Abstract
Modern engineering science and nanotechnology have hastened the development of high performance corrosion-resistant coatings having a broad spectrum of effectivity under a wider range of hostile environments. The formulation of such coating systems is expected to cause a major revolution in the corrosion world. Conducting polymers have recently proved to be an effective alternative to phosphate-chromate pretreatment that is hazardous due to toxic hexavalent chromium. Moreover, improvements in environmental impact can be achieved by utilizing nanostructured particulates in coating and eliminating the requirement of toxic solvents. The paper reports some preliminary investigations on the corrosion resistance performance of nanostructured methyl orange (MO)-doped polyaniline (PANI)/castor oil polyurethane (COPU) composite coatings on mild steel (MS). The nanostructure of the MO-PANI was confirmed by transmission electron microscopy (TEM). The corrosion protective performance was evaluated by physico-mechanical properties, corrosion rate, and open circuit potential measurements. These coatings were found to act as "corrosion sensors" by exhibiting different colors when placed in acid as well as alkaline media. The protective behavior of coatings was attributed to the formation of a passive iron oxide/dopant layer at the metal-coating interface that impedes the penetration of the corrosive ions. Copyright (C) 2008 John Wiley & Sons, Ltd.