Because of powder metallurgy products contain a certain porosity, direct plating could’t reach a good surface quality, while remaining in part the pores plating solution is difficult to remove and cause internal corrosion. Secondly, during the electroplating process, when the article from one tank to another tank when the liquid remaining in the pores of the solution can contaminate the other groove. After plating powder metallurgy, the pores will raffinate bleed plating, so that the surface pitting.
Mechanical sealing method: parts have greater finishing allowance, by finishing the closed surface pore. Also available through other mechanical methods of surface deformation and closed pore, such as sandblasting, grinding and polishing.
Fixed substance blocking method: in 200 DEG C parts to be immersed in the molten zinc stearate, which infiltrate into the pore of sealing hole, after soaking should remove the surface excess zinc stearate, then electroplating. Vacuum impregnating resin, high soft point paraffin is a feasible and simple method.
Steam treatment method: steam processing in the parts surface to form a layer of Fe3O4 oxide film, can clog the surface pore. Fe3O4 is a compact semiconductor, does not prevent electroplating. Steam treatment before plating parts, without any cleaning process.
Organosilicon compounds plugging method: the part is immersed in carbon tetrachloride solution containing 4% of the organosilicon compounds. Part preheated to 200 ℃, then suddenly immersed in the solution. And then soaked at 200 ℃ under drying. In part this may be formed on the surface layer of organic silicide film, can play a role in preventing the intrusion of plating solution. This method of nickel, cadmium have satisfactory results