Non-cyanide zinc depositing agent for aluminum alloy and aluminum alloy zinc depositing method

Abstract

The invention relates to a non-cyanide zinc depositing agent for an aluminum alloy and an aluminum alloy zinc depositing method. The non-cyanide zinc depositing agent comprises 60 to 180g / L of LiOH, 20 to 50g / L of ZnSO4, 10 to 30g / L of NiSO4, 0.5 to 5.0g / L of CuSO4, 0.5 to 2.0g / L of FeCl3, 20 to 50g / L of sodium citrate, 10 to 30g / L of sodium lactate, 1.0 to 3.0g / L of sodium nitrate, 0.10 to 0.30g / L of ethylene thiourea, 0.02 to 0.06g / L of lauryl sodium sulfate and 0.01 to 0.03g / L of 2,2'- dipyridyl. The non-cyanide zinc depositing agent is used for the aluminum alloy secondary zinc depositing technology, formed zinc grains are small and uniform, an obtained zinc immersion layer is thinner and more compact, the base body covering performance is good, corrosion resistance is higher, combination force between a base body and a coating is greatly improved, and meanwhile, a zinc immersion solution is stable in character and long in service life.

Description

technical field [0001] The invention belongs to the technical field of pre-plating zinc precipitation for aluminum alloys, and in particular relates to a cyanide-free zinc precipitation agent for aluminum alloys, and also relates to a zinc precipitation method for aluminum alloys using the cyanide-free zinc precipitation agent. Background technique [0002] Aluminum and aluminum alloys are materials widely used in industrial production and people's lives. Electroplating aluminum or aluminum alloys can effectively improve its electrical conductivity, thermal conductivity, and weldability, and improve its surface wear resistance, corrosion resistance, protection, decoration, and optical properties. Methods. However, aluminum metal is relatively active and easy to form a natural oxide film, and its electrode potential is too negative. When immersed in the electroplating solution, it can undergo substitution reactions with various metal ions. Any plating solution except chromium...

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Problems solved by technology

However, the existing alkaline cyanide-free zincating agents are all developed from the basic zincate solution whose main component is NaOH. NaOH is a complexing agent for zinc ions, and its concentration is related to the compactness, uniformity and density of the zinc layer. The particle size is closely related; when the concentration of NaOH is low, the crystal grains of the precipitated zinc layer are coarse; in order to make the zinc ions in the solution stabilize the complex ion and obtain a finely crystallized zinc layer, there must be a sufficient amount of NaOH, but NaOH alkali Strong corrosion resistance, strong corrosion in aqueous solution, if its concentration is too high, the corrosion of zinc precipitation agent is too strong, the loss of the aluminum alloy matrix will be large, and the replacement reaction will be violent, which will affect the quality of the coating.

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