Composition for metal surface treatment, metal surface treatment method, and metal material

摘要

Disclosed is a composition for metal surface treatment which enables to form a chemical conversion coating film which achieves sufficient foundation surface concealment, coating adhesion and corrosion resistance. Also disclosed are a metal surface treatment method, and a metal material. Specifically disclosed is a composition for metal surface treatment containing a zirconium compound and/or a titanium compound, and an organosiloxane which is a polycondensation product of an organosilane and has at least two amino groups in a molecule. The polycondensation rate of the organosiloxane represented by the mathematical formula (1) below is not less than 40%. The content of the zirconium compound and/or titanium compound in the metal surface treatment composition and the organosiloxane content in the metal surface treatment composition are at predetermined values, while the mass ratio of the zirconium element and/or titanium element contained in the zirconium compound and/or titanium compound relative to the silicon element contained in the organosiloxane is at a predetermined value. Polycondensation Rate % = Mass of Organosiloxane × 100/(Mass of unreacted Organosilane + Mass of Organosiloxane) (1)