Inhibitors are employed predominantly for corrosion control in closed systems, as a cost-efficiently alternative to the use of high corrosion-resistant materials. Due to the environmental requirements that are currently imposed on the development of cleaner inhibitors, vegetal tannins, a class of natural, non-toxic, biodegradable organic compounds that can be obtained at reduced cost has been proposed. This review relates recent uses of several vegetal tannins in corrosion protection, particularly as corrosion inhibitors of iron and steel in acidic and near neutral media. Several methods of inhibition efficiency evaluations along with their action mechanisms are discussed. The present review presents some important patents in the development of vegetal tannins in corrosion protection of iron and steel.
Keywords: Tannins, corrosion inhibition, inhibition mechanism, ferric-tannates, lepidocrocite