Nanoparticle Surface Modification for Advanced Corrosion Inhibiting Coatings

Abstract

In the last decade, surface engineering of inorganic nanoparticles has advanced to the point that it has become possible to fabricate and tune the functional properties of nanoparticles. The final properties of a nanocomposite are related to the nanoparticle itself (aspect ratio), the degree of dispersion, and the identity of the surface groups (surface density, oligomer length, etc.). Additionally, surface engineering can produce functional nanoparticles and by extension functional nanocomposites. At the most basic level, functional nanoparticles are surface engineered to both disperse into a host phase (e.g. a coating) and to carry a functional agent. Protective coatings are the most effective weapon in the battle to prevent corrosion, and soluble chromate additives have historically been used for corrosion protection for both steel and aluminum. Chromates released from pigments "heal" the corrosion sites thereby stopping corrosion. Unfortunately, chromates are toxic and OSHA regulations have reduced workplace Cr(VI) levels to 5 ppm. Nanoparticle additives with triggered release mechanisms have been developed as chromate replacements in protective coatings. Nanoparticle additives are attractive materials for corrosion protection because their high surface areas allow them to function as carriers for molecular corrosion inhibitors and their small particle sizes often generate novel chemistries not observed in bulk materials that permit the design of triggered release mechanisms.