Abstract: The invention relates to a process for preparing a stable sol-gel solution. The solution may be used to form coating materials for metallic substrates, such as silver-based substrates for use in mirrors. The process includes the steps of 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, adding at least one mercaptoorganosilane compound to the solution, hydrolyzing the solution obtained, and then adding one or more complexing agents to the solution.

Abstract: The invention relates to a process for preparing a stable sol-gel solution 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 carboxylic acids, ?-diketone compounds and hydroxamate compounds.