Metal pretreated with an inorganic/organic composite coating with enhanced paint adhesion

A method of pretreating metal to improve paint adhesion, comprising the steps of:

• providing an alkaline solution including at least one of a dissolved silicate and a dissolved aluminate,
• rinsing a metal sheet with the alkaline solution,
• drying the sheet to form a relatively insoluble inorganic layer,
• providing an aqueous solution containing a hydrolyzed silane and a hydrolyzed crosslinking agent,
• rinsing the inorganically coated sheet with the aqueous solution, drying the silane treated sheet thereby forming a siloxane layer on the inorganic layer, and
• painting the inorganic/siloxane composite coating whereby the siloxane forms an adherent bond between the paint and the metal substrate.

A method of pretreating steel to improve paint adhesion, comprising the steps of:

• providing an alkaline solution including at least 0.005M of one of a dissolved silicate and a dissolved aluminate,
• rinsing a chromium alloyed steel sheet with the alkaline solution,
• drying the sheet to form a relatively insoluble inorganic layer,
• providing an aqueous solution containing at least 0.1 vol.-% of a hydrolyzed silane and at least 0.02 vol.-% of a hydrolyzed crosslinking agent,
• rinsing the inorganically coated sheet with the aqueous solution,
• drying the silane treated sheet thereby forming a siloxane layer, and painting the inorganic/siloxane composite coating whereby the siloxane forms an adherent bond between the paint and the steel substrate.