Patent ID: 8084123

Claim:
A process for preparing a stable sol-gel solution to be coated on a metallic substrate comprising, in succession, the following steps: a) preparing a sol-gel solution by bringing one or more molecular metal and/or metalloid precursors into contact with a medium comprising an organic solvent; b) adding at least one mercaptoorganosilane compound to the solution obtained in a); c) hydrolyzing the solution obtained in b); and d) adding to the solution obtained in c), one or more complexing agents chosen from: (i) carboxylic acids of formula R 1 —COOH, wherein R 1 represents a linear or branched alkyl group comprising from 1 to 30 carbon atoms, or a phenyl group; (ii) β-diketones of formula R 2 —COCH 2 CO—R 3 , wherein R 2 and R 3 independently represent a linear or branched alkyl group comprising from 1 to 30 carbon atoms, or a phenyl group; or (iii) hydroxamates of formula R 4 —CO—NHOH, wherein R 4 represents an alkyl group comprising from 1 to 30 carbon atoms, or a phenyl group, wherein the stable sol-gel solution is effective to coat the metallic substrate.