How to improve the bonding force of electroless nickel plating on stainless steel

Electroless nickel plating of stainless steel parts (drive shafts, meshing parts, moving parts, etc.) can improve the uniformity and self-lubricity of the plating, which is better than chromium plating. However, electroless nickel plating on stainless steel often results in unsatisfactory bonding between the plating layer and the substrate due to poor pretreatment, which has become an urgent problem in actual production.

The original process: mechanical polishing→organic solvent degreasing→chemical degreasing→hot water washing→electrochemical degreasing→hot water washing→cold water washing→30%HCl→cold water washing→20%HCl(50℃)→cold water washing→flash plating Nickel → electroless nickel plating.

Disadvantages of the original process: the effect of using HCL alone to remove the oxide scale is not good; the flash nickel plating of complicated shapes affects the uniformity of electroless nickel plating due to poor coverage; the longer process may cause the fresh surface of stainless steel to be re-oxidized. Film; flash nickel plating solution is easy to pollute chemical nickel plating solution, etc. To this end, someone improved the process.

Improved process flow: the polishing and degreasing process is the same as the original process → mixed acid removal film (25%HCl+8%HNO3+10%HF) → cold water washing → activation (10%HCl+5%NH4F, 60℃) → hot water washing → Electroless Nickel.

The advantages of the improved process:

1. Use mixed acid to remove the insoluble FeCrO4 oxide film, Si, SiO2 on the surface of the stainless steel, and enhance the chemical activity of the surface of the substrate，
2. The process is simplified to avoid the fresh surface of the stainless steel from being re-oxidized，
3. The preheating process of the substrate is increased , Eliminate the stress caused by the temperature difference between the plating layer and the substrate. Therefore, the electroless nickel plating has a good bonding force with the substrate, and the plating speed is fast.