between non-cyanide Ag coating and matrix approached or reached the level of cyanide plated Ag coating. But Ag coating by non-cyanide brush plating had some pores, resulting in a corrosion rate of 59.6 μm/a in 3.5% NaCl solution. Corrosion rate of Ag coating by cyanide plating was only 1.5 μm/a in the same corrosion system. In addition, the thickness uniformity of non-cyanide plating layer was not stable.