NdFeB plating: NdFeB plating process
NdFeB plating products according to the use of different environments and different rhyme plating process, the surface coating is also divided into two categories, one is galvanized for conventional products; the other is nickel-plated, for higher requirements The product. There are also a few products starting from the whole machine requires plating other plating, such as plating alloy, silver and so on.
NdFeB galvanized products using the first chemical zinc and then galvanized process.
① chemical leaching zinc: zinc sulfate 35g / L potassium fluoride l0g / L potassium pyrophosphate l20g / L temperature 90 ℃ sodium carbonate l0g / L time 40s
Potassium chloride bright galvanized: Potassium chloride 180 --- 200g / L pH value 5.0 ~ 5.5 Zinc chloride 60 ~ 80g / L Temperature Room temperature Boric acid 25 ~ 35g / L Current density l ~ 2A / dm2 Commercial brightener press Instructions to join
③ plating treatment: The neodymium iron boron products must pass through passivation treatment, can be low-chrome or trivalent front, chrome passivation, and then after drying the surface coated with light coating. Color passivated neutral salt spray test requirements of not less than 72h.
(2) Nickel plating
NdFeB nickel plating is actually multi-layer coating, the need to pre-nickel plating, and then thickening by copper plating, and then coated bright nickel surface.
Pre-nickel plating: nickel sulfate 300g / L pH value 4.O ~ 4.5 Nickel chloride 50g / L Temperature 50 ~ 60 ℃ Boric acid 40g / L
Current density of 0.5 ~ 1.5A / dm2 additive amount of time 5min
② pyrophosphate copper thickening: as the intermediate coating, although the popular acid bright copper plating process, but for neodymium iron boron material, thick plating should not be used acid copper plating, which is because in the strong acid bath, has been Pre-plated cathode coating of porous materials will be prone to micro-corrosion matrix; delay bubble later left hidden dangers. More appropriate process is close to neutral pyrophosphate copper plating.
Copper pyrophosphate 70g / L Brightener qs Potassium pyrophosphate 300g / L pH 8 ~ 8.5 Ammonium citrate 30g / L Temperature 40 ~ 50 ℃ Ammonia 3mL / L Current density l ~ 1.5A / dm2
③ bright nickel plating
Nickel sulfate 300g / L Commercial Brightener Add nickel chloride according to instructions 40g / L pH 3.8 ~ 5.2 Boric acid 40g / L Temperature 50 ℃ Low foam wetting agent lmL / L Cathode current density 2 ~ 4A / dm2
For neodymium iron boron materials that require other surface coatings, additional surface plating may be performed after the copper plating of the intermediate plating has been completed. Sometimes in order to increase the thickness and reliability of the coating, you can also add rapid acid copper plating process after pyrophosphate coating, in order to obtain good surface decoration, and then plating other coatings will have better results. The key point for these plating operations is that it must be energized and can not be de-energized in the middle of the tank. Otherwise, the plating solution in the pores will also cause micro-corrosion on the substrate and affect the bonding force.
Article from NdFeB Industry Network