Environment-friendly trivalent cobalt-free color passivation solution for zinc layer, and passivation process

Abstract

The invention discloses an environment-friendly trivalent chromium cobalt-free color passivation solution for a zinc layer and a process, and mainly relates to the technical field of metal surface treatment and protection. The raw material of the passivation solution is prepared from the following components in proportion: 50-500 g / L of trivalent chromium salt; 0.1-100 g / L of an auxiliary film forming agent; 10-200 g / L of a complexing agent; 10-150 g / L of an oxidizing agent; 10-100 g / L of a pH regulator; solvent is water. The present invention has no cobalt, low nitrate, and iron-resistant impurities and has excellent corrosion resistance, a passivation film is bright in color, and the passivation process is simple to operate.

Description

technical field [0001] The invention relates to the technical field of metal surface treatment and protection, in particular to an environment-friendly trivalent chromium-free cobalt-free colored passivation solution and a passivation process for zinc layers. Background technique [0002] With the development of industrial technology, higher and higher requirements are put forward for the corrosion resistance of the material surface. Due to its good corrosion resistance and price advantage, electrodeposited zinc is widely used in many fields such as daily hardware, automobiles, ships, electronics, and aerospace. Due to the active nature of zinc, it is easy to be corroded under hot and humid environmental conditions. If the electrodeposited zinc workpiece is not post-treated, the surface will be corroded quickly and produce white stains. After a long time, the substrate will continue to corrode the substrate (iron) Red rust occurs and the anti-corrosion effect is lost. In o...

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Problems solved by technology

Moreover, the existing passivation solutions generally have poor resistance to iron impurities. When the concentration of iron ions is above 50ppm, the passivation speed will be significantly accelerated, and macular spots will appear in severe cases, which has a great impact on the appearance.

For example, in the trivalent chromium color passivation technology mentioned in CN 201811379692, although cobalt salt is not used, and the amount of nitrate is relatively small, a lot of nitric acid is added, and the overall concentration of nitrate is very high; the environmental protection color passivation technology mentioned in CN201810604760 Passivating agent, wherein not only introduced nitric acid but also a large amount of phosphoric acid, has a greater impact on water bodies; heavy metal nickel and nitrate are used in CN201210327002, because the concentration of its film-forming agent and auxiliary film-forming agent is very low, the corrosion resistance is also low Relatively poor; using other oxidants such as hydrogen peroxide to replace nitrate is mainly used in the passivation of hexavalent chromium. The use of trivalent chromium in the passivation solution of trivalent chromium will oxidize trivalent chromium to hexavalent chromium, causing hexavalent chromium to exceed the standard, which is harmful surroundings

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