Al-Si alloy preplating bi-coordinating agent acidic zinc dipping solution and preparation method thereof

Abstract

The invention provides Al-Si alloy preplating bi-coordinating agent acidic zinc dipping solution and a preparation method thereof. The solution is characterized in that: the solution is prepared from 90 to 110g / L of zinc chloride, 10 to 30g / L of sodium citrate, 15 to 30g / L of ammonium bifluoride, 20 to 30g / L of boric acid, 15 to 20g / L of thiocarbamide, 1.5 to 2g / L of sodium dodecyl sulfate, 0.2 to 0.5 mL / L of 30 percent hydrogen peroxide, 1 to 3g / L of activated carbon and distilled water. The zinc chloride is taken as major salt, the sodium citrate and the ammonium bifluoride are taken as double coordinating agents, the boric acid is taken as a buffering agent and pH modifier, the thiocarbamide is taken as a hydrogen inhibitor, and the sodium dodecyl sulfate is taken as a wetting agent. Compared with other methods, the method of the invention has the advantages of simple process, easy control, low cost, little corrosion to a Al-Si alloy substrate, and quite good shape, evenness, density and coverage of zinc grains. The coordinating agents do not contain cyanides, which is beneficial to the environmental protection and the good health of operators, and can realize green production.

Description

technical field [0001] The invention relates to an acid zinc dipping solution for pretreatment of aluminum-silicon alloy plating, and also relates to a configuration method of acid zinc dip solution for pretreatment of aluminum silicon alloy plating. It belongs to the field of inorganic metal materials. Background technique [0002] Cast aluminum alloys, that is, aluminum alloys for castings and die castings, almost 90% are binary Al-Si alloys based on Al-Si and multi-element Al-Si systems containing a small amount of Cu, Mg, Ni and other elements. alloy. Aluminum-silicon alloy die castings, due to the specificity of their casting process and structure, make pretreatment before plating extremely difficult, and poor bonding is prone to occur after plating. There are many special pretreatment methods before aluminum-silicon alloy plating, such as galvanizing method, electroplating thin zinc layer method, anodic oxidation method, direct electroplating method, chemical nickel ...

AI Technical Summary

Problems solved by technology

However, due to the severe corrosion of the aluminum-silicon alloy matrix due to the alkaline zinc dipping solution, it cannot meet the precise requirements for the size of the parts, so the alkaline zinc dipping process has become increasingly unsuitable for aluminum-silicon alloys

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