Cr-free dacromet coating prepared through mechanical alloying and preparation method thereof

Abstract

The invention belongs to the field of coatings and particularly relates to a Cr-free dacromet coating prepared through mechanical alloying and a preparation method thereof.The Cr-free dacromet coating is prepared from, by mass, 50-55% of metal alloy slurry, 40-45% of a Cr-free passivation solution and 3-6% of a related auxiliary agent.The metal alloy slurry is prepared from metal alloyed powder and a wetting agent through a ball milling technology.The metal alloyed powder is prepared from sheet zinc powder and sheet aluminum powder through ball milling mechanical alloying.The mass ratio of the zinc powder to the aluminum powder is (5:1)-(9:1).The total mass of the zinc powder and the aluminum powder is the same as the mass of the wetting agent.The obtained Cr-free dacromet coating is more stable in performance and low in porosity, few microscopic cracks and holes of the coating exist, the compactness of the coating is high, the corrosion resistance of the coating is good, and the environmental requirement is met on the premise that the performance requirement is met.

Description

technical field [0001] The invention belongs to the field of coatings, and in particular relates to a chromium-free dacromet coating prepared by mechanical alloying and a preparation method thereof. Background technique [0002] Dacromet coating, also known as zinc-chromium coating or zinc-aluminum coating, is a kind of anti-corrosion coating with simple process but excellent corrosion resistance. This technology comes from the western automobile industry. Dacromet technology is to apply the coating solution made of flake zinc powder, flake aluminum powder, chromic anhydride, wetting agent, dispersant, reducing agent, deionized water and other additives on the surface of steel and other substrates. Dry at about 330°C, and form a coating with excellent corrosion resistance on the surface of the metal substrate after curing and sintering. During the sintering process of Dacromet coating, chromic acid will undergo complex chemical reactions with the flake zinc-aluminum powder ...

AI Technical Summary

Problems solved by technology

The self-corrosion potentials of zinc and aluminum are -0.762V and -1.667V respectively. The zinc-aluminum coating formed by the combination of the two has a self-corrosion potential of about -1.1V, while the self-corrosion potential of general steel is 0.6 ~ -0.7V , in electrochemical protection, the more negative the potential of the coating, the more obvious the protective effect of the sacrificial anode, so when the workpiece is in a corrosive medium, the primary battery composed of coating and steel, the coating will act as an anode to lose electrons slowly Corrosion to protect the steel, but the Dacromet coating liquid prepared at present, flake zinc powder and aluminum powder are directly mixed in the form of simple substances in proportion to the preparation of the coating liquid, zinc powder and aluminum powder are not very good Combined as a whole, the corrosion potential of the coating is affected, which in turn affects the anti-corrosion ability of the coating

[0005] (2) The coating liquid is not uniform enough

The binder in the traditional Dacromet coating solution is chromic anhydride or chromate, and the Dacromet coating solution contains 2% to 5% Cr 6+ , even after high temperature sintering, there is still a small amount of soluble Cr 6+ stay in the coating, Cr 6+ It is highly toxic and carcinogenic, and has certain harm to the environment and human body. It is a dangerous environmental pollutant