Aluminum alloy nickel pre-plating solution

Abstract

The invention provides an aluminum alloy nickel pre-plating solution. A weak acidic nickel plating solution containing organic acid is used as a pre-plating solution after the aluminum alloy zinc dipping treatment; the solution is prepared from main salt, conductive salt, a pH buffer agent, a complexing agents and organic acid; the main salt uses nickel sulfate with a mass concentration of 120-140g / L; the conductive salt uses sodium sulfate with a mass concentration of 15 to 30g / L; the pH buffer agent uses boric acid being 30 to 40g / L; the complexing agent uses Cit-3Na being 80 to 100g / L; theproportioning ratio of the complexing agent to the main salt is (0.67 to 0.71):1; the pH value of the solution is regulated to 3 to 4, the weak acidic state, by the organic acid. Compared with otherelectric plating pre-plating solution, the aluminum alloy nickel pre-plating solution does not have the toxicity; the ingredient content can be regulated to be stable for a long time; the processing cost is low; in addition, the solution is in a weak acidic state, so that the surface activity of the part can be maintained under the power failure condition; meanwhile, chloride ion ingredients are not contained; corrosion cannot be caused to the part base bodies; the potential differences of the nickel ion potential and the zinc dipping potential are similar, so that the part can enter a tank according to general operation; the occurrence of replacement reaction cannot occur.

Description

technical field [0001] The invention belongs to the technical field of surface treatment of aluminum and aluminum alloy parts, in particular to an aluminum alloy pre-plating nickel solution. Background technique [0002] Because the potential of aluminum and aluminum alloy is relatively negative, it is easy to contact with oxygen to form a thin and dense oxide layer during the surface pretreatment process, which is not suitable for direct electroplating processing. It is necessary to remove the oxide film on the surface, then galvanize and then electroplate a transition layer before other electroplating treatments can be done. [0003] For the electroplating of aluminum and aluminum alloy parts, there are two main methods widely used at home and abroad: 1. Secondary zinc immersion → weak alkaline cyanide copper plating → electroplating other coatings; 2. Secondary zinc immersion → pre-plating Nickel → electroplating other plating. [0004] Using the first pretreatment meth...

AI Technical Summary

Problems solved by technology

[0006] There are relatively few manufacturers using neutral pre-nickel solution for aluminum alloy production. The main reasons are: 1. The pH of the neutral pre-nickel solution is neutral or near-neutral, and nickel ions are prone to hydrolysis after the solution is energized. Ni(OH)2 precipitation is generated, and the deposited metal surface coating is porous and white spots, and the solution is not easy to clarify after being treated with a strong acid solution, and the adjustment is difficult; 2. The complexing agent citrate and the main salt in the neutral nickel plating solution The complexation ratio exceeds 1:1, which increases the precipitation potential of nickel ions in the solution, but also increases the working temperature of the solution

The internal stress of the nickel coating after electroplating is relatively large, and the brittleness of the coating is also relatively large. The parts are not suitable for working at higher temperatures, and fracture and bubbling are easy to occur

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