Chromium-free passivation method for surface of zinc coating

Abstract

The invention discloses a chromium-free passivation method for the surface of a zinc coating. The chromium-free passivation method comprises the following steps that (1) phytic acid, molybdate and a silane coupling agent with active groups containing carbon-carbon double bonds are mixed and stirred to be uniform, a solution A is obtained, polymer liquid of which a monomer at least contains two carbon-carbon double bonds and one hydroxyl group is prepared, polymer is prepared by addition polymerization of one of the carbon-carbon double bonds, a solution B is obtained, and graphene oxide dispersion liquid is prepared and serves as a solution C; (2) a zinc coating plated part is sequentially placed in the solutions A, B and C for a reaction to obtain a zinc coating plated part with a silanefilm-polymer-graphene oxide composite passivation layer on the surface; and (3) the plated part is placed in reducing atmosphere for the reaction to obtain the zinc coating plated part with the silanefilm-polymer-graphene composite passivation layer on the surface. The preparation process disclosed by the invention is simple and economical, the corrosion resistance time of the neutral salt mist of the prepared zinc coating plated part compounded with the passivation layer is about 700h, the adhesive force is the first grade, and the electrode potential can reach +1.4 V.

Description

technical field [0001] The invention relates to the technical field of metal anticorrosion, in particular to a chromium-free passivation method for the surface of a galvanized layer. Background technique [0002] Due to the strong activity of metal materials, galvanized parts are commonly used, which are easily oxidized by oxidizing gases or liquids in the environment during use. Therefore, researchers usually compound a protective layer on the metal surface. layer. The protective layer has a sacrificial anode cathodic protection method, such as plating a layer of metal material with better activity; another protection method is to combine a passivation layer with poorer activity, such as oxide layer, organic layer and organic-inorganic composite The most commonly used method is to use hexavalent chromium or trivalent chromium to oxidize the surface of the coating to form a dense protective film, but the chromium element used in this method will pollute the environment, so ...

AI Technical Summary

Problems solved by technology

The protective layer has a sacrificial anode cathodic protection method, such as plating a layer of metal material with better activity; another protection method is to combine a passivation layer with poorer activity, such as oxide layer, organic layer and organic-inorganic composite The most commonly used method is to use hexavalent chromium or trivalent chromium to oxidize the surface of the coating to form a dense protective film, but the chromium element used in this method will pollute the environment, so chromium-free passivation Fa is the future development trend

For example, CN201810669324.2 discloses the silane / graphene oxide composite passivation solution and its preparation method and application. This patent obtains a passivation layer by immersing metal materials in a mixture of silane coupling agent and graphene oxide, realizing organic and Inorganic composite passivation, but this method is one-time impregnation, the hydroxyl groups after hydrolysis of silane and the hydroxyl groups on the surface of graphene oxide may interact with the metal, the material on the surface of the passivation layer is uncertain, if the organic layer It is easily damaged when scratched, and the impermeability and wear resistance of graphene oxide cannot be fully exerted; at the same time, the pH of the passivation solution can reach 2, and the acidity is too strong. It will also etch the metal surface, resulting in The resulting passivation layer is not strong enough and uniform