Control of corrosion in stainless steel using polyelectrolytes multilayer nanofilms

Abstract

Stainless steel rods are coated by ultra thin polyelectrolyte multilayers. Multilayer systems are prepared using the method of layer-by-layer self assembly. This method involves alternating exposure of a charged substrate to solutions of positive and negative polyelectrolytes, respectively, with rinse step in between to remove any extra material that is loosely bound to the surface. Cationic polyallylamine hydrochloride (PAH) is used with anionic polystyrene sulfonate (PSS), polystyrene sulfonate-co-maleic acid (PSS-co-MA) and polyacrylic acid (PAA) in order to investigate the effect of changing the acidic strength of the anionic polyelectrolyte on the corrosion protection performance. Cationic polydiallyldimethylammonium chloride (PDADMAC) is used with anionic sulfonated polyetherether ketone (SPEEK) with three different ion exchange capacities to investigate the effect of changing the level of ionic charge of the polyelectrolytes on the corrosion properties. We investigated the corrosion properties of 316 stainless steel wires coated with PEMs of hydrophobically modified cationic PDADMAC and anionic PSS. The effect of hydrophobic modification of polyelectrolytes on the corrosion properties of the coated rods is investigated using poly(diallyldimethylammonium chloride-codiallyldodecylammonium chloride) (PDADMAC-co-DADDAC) and poly(diallyldimethylammonium chloride-co-diallyloctadecylammonium chloride) (PDADMAC-co-DAODAC). (PDADMAC-co-DADDAC) contained 3, 6 and 9.8 mole% of the hydrophobic comonomer diallyldodecylammonium chloride, while (PDADMAC-co-DAODAC) contained 3.6, 7.7, 10 and 15.6 mole% of diallyloctadecylammonium chloride. By applying different corrosion tests to the coated rods, the effects of hydrophobic modification of polyelectrolyte and other different parameters on the corrosion is investigated. The corrosion rates of the coated rods with different number of layers are always less than that of the uncoated samples.