Stainless steel parts (drive shaft, meshing parts, moving parts, etc.) Electroless nickel plating, can improve the coating uniformity and self-lubricating, better than electrochromic chrome. But stainless steel chemical nickel often due to poor pre-treatment caused by the coating and the substrate bonding force is not ideal, the actual production of an urgent need to solve the problem.
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: HCL descaling alone is not effective; complex shape pieces of flash nickel plating due to poor coverage and affect the uniformity of electroless nickel plating; longer process may result in fresh stainless steel surface is re-oxidized into Film; Nickel plating solution easy to pollute electroless nickel solution. To this end, some people improve the process.
Improve the process: Polishing, degreasing process with the original process → mixed acid removal membrane (25% HCl + 8% HNO3 + 10% HF) → cold water washing → activation (10% HCl +5% NH4F, 60 ℃) → hot water washing → Electroless Nickel.
Improve the advantages of the process: ① mixed with acid to remove the insoluble stainless steel surface FeCrO4 oxide film, Si, SiO2, so that the chemical activity of the substrate surface enhanced; ② process simplification, to avoid the stainless steel fresh surface re-oxidized; ③ increase the substrate preheating process , To eliminate the coating and the substrate due to temperature stress and stress. Therefore, the combination of electroless nickel plating and the substrate is good, rapid plating and so on.
Article from NdFeB Industry Network