Chromium-free composite passivator for hot-dip galvanized steel sheet and preparation and application methods of composite passivator

Abstract

The invention relates to a chromium-free composite passivator for a hot-dip galvanized steel sheet. The passivator is prepared from the following raw materials in percentage by weight: 2.20-2.30% of water-base resin, 2.60-2.65% of main salt compound, 0.10-0.15% of organic silane, 0.07-0.09% of sulfate, 0.11-0.13% of inorganic zircon salt, 0.09-0.12% of inorganic acid and the balance of water. A preparation method of the passivator comprises the following steps: firstly, dissolving the organic silane in water; stirring till the organic silane is fully dissolved and adding the main salt compound; after the main salt compound is dissolved, adding the inorganic acid to measure the pH value; then, adding the sulfate and the inorganic zircon salt in the stirring state; after the sulfate and the inorganic zircon salt are fully dissolved, adding the water-base resin; stirring till the water-base resin is fully dissolved; adjusting the pH value to 3-4 by virtue of ammonium water; and standing for later use. An application method of the passivator comprises the following steps: firstly, degreasing the hot-dip galvanized steel sheet by virtue of an alkaline degreaser during use; then, respectively washing by using tap water and deionized water; and after drying, coating the composite passivator on the surface of the hot-dip galvanized steel sheet. The passivator provided by the invention is free from chromium and non-toxic and harmless. The thickness of a passivation film can reach 8-1.0mg / m<2>, and the corrosion resistance is close to that of a hexavalent chromium passivating liquid.

Description

technical field [0001] The invention relates to metal surface treatment, in particular to a chromium-free composite passivator containing zirconium salt for anticorrosion treatment on the surface of hot-dip galvanized steel sheets and a method for preparing and using the chromium-free composite passivator. Background technique [0002] Steel is the most widely used metal material in daily life, but the corrosion of steel brings huge losses. Galvanizing on the metal surface is an effective means to improve the corrosion resistance of steel plates. Hot-dip galvanized steel sheets have been widely used in different fields such as building materials, aviation, automobiles, and home appliances, and are one of the fastest-growing steel varieties in my country in recent years. [0003] For hot-dip galvanized steel sheets, under natural corrosion conditions, the anodic coating of the galvanized layer can not only cut off the atmosphere, but also the galvanized layer itself is prefe...

AI Technical Summary

Problems solved by technology

The pH of the passivation solution is 6-9, and the passivation solution has good stability, but its corrosion resistance is not as good as that of chromate passivation, which cannot meet industrial requirements.

[0010] JP 10-219138A discloses a metal surface treatment agent consisting of an aqueous binder solution of inorganic fillers, silicates or colloidal silicon dioxide for galvanizing or topcoating ferrous substrates coated with zinc-rich paint , the disadvantage is that the zinc layer is often corroded and produces white rust.