Sanding or sandblasting is done to remove the oxide film on the titanium alloy surface, followed by a cold water wash. The titanium alloy was deoiled. Wash hot and cold. Activation: Immerse titanium alloy into titanium alloy chemical milling waste liquid, the main components of waste liquid are hydrofluoric acid 20~50ml/L, nitric acid 50~80ml/L, sodium dodecyl benzene sulfonate 0.1~0.4g/L, potassium fluotitanate 20~100g/L, 5~10min, 20-30℃ for activation, and remove after completion. The concentration: hydrofluoric acid concentration of 30% ~ 40%, nitric acid concentration of 65% ~ 68%, said percentage are mass percentage. In the method of the invention, the original two-step method of acid etching and activation can be replaced by one step to complete the process, thus reducing the complexity of operation and process. The titanium alloy milling waste liquid is directly used as the activation liquid without additional configuration, and the waste liquid of the self-milling workshop can be directly used, thus saving the cost.
There are many researches on steel electroplating or electroless plating at home and abroad, and the research scope is relatively wide, involving the coating wear resistance, corrosion resistance, bath stability and so on. However, titanium alloy is different from steel, because titanium metal activity is large, it is quickly oxidized in the oxygen-containing medium, forming a layer of dense oxide film on the surface, the oxide film has high chemical stability, it is because of the existence of this layer of oxide film, hinder the matrix and metal coating close combination, thus affecting the coating binding force. At present, titanium alloy electroplating or electroless plating pretreatment is generally carried out acid etching and activation two-step treatment, the process is more complex, and the need to configure a large number of acid etching solution and activation solution.
Titanium alloy chemical milling waste liquid substance concentration: 30% ≤ hydrofluoric acid concentration ≤ 40%, 65% ≤ nitric acid concentration ≤ 68%, the percentage of the mass percentage. After taking out titanium alloy, wash it quickly in cold water (20-30℃ water) and transfer it to electroplating tank or electroless plating tank, so as to minimize the cold water washing and retention time of titanium alloy after activation treatment in the air to reduce the formation of oxide film.
