A new environmental protection method for metal parts anti corrosion

The aim of this method is to develop an anticorrosive coating for metal workpieces that do not contain chromium and chromium-based derivatives, in particular hexavalent chromium, which can preferably be applied in a thin layer while providing high efficiency protection.

Suitable for work pieces with metallic properties (especially steel, cast iron) that require good corrosion resistance and thin layer.The geometries of the work pieces are of little importance as long as they remain suitable for applications using the method described.

This improves the corrosion resistance of coating formulations that do not use chromium, especially hexavalent chromium.

So far, many solutions have been proposed for chromium-based anticorrosion treatment.Although they are generally satisfactory in terms of the protection of metal workpieces, they have come under increasing criticism because of their consequences in terms of toxicity, particularly because of their harmful effects on the environment.

An anticorrosive coating for metallic workpieces relates to an anticorrosive coating for metallic workpieces characterized by a synergistic combination of a first layer based on metallic zinc and one or more coatings obtained using an aqueous composition containing granular metals, an appropriate solvent, a thickener and a binder composed of silane.

The first layer based on metal zinc can be prepared favourably by mechanical deposition.This coating consists of zinc or a coating consisting of zinc and ferroalloy, or a mixture of zinc and iron particles. DM2 coated metal can be applied in amounts from 50 to 300mg.For certain applications, even smaller deposits can be used.

A zinc-based layer is mechanically deposited by shot peening with the aid of a steel shot having at least one outer layer containing pure zinc or a zinc-based alloy.

This mechanical deposition based on metallic zinc coating can also be performed by shot peening by means of a mixture of steel shot and shot peening consisting of a steel core and having at least one outer layer based on A, zinc alloy or pure zinc coating on the surface.

Finally, such mechanical deposition based on metallic zinc coating can also be obtained by shot peening based on ferroalloy. Sandblasting is carried out in the presence of zinc powder or zinc particles and is therefore applied to the mechanical effect of blasting.