Galvanized chromium-free black passivating agent and preparation method thereof

Abstract

The invention relates to a galvanized chromium-free black passivating agent and a preparation method thereof. The galvanized chromium-free black passivating agent comprises the components such as nickelous chloride, molybdate, ammonium sulphate, a pH acid regulator, water and the like. The preparation method comprises the following steps of: operating the black passivating agent at the operation temperature of 20-40DEG C and the pH value of 4.0-5.0 for 0.5-1.5 minutes; preparing materials according to the mass fraction of various components; adding 50-70 percent of water in the raw materials into a stirring device; sequentially feeding other components; finally, adding residual water; and stirring for at least five minutes to obtain a finished product. The galvanized chromium-free black passivating agent has no hexavalent chrome and trivalent chromium, is suitable for black passivation of galvanized parts, can obtain a glossy black effect same as the passivation of the hexavalent chrome and the trivalent chromium and can meet the requirement of products. Before the galvanized chromium-free black passivating agent is dried, workpieces are not easily ground; and the passivated galvanized chromium-free black passivating agent is glossily black without being closed. The galvanized chromium-free black passivating agent has the advantages of strong corrosion resistance, no pollution, easiness in wastewater treatment and simpliness in operation.

Description

technical field [0001] The invention belongs to the field of post-processing of galvanizing, and in particular relates to a chromium-free black blunt agent for galvanizing and a preparation method thereof. Background technique [0002] Passivator is a chemical agent that forms a dense oxide film (passive film) on the metal surface under certain conditions to enhance the anti-corrosion ability of the metal. In the passivation of metals, the passivation of the galvanized layer occupies a special position due to its wide range, large quantity and strict requirements, and has attracted more and more attention from the industry and the whole society. At present, galvanized products at home and abroad still use chromate passivation. In recent years, this traditional use mode has been severely challenged and replaced by specialized production of passivators. Its composition and concentration are developing towards high quality, high stability and low toxicity, and substantial pro...

AI Technical Summary

Problems solved by technology

The common problems of the black passivation agents currently used in the market are that the cost is relatively high, and the stability of the passivation solution is difficult to control and difficult to adjust.

The chromium-free passivation solution provided by this invention can solve the problem of toxic and harmful hexavalent chromium and trivalent chromium elements contained in the existing product zinc coating and passivation solution, but the produced products cannot reach the level of chromium containing hexavalent chromium. The black ...

Images