Coated metal plate with excellent corrosion resistance and reduced environmental impact

Abstract

The present invention provides a chromate-free coated metal sheet excellent in corrosion resistance and coating material adhesion and having little affect on environment. The precoated metal sheet of the invention is a coated metal sheet comprising a metal sheet having on at least one surface thereof a film mainly comprising one or both of a metal oxide and a metal hydroxide each using a metal species exclusive of chromium, the precoated metal sheet having one or both of cracks in the film and pits on the underlying sheet and having an organic coat layer on the film.

Description

Technical field [0001] The present invention relates to a pre-coated metal sheet, and more specifically, it relates to having excellent paint adhesion and corrosion resistance, being environmentally friendly to the world due to the absence of hexavalent chromium (which is considered to have a significant impact on the environment) and suitable for use in Pre-coated metal sheets for automobiles, building materials and home appliances. Background technique [0002] In order to improve design performance and corrosion resistance, many metal plates used in home appliances, building materials and automobiles are pre-coated. For this kind of metal plate, in many cases, a chemical conversion treatment called chromate treatment is used as the pretreatment of the coating, because the chromate treatment provides the self-repairing function of the hexavalent chromium contained in the film. It has excellent corrosion resistance and provides excellent paint adhesion due to the hydrated oxide ...

AI Technical Summary

Problems solved by technology

This treatment agent does improve the paint adhesion to a certain extent, but the corrosion resistance is not necessarily satisfactory

[0007] As mentioned above, chromate-free treatments with high levels of paint adhesion and corrosion resistance have not been developed and are urgently needed