Innovative Coating System for the Corrosion Prevention of Galvanized Steel - UTC

Develop an innovative, environmentally friendly and self-repairing coating system for preventing corrosion of galvanized steel.

Research has demonstrated that silicates/silanes could protect metals against different forms of corrosion either as a single film without topcoats or as a paint adhesion promoter and corrosion retardant under different topcoats but that silicate/silane sol-gel films alone cannot provide adequate barrier properties for corrosion due to the pores and cracks present in the film after the films dry. They also cannot provide active corrosion protection and cannot stop the development of corrosion processes once a defect occurs. Incorporation of nanoparticles in the hybrid sol-gel system enhances the corrosion protection properties but these nanocomposite hybrid films still cannot provide an effective long-term corrosion protection without a self-repairing effect. One way to improve the self-repair properties of the hybrid films is the addition of a corrosion inhibitor, which can suppress corrosion initiated at the coating defects. The inhibitors however, decrease the stability and consequently the barrier properties of the film and release of inhibitors from coatings is relatively fast and not controllable. To reduce environmental concerns, conventional chromate conversion coatings (CCCs) and other synthetic polymers in anti-corrosion coatings could be replaced with biodegradable natural polymers (e.g., polysaccharides) while maintaining a comparable level of corrosion resistance for the coatings. Integrating polysaccharides into silicate/silane polymers through chemical bonds will introduce biodegradability and minimize environmental impacts; may help improve the mechanical properties of coatings as flexible molecular chains and act to relax stresses induced by freeze-thaw cycles or mechanical damage. Polysaccharide structure may be used to form an electroactive polymer (EAP) which would allow charge to flow along the molecular chain and offer a mechanism for corrosion inhibition. A three-coat system consisting of a polysaccharide/silicate/silane film as a primer on galvanized steels to provide good adhesion to the substrate and biodegradability, an ordered nanoparticles coating with encapsulated corrosion inhibitors and repairing agent as the interlayer (providing enhanced corrosion protection properties), and a silicate/silane sol-gel film as the topcoat to offer transparency and scratch-resistant properties, will possess outstanding properties that could be tailored to a myriad of corrosion prevention and other applications.