Polyorganosiloxane (POS) grafted polysaccharide copolymers were synthesized through a heat-catalyzed dehydrating condensation reaction between the hydrolysates of potato starch (PS) as source of polysaccharide and N-[3-(triethoxysily)propyl]-4,5,-dihydroimidazole (TSPI) as the antimicrobial agent and source of the graft-forming POS at 200 degrees C in air. The grafting of POS onto PS followed by the opening of glycosidic rings significantly improved the thermal and hydrophobic characteristics of PS. The degree of wettability of Al surfaces by PS solution increased as the TSPI hydrolysate was incorporated into PS, thereby fabricating a thin uniform solid film over the Al substrate suitable for the protection of Al against corrosion. Consequently, the POS-grafted PS coatings derived from the precursor solution with a [PS]/[TSPI] ratio of 90/10 conferred an impedance of greater than 10(5) Ohm cm(2) and salt-spray resistance of 288 h.