FUNCTIONALIZING THE BIOPOLYMER CHITOSAN FOR ON-DEMAND CORROSION INHIBITION IN CORROSION RESISTANT COATINGS

Chitosan is a linear polyamine that finds use in a range of industrial and medical applications due to its chemical functionality.  The compound is derived by deacetylation of the biopolymer chitin, which is a major component of the protective shells of marine crustaceans. The chemical functionality of chitosan is due to reactive amine and hydroxyl groups along the polymer backbone. We have exploited this functionality to make corrosion resistant coatings with self-healing properties and good adhesion. Under acidic conditions characteristic of coating application the amine sites on chitosan are protonated and receptive to anionic species such as vanadates, which are excellent corrosion inhibitors for high strength aluminum alloys. Under neutral or alkaline conditions, which are triggered by damage to organically coated metal surfaces, corrosion-inhibiting vanadates are released and act to stifle corrosion in damaged areas. Chitosan itself does not adhere well to aluminum surfaces, however additions of 3-glycidoxypropyl-trimethoxysilane to a chitosan coating formulation significantly improve chitosan adhesion by binding at hydroxyl sites on the chitosan backbone and at metal oxide sites on the surface receiving the coating. In this presentation, results from optical spectroscopy and electrochemical characterization are presented that show how the chemical functionality of chitosan can be exploited to create on-demand self-healing corrosion protection and enhanced adhesion in organic coating systems.