The pretreatment process is the key procedure to determine the quality of Ni-p plating of high strength bolts, the aim of which is to remove the passivation layer of the bolt surface and prevent the regeneration of the passivation film. The implementation of the process directly determines the combination of the matrix and the coating quality degree. Most of the quality accidents that occur in the production are caused by the improper handling of the bolts. The oil, rust and oxidized skin attached to the surface of bolts must be carefully removed before plating. The difference with electroplating is that it should be examined more carefully, and the bolts for handling the net are absolutely not allowed to be coated.
① bolts Inspection; Visually inspect the surface quality of bolts and require that any burr left by machining must be removed, and sharp edges shall be rounded.
② manual oil removal, ensure the substrate surface without grease.
③ soak and remove oil, put bolts into alkaline water and boil to remove oily surface.
④ acid pickling; In order to prevent the alkaline oil-removing solution from polluting the flashing nickel plating bath, the pickling solution is used for electric activation treatment before flashing nickel plating.
⑤ is electrically activated and electrically activated with acid solution.
⑥ Flash nickel plating on low alloy steel should be used to increase the bonding strength between the coating and the substrate.