Sol-gel-derived corrosion-protective coatings with controllable release of incorporated organic corrosion inhibitors

Sol-gel derived organo-silicate hybrid coatings preloaded with organic corrosion inhibitors have been developed in order to provide active corrosion protection when integrity of the coating is compromised. The incorporation of organic corrosion inhibitors into hybrid coatings has been achieved as a result of physical entrapment of the inhibitor within the coating material at the stage of film formation and cross-linking. Entrapped corrosion inhibitor becomes active in corrosive electrolyte and can slowly diffuse out of the host material. To ensure continuing delivery of the inhibitor to corrosion sites and long-term corrosion protection, a sustained release of the inhibitor is achieved by a reversible chemical equilibrium of either ion-exchange of the inhibitor with the coating material or through cyclodextrin-assisted molecular encapsulation. Several organic compounds, such as mercaptobenzothiazole, mercaptobenzimidazole, mercaptobenzimidazolesulfonate, and thiosalicylic acid, have been selected to evaluate the effectiveness of these two approaches. Corrosion protection performance of the coatings on aluminum alloy 2024-T3 has been examined using electrochemical methods including scanning vibrating electrode technique, potentiodynamic scan, and electrochemical impedance spectroscopy. (c) 2004 Elsevier B.V. All rights reserved.