Polydiallyldimethylammonium chloride, as well as acrylamide copolymers with trimethylammoniumethylacrylate, which are industrial flocculants, are tested as corrosion inhibitors on St45 steel. The inhibitor properties are manifested by polydiallyldimethylammonium chloride and acrylamide copolymer with trimethylammoniumethylacrylate chloride. These are determined by the adsorption of polymer molecules on the metal surface. The protective effect of inhibitors is estimated. A mechanism of the adsorption of the surface-active substances on an iron electrode surface is proposed.