Abstract: Process for depositing by electrografting a strong adherent polymer coating onto an electrically conductive surface comprising the step of electrochemical grafting of an active monomer for forming a primer coating P onto the surface and having as general formula: X0 (meth)acrylate wherein X is either part of a preformed polymer or is an intermediate agent for polyaddition reaction or is an anchoring group for attachment of a molecule having at least one complementary reactive group. Such process allows formation of new primer by one-step electro-grafting of a macromonomer. Such process also allows further modification of an initial electrografted polymer to increase the coating thickness by the grafting-from technique. Such process also allows to graft onto the primer coating compounds like functional polymer, peptide, protein, oligonucleotide, dyes, drugs, anti-bacterian compounds.