Titanium alloy nickel plating is usually carried out by the chemical nickel plating method. The specific process flow is generally as follows:
Sandpaper polishing:
Use sandpaper to polish the surface of the titanium alloy. The purpose is to remove burrs, oxide scales, etc. on the surface, increase the surface roughness, and enhance the adhesion of the coating.
Deionized water washing:
Rinse the polished titanium alloy workpiece with deionized water to remove the remaining grinding debris and impurities on the surface.
Deoiling:
Immers the workpiece in a solution composed of 70g/L NaOH, 30g/L Na₂CO₃, 30g/L Na₃PO₄, and 7g/L Na₂SiO₃ at 80°C for 10 minutes to remove surface oil stains.
Deionized water washing: Rinse the workpiece again with deionized water to thoroughly remove the deoiling agent and decomposition products of oil stains, etc.
Acid etching:
The workpiece can be immersed in a solution consisting of 100mL/L hydrochloric acid, 200mL/L nitric acid, and 100mL/L hydrofluoric acid, or 200mL/L nitric acid and 200mL/L hydrofluoric acid, and treated at room temperature for 120 seconds to remove the surface oxide film and activate the surface.
Deionized water washing:
Wash the acid-etched workpiece to remove the residual acid solution and prevent it from affecting the subsequent processes.
Immersion zincating:
Immers the workpiece in zincating solution, such as "hydrofluoric acid 70mL/L, ZnSO₄ 12g/L" or "NaOH 120g/L, ZnO 20g/L, potassium tartrate 50g/L, additive A 2g/L, additive B 1g/L", and soak for an appropriate time at room temperature, forming a thin zinc layer on the titanium alloy surface to prevent re-oxidation of the substrate and activate it.
Deionized water washing:
Rinse the workpiece to remove the residual impurities and unreacted reagents during zincating.
Retraining zinc:
Put the workpiece into a 500mL/L nitric acid solution and treat it at room temperature for 15 seconds to remove the relatively loose zinc layer that was first immersed.
Deionized water washing:
Clean the workpiece to remove zinc ions and residual nitric acid produced during retraining zincation.
Secondary zincating:
Immers the workpiece again in the zincating solution to obtain a denser and more uniform zinc layer, providing a good base for nickel plating. The workpiece also needs to be washed with deionized water after secondary zincating.
Chemical nickel plating:
Put the workpiece that has undergone pre-treatment into the chemical nickel plating solution, with the solution formula being NiSO₄・6H₂O 25g/L, NaH₂PO₂・H₂O 30g/L, sodium acetate 20g/L, complexing agent A 30g/L, and trace stabilizers. Electroplate at a certain temperature for 60 minutes to form a uniform and dense nickel layer on the titanium alloy surface.