Steel mill continuous annealing galvanized sheet chromium-free compound passivator and preparation method thereof

Abstract

The invention discloses a steel mill continuous annealing galvanized sheet chromium-free compound passivator which comprises the following raw materials in percentage by weight: 5-20 percent by weight of a main film-forming agent, 0.1-5 percent by weight of a coupling agent, 0.1-0.5 percent by weight of inorganic complex film-forming agent, 0.1-4 percent by weight of silicate, 0.1-0.4 percent of an emulsifying agent, 0.1-0.2 percent of a dispersing agent, 0.1-0.4 percent of a corrosion inhibitor, 0.1-0.3 percent of a protective colloid, 0.1-1 percent of a nanometer sealing agent, 0.1-0.4 percent of phosphate and the balance of water. The steel mill continuous annealing galvanized sheet chromium-free compound passivator disclosed by the invention is uniform in appearance, stabilizes a liquid, has an expiration date of above 90 days, is nontoxic and environment-friendly, and accords with the ROHS (Restriction Of Hazardous Substances) requirement. The steel mill continuous annealing galvanized sheet chromium-free compound passivator is simple in preparation process; a passivated film is uniform in appearance and has certain glossness. A galvanized sheet passivated by using the passivator has the advantages that the corrosion resistance is remarkably improved, the neutral salt mist SST (Sea Surface Temperature) resistant time reaches above 72 hours, the white rust area is less than 5 percent, the blackening resistance delta E is less than 5, the yellowing resistance delta E is less than 3, the alkaline resistance delta E is less than 3, the interlamination resistance R is less than 3 omega / cm, and the conductivity is less than 1 m Omega.

Description

Technical field [0001] The invention relates to the technical field of metal surface passivation, in particular to a chromium-free composite passivation agent for galvanized sheets of steel mill continuous withdrawal lines and a preparation method thereof. Background technique [0002] Steel is the most widely used metal material in daily life, but the corrosion of steel has brought us huge losses. Galvanizing on the surface of the steel plate is a common method to improve the anti-corrosion ability of the steel plate. However, because the galvanized layer is easily corroded in the air, especially in a humid environment, white spots and dark objects are formed, which affects the appearance quality of the galvanized steel plate and the candle resistance of the coating. It must be purified after galvanizing to improve its corrosion resistance. Currently, chromate purification is commonly used. [0003] However, the hexavalent chromium contained in chromate is a carcinogen and has h...

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Problems solved by technology

[0007] The purpose of the present invention is to solve the pollution problem of chromium in the chromate passivation solution and the trivalent chromium passivation solution, and the salt spray test that exists after the existing chromium-free passivation solution passivates the galvanized sheet shows white rust in a short time , poor corrosion resistance and other issues