Preparation method of chromium-free passivating agent for cold-rolled sheet surface passivation

Abstract

The invention relates to the technical field of cold-rolled sheet passivation, and particularly relates to a preparation method of a chromium-free passivating agent for cold-rolled sheet surface passivation. The preparation method can meet the environmental protection requirements, improve the corrosion resistance of a passivated cold-rolled sheet, prolong the corrosion resistance time of the passivated cold-rolled sheet and meet the gradually rising requirements of users. The preparation method comprises the steps of (1) dissolving, specifically, adding 100g / L of magnesium fluoride, 20g / L ofammonium tripolyphosphate, 20g / L of sodium fluosilicate, 20g / L of a coordination agent, 4-5g / L of a catalyst, 25g / L of nitric acid, 35g / L of phosphoric acid and 12g / L of calcium nitrate into water anduniformly mixing; (2) adjusting the pH value, specifically, adding hydrochloric acid to adjust the pH value of the solution to 2.0; (3) adding silicon dioxide, specifically, adding silicon dioxide accounting for 40-50% of the mass of the solution into the solution after pH adjustment, and uniformly stirring to obtain a mixed solution; and (4) adding a surfactant, specifically, adding 2g / L of a surfactant into the mixed solution, and uniformly mixing to obtain the chromium-free passivating agent.

Description

technical field [0001] The invention relates to the technical field of passivation of cold-rolled sheets, in particular to a method for preparing a chromium-free passivator for surface passivation of cold-rolled sheets. Background technique [0002] As we all know, after the metal is treated with an oxidizing medium, its corrosion rate is significantly lower than that before the original treatment, which is called the passivation of the metal. The passivation treatment is the last process step in chemical cleaning, and it is a key step. Its purpose is to Corrosion protection of materials, such as after the boiler is pickled, washed with water, and rinsed, the metal surface is very clean, very activated, and easily corroded, so passivation treatment must be carried out immediately to form a protective film on the cleaned metal surface to slow down corrosion . [0003] The passivation mechanism can be mainly explained by the thin film theory, that is, the passivation is consi...

AI Technical Summary

Problems solved by technology

[0004] The passivator is the main component used for the passivation treatment of cold-rolled sheet, and its performance determines the corrosion resistance of the passivated cold-rolled sheet. , the use of chromate is strictly restricted, and low-toxicity chromate substitutes continue to be developed. The time for the first appearance of rust spots in the salt spray test of the rolled plate is relatively short, which does not meet the increasing needs of users