There are many customers who find that there will be white spots in the process of electroplating precision stainless steel strips, and they do not know the reason and what to do. The white spots appearing in electroplating nickel are caused by a high carbon material, which is produced by the heat treatment carburizing process and the pickling process during the pre-electroplating treatment. There are two general reasons:
(1) The carbon (mainly Fe, C) of the surface layer of the precision stainless steel belt after normal carburization can reach 0.8 to 1.2, and the particles protruding in the coating layer are due to the incomplete pretreatment cleaning, so that the particles on the surface of the workpiece fall into the plating solution In the electroplating process, due to the stirring effect, these particles freed in the plating solution co-deposit with nickel ions.
(2) The holes that are not covered in the coating are mainly caused by over-corrosion (surface decarburization) during the pretreatment pickling process. The main components of the pickling solution of the electroplating plant are HCl 1:1; H2SO4 (98%) 50 mL/L; this formula is OK for ordinary carbon steel, but the concentration is too high for high carbon steel. The higher the carbon content, the more severe the pickling reaction. After the surface is decarburized, it has a great influence on the conductivity of the workpiece and the adhesion of the coating. The holes in the coating are actually caused by the poor conductivity (or poor adhesion) of the high carbon part, and the coating is difficult to cover.
By taking the following measures, the white spot problem of the precision stainless steel strip has been fundamentally solved：
(1) Improve the pretreatment and cleaning process, and use the ultrasonic cleaning method to make the particles with poor adhesion after carburizing fall off during cleaning.
(2) Filter the plating solution in time.
(3) Improve the pickling process: mainly reduce the concentration of the pickling solution, add a suitable corrosion inhibitor and properly control the pickling time to avoid over-corrosion.