Aluminum alloy nickel plating pretreatment method

Abstract

The invention discloses an aluminum alloy nickel plating pretreatment method, which comprises cleaning, alkaline micro-etching and acidic neutralization: an acidic neutralization solution is a mixed solution of sulfuric acid and hydrogen peroxide; first zinc immersion: a zinc immersion solution is a mixed solution composed of zinc oxide, sodium hydroxide, lactic acid or/and malic acid and water; stripping: a stripping solution is a low-concentration HNO3 solution; second zinc immersion: the zinc immersion solution is the same as the zinc dipping solution used in the first time; and zinc reduction: a zinc reduction solution comprises glacial acetic acid, succinic acid, lactic acid and malic acid. According to the method, the pollution of zinc ions to a chemical nickel plating solution or anickel electroplating solution is greatly reduced, the service life of the chemical nickel plating solution or the nickel electroplating solution is prolonged, tank replacement of the chemical nickelplating solution or the nickel electroplating solution is reduced, and the binding force of the plating layer is kept at a high level. According to the method, the dosage of chemicals such as phosphate, zinc oxide and nitric acid can be greatly reduced, the waste liquid generated by the method is easier to treat, and the contained heavy metal zinc ions are easy to chemically settle and are separated from the waste liquid.

Description

technical field [0001] The invention relates to the technical field of aluminum alloy surface treatment, in particular to a pretreatment method before electroless nickel plating or nickel electroplating on aluminum alloys. Background technique [0002] Due to the self-passivation of the aluminum alloy, if the aluminum alloy is directly electroless nickel-plated or electro-nickel-plated, a coating with excellent adhesion cannot be obtained, and a special step of zinc-dipping treatment (zinc replacement) or nickel-immersion treatment is usually required. [0003] In the surface treatment industry, the pretreatment methods of electroless nickel plating or nickel plating on aluminum alloys are widely used as cleaning-alkali etching-neutralization-first zinc dip-nitric acid stripping-second zinc dip-electroless nickel plating or other electroplating. The cleaning agent used in the process usually contains phosphate, borate, sulfate, silicate and other inorganic salts and surfacta...

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Problems solved by technology

[0006] In particular, the strong complexing agent contained in the zinc immersion solution will cause difficulties in the chemical precipitation of heavy metal zinc ions in the wastewater, and it is difficult to use neutralization chemical sedimentation to treat the discharged wastewater to meet the standard (Table 3 in GB 21900-2008 The special discharge limit of water pollutants total zinc The requirement is less than 1mg / l), which makes the manufacturer very troubled

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