POLYORGANOSILOXANE-GRAFTED POTATO STARCH COATINGS FOR PROTECTING ALUMINUM FROM CORROSION

Polyorganosiloxane (POS) grafted polysaccharide copolymers were synthe sized through a heat-catalyzed dehydrating condensation reaction betwe en the hydrolysates of potato starch (PS) as source of polysaccharide and N-[3-(triethoxysily)propyl]-4,5,-dihydroimidazole (TSPI) as the an timicrobial 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 glycos idic rings significantly improved the thermal and hydrophobic characte ristics of PS. The degree of wettability of Al surfaces by PS solution increased as the TSPI hydrolysate was incorporated into PS, thereby f abricating a thin uniform solid film over the Al substrate suitable fo r the protection of Al against corrosion. Consequently, the POS-grafte d PS coatings derived from the precursor solution with a [PS]/[TSPI] r atio of 90/10 conferred an impedance of greater than 10(5) Ohm cm(2) a nd salt-spray resistance of 288 h.