Passivation solution capable of inhibiting formation of hexavalent chromium in trivalent chromium passivation layer as well as preparation method and application of passivation solution

Abstract

The invention discloses a passivation solution capable of inhibiting formation of hexavalent chromium in a trivalent chromium passivation layer as well as a preparation method of the passivation solution. Every liter of the passivation solution capable of inhibiting formation of hexavalent chromium in the trivalent chromium passivation layer comprises 15-25g of chromium sulphate, 1.5-3.0g of sodium nitrate, 4.0-9.0g of cobaltous sulphate heptahydrate, 2.5-5.0g of sodium hypophosphite, 0.4-1.0g of citric acid, 0.15-0.25g of ammonium hydrogen fluoride, 0.8-1.25g of D-sodium gluconate, 0.4-1.0g of acetic acid and the balance of deionized water. The preparation method of the passivation solution capable of inhibiting formation of hexavalent chromium in the trivalent chromium passivation layer comprises the following steps of: firstly sequentially adding sodium hypophosphite, citric acid, sodium nitrate and cobaltous sulphate heptahydrate into a chromium sulphate aqueous solution and dissolving, then sequentially adding ammonium hydrogen fluoride and D-sodium gluconate, and finally dropwise adding acetic acid, and adding water to maintain constant volume, thus the passivation solution capable of inhibiting formation of hexavalent chromium in the trivalent chromium passivation layer is obtained. The passivation solution can improve stability and tightness of a passivation layer and inhibit formation of hexavalent chromium.

Description

technical field [0001] The invention relates to a metal passivation solution, in particular to a passivation solution for inhibiting the formation of hexavalent chromium in a trivalent chromium passivation layer, a preparation method and an application. Background technique [0002] After the banning of the hexavalent chromium salt as the best passivation treatment for galvanizing, to find a suitable substitute for hexavalent chromium, people conducted research on chromium-free passivation to find suitable new material elements for metal passivation. However, molybdate, titanate, tungstate, rare earth, silicate, etc. used in chromium-free passivation are used as new corrosion-resistant materials, which are not ideal in appearance and corrosion resistance. However, there are still some limitations in production and application. In the absence of major breakthroughs in the development of new chromium-free passivators at home and abroad, manufacturers generally use trivalent c...

AI Technical Summary

Problems solved by technology

[0003] However, in recent years, in the electronic products exported by my country, it has been detected that the trivalent chromium passivation layer of some metal products passivated by the trivalent chromium passivation solution contains toxic hexavalent chromium, so they are banned from entering the country. Some cases have brought certain impact on my country's export market

It also shows that the trivalent chromium passivation layer obtained after the passivation of the trivalent chromium passivation solution does not exist stably, and the trivalent chromium in it can be converted into hexavalent chromium, which affects the stability of the trivalent chromium passivation solution. Requirements present new challenges

Images