A method for forming a coating film at part of a surface of a substrate includes, in sequence, a first step of applying a masking agent having inert particles over part of the substrate through a screen having blocked areas, a second step of depositing the coating film under at least partial vacuum over at least part of the surface covered and not covered by the masking agent, and a third step of removing the masking agent covered by the film with the aid of an aqueous fluid.