Sol–gel derived hybrid coatings as an environment friendly surface treatment for corrosion protection of metals and their alloys

• Published in: Journal of sol-gel science and technology 2012-10, Vol.64 (1), p.124-134
• Main Authors: Balgude, Dinesh, Sabnis, Anagha
• Format: Article
• Language: English
• Subjects: Abrasion resistant alloys; Abrasion resistant coatings; Additives; Ceramics; Chemical synthesis; Chemistry; Chemistry and Materials Science; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Composites; Corrosion; Corrosion environments; Corrosion prevention; Corrosion resistance; Corrosion resistant alloys; Covalent bonds; Curing; Environmental impact; Exact sciences and technology; General and physical chemistry; Glass; Health hazards; Hybrid systems; Impact resistance; Inorganic Chemistry; Materials Science; Nanotechnology; Natural Materials; Optical and Electronic Materials; Organic chemistry; Original Paper; Pigments; Polyurethane resins; Protective coatings; Schedules; Surface treatment; System effectiveness; Thermal resistance; Thermal stability
• ISSN: 0928-0707; 1573-4846
• DOI: 10.1007/s10971-012-2838-z

Sol–gel derived organic inorganic hybrid coatings are effective corrosion protective systems for metals. They offer an excellent adhesion to metal as well as to the subsequent coat via strong covalent bond and a three dimensional network of –Si–O–Si– linkages which helps to retard the penetration of corrosive medium through the coating. Unlike conventional surface protection methodology, silane based pre-treatment is an environment friendly technology with number of advantages like room temperature synthesis, chemical inertness, high oxidation and abrasion resistance, excellent thermal stability, very low health hazard etc. Further, the hybrid silane provides required flexibility and an increased compatibility with the subsequent coating in multicoat systems. The performance properties of hybrid systems depend on number of parameters like type of silane (mono or bis), degree of hydrolysis, type and dosage of inhibitive/barrier pigments (in case of pigmented system), application techniques, curing temperature and curing schedule, need to be optimized. A guideline formulation for maximum corrosion resistance with low environmental impact consist of a superprimer (a bis-silane with conventional resins, chrome free inhibitive pigments and additives) followed by epoxy or polyurethane top coat as per the exposure conditions.