Secondary zinc plating pretreatment composite solution for electroplating nickel on magnesium alloy surface

Abstract

The invention discloses a secondary zinc plating pretreatment composite solution for electroplating nickel on a magnesium alloy surface. The composite solution comprises a zinc immersion solution and a zinc electroplating solution, wherein the zinc immersion solution is composed of the following components: zinc sulfate with a concentration of 32-36 g / L, potassium pyrophosphate with a concentration of 200-210 g / L, sodium carbonate with a concentration of 8-10 g / L, potassium fluoride with a concentration of 3-5 g / L, ammonium bifluoride with a concentration of 2-3 g / L, and the balance being water; and the zinc electroplating solution is composed of the following components: ZnSO4.7H2O with a concentration of 32-36 g / L, KF with a concentration of 18-20 g / L, K4P2O7.3H2O with a concentration of 164-168 g / L, C6H17O7N3 with a concentration of 32-36 g / L, phytic acid with a concentration of 0.4-0.6 g / L, H2CSNH2 with a concentration of 4-6 g / L, and the balance being water.

Description

technical field [0001] The invention relates to the technical field of electroplating, in particular to a secondary galvanizing pretreatment combined solution for electroplating nickel on the surface of a magnesium alloy. Background technique [0002] As a lightweight engineering structural material, magnesium alloy has high specific strength, high specific stiffness and superior shock absorption performance, and has a wide range of applications in transportation, communication, aviation, aerospace and other fields. However, magnesium alloys have high chemical activity, low electrode potential, and loose oxide film on the surface, resulting in low protection performance, which restricts the application and development of magnesium alloys. This has aroused people's attention to the surface corrosion and protection of magnesium alloy parts, and a lot of research has been done on the surface of magnesium alloys, such as anodic oxidation, chemical conversion film, organic coatin...

AI Technical Summary

Problems solved by technology

However, the process is complicated, the repeatability is poor, cyanide is used, the plating solution is poisonous, pollutes the environment, the brightness of the coating and the stability of the plating solution need to be further improved

[0004] In order to overcome the shortcoming of complex process, researchers have developed a direct electroless nickel plating method, such as JP2003073843, which uses chromic anhydride to etch magnesium alloys, performs electroless nickel plating after fluoride activation, and adjusts the electroless nickel plating solution with ammonia water to make it appear Weakly alkaline, once obtained the chemical nickel plating layer with good bonding force and high corrosion resistance, Li Degao et al. used deflocculation → chemical degreasing → light emission → neutralization → activation → pre-treatment in the patent CN1699634A magnesium alloy electroplating method The galvanizing process has obtained a relatively good pre-galvanized layer, and the pre-galvanized solution is cyanide-free, non-toxic and harmless. In the patent CN1737205A, people such as Yang Sheng pickled the magnesium alloy with concentrated hydrofluoric acid (11%) Afterwards, directly electroplate aluminum to obtain a relatively good aluminum coating. Chinese patent CN1641075A has described in detail the surface or activation treatment methods and surface plating methods of magnesium and magnesium alloys. Although these processes are all separated from cyanide electroplating, the treatment before electroplating The process is mostly based on the improvement of the DOW process