Trivalent chromium pearl opal passivator for galvanizing and manufacturing method thereof

Abstract

The invention discloses a trivalent chromium pearl opal passivator for galvanizing, whose composition and mol ratio is : trivalent chromium salt: nitrate or nitric acid : fluoride being 1:1:0.25-1:10:1.25, trivalent chromium ion concentration in passivation liquid being 1-10g / L. The invention also discloses the passivator production method, i.e. adding each ingredient in stirrer and stirring, resolving material, then adding water, acid, adjusting passivator concentration liquid Cr#+[3+]ion concentration to 25-30g / l,pH 0.8-1. The inventive passivator not only has no production of hexavalent chrome pollution in production process, but does not contain hexavalent chrome itself, which comprehensively promote the product quality, appearing color uniformity, and more resistance to corrosion than Cr#+[6+].

Description

technical field [0001] The invention relates to a passivating agent for zinc plating, in particular to a trivalent chromium blue-white passivating agent for zinc plating, and also relates to a manufacturing method of the passivating agent. Background technique [0002] In order to improve the aesthetics and corrosion resistance of galvanized surfaces, Cr 6+ Chromate passivation treatment is carried out on it. In the past, in order to obtain a blue-white galvanized passivation film, Cr 6+ Rainbow passivation, which is then bleached with alkali. Later, a low-chromium one-time blue-white passivation process was invented, the content of hexavalent chromium in the passivation solution was reduced to 2-5g / L, and 0.2-0.5g / L of chromic anhydride was added in the final hot water scalding Improve the salt spray test time of the product (see "Electrogalvanizing and Zinc Alloy" Machinery Industry Press, written by Shen Pinhua and Tu Zhenmi). There are two deficiencies in the above bl...

AI Technical Summary

Problems solved by technology

There are two deficiencies in the above blue-white zinc passivation process: one is still to use Cr 6+ , and there are still 0.002~0.004mg / dm in the passivation film of the product 2 The second is that the blue and white zinc products made by these two processes can generally only reach 24 hours in the 5% neutral salt spray test [(NSS) GB-6458-86], while according to GB12335-90 "Specimen Rating after Corrosion Test of Anodic Covering Layer on Substrate", can only reach C7 level, and the corrosion resistance is not ideal

From the appearance, the blue and white zinc made by the old technology is more prone to yellow, especially some corners and places that have not been in contact with the air in time after passivation