Method of coating the surface of a metal substrate

A method of coating the surface of a metal substrate, the method comprising:

• a) applying a first composition on the surface of a metal substrate, the first composition being in the form of a solution comprising a liquid medium including sol-gel precursors of alcoxysilane type or of metallo-organic type, said sol-gel precursors being suitable for bonding with the metal substrate, the sol-gel precursors applied during step a) having the same chemical nature;
• b) subjecting the first composition to a first heat treatment so as to form an anchor layer on the metal substrate in which the sol-gel precursors are bonded to the metal substrate, a first temperature being imposed during the first heat treatment that is sufficient to eliminate all or part of the liquid medium and to encourage the bonding of the sol-gel precursors to the metal substrate, the first heat treatment being configured to avoid complete condensation among the sol-gel precursors;
• and
• c) applying a second composition on the anchor layer, the second composition including coating compounds so as to obtain a coating on the anchor layer by forming bonds between the sol-gel precursors and the coating compounds.