Aluminium basis material surface treatment method

Abstract

PROBLEM TO BE SOLVED: To provide a pretreatment method which imparts a chromium-free chemical conversion coating adhesiveness to a paint film and corrosion resistance equivalent to or better than those of a chromating conversion coating containing hexavalent chromium ions, when an aluminum-based substrate is subjected to the chromium-free chemical conversion treatment as an alternative method for the chromate conversion treatment.SOLUTION: A surface treatment method for the aluminum-based substrate comprises the steps of: subjecting the aluminum-based substrate to a treatment process including the chemical conversion treatment; and then painting it. The method also includes treating the aluminum-based substrate with a strongly alkaline aqueous solution or electrolyzed alkaline water before the step prior to the painting step including the chemical conversion treatment to enhance a cleanliness degree of the surface of the aluminum-based substrate.

Description

technical field

[0001] The invention relates to a surface treatment method for an aluminum base material. Background technique

[0002] A film of aluminum oxide, dirt, oil, and the like adhere to the surface of the aluminum substrate, which hinders the adhesion of the coating film. Therefore, it is necessary to remove the above-mentioned film, oil, and the like by coating pretreatment before coating.

[0003] In addition, since the aluminum base material has insufficient corrosion resistance, if there is a scratch on the surface, filiform corrosion occurs and an oxide film is easily formed on the surface, so it is necessary to apply pre-coating treatment to the surface of the aluminum base material The chemical conversion treatment in it improves the corrosion resistance. Moreover, the adhesiveness of an aluminum base material and a coating film can be improved by this chemical conversion process.

[0004] As this chemical conversion treatment, a chromate treatment is usu...