Journal of Sol-Gel Science and Technology 32, 143–147, 2004 c  2004 Kluwer Academic Publishers. Manufactured in The United States. Sol–Gel-Derived Corrosion-Protection Coatings BAKUL C. DAVE ∗ , XIANKUI HU AND YOGEESWARI DEVARAJ Department of Chemistry and Biochemistry, Southern Illinois University, Carbondale, IL 62901, USA dave@chem.siu.edu SHIRSHAK K. DHALI Department of Electrical and Computer Engineering, Southern Illinois University, Carbondale, IL 62901, USA Abstract. There is a current need for alternative coatings that can provide corrosion resistance to metals or alloy surfaces due to the environmental hazards posed by conventional coatings. Herein, we report on novel organically- modified sol–gel coatings for the protection of metal and alloy surfaces. The basic concept of chemical conversion of metal surfaces is based on deposition of a hydrophobic, nonporous sol–gel barrier layer for surface protection and corrosion prevention. The properties of these organosilica coatings can be tuned by varying the composition of precursors. The evaluation of hydrophobicity, adhesive strength, and anticorrosion properties of organically-modified sol–gel derived coatings suggests their potential utility as technologically-compatible alternatives to conventional coatings. Keywords: organosilica sol–gels, barrier layer coatings, corrosion-protection, adhesion, hydrophobicity 1. Introduction Sol–gel-derived coatings have been found to be use- ful for several applications mainly due to the ease of solution based processing and the synthesis flexibility which can be used for forming a wide range of thin films and coatings [1, 2]. Using the sol–gel process, it is possible to deposit films and coatings with variable thickness from 100 ˚ A to several μm. In addition, the use of organically-modified precursors provides unique opportunities to tailor the physical and chemical prop- erties of the final materials. Due to the presence of an organic component, the organosilica coatings dry evenly and are more uniform and crack-free as com- pared to pure silica coatings. While there has been sig- nificant research activity in the use of sol–gel coatings for corrosion protection [3–5], efficient coating formu- lations that provide significant protection as a viable alternative to conventional coatings as yet remain to be realized. One of the critical issues with sol–gel-derived ∗ To whom all correspondence should be addressed. coatings has been their poor adhesion to the metal sur- face due to weak noncovalent binding to the substrate. An additional concern is their porous nature, which makes them permeable to ions, moisture, and other corrosive species. In this context, organosilica sol–gel materials furnish unique advantages [6]. The properties of sol–gel-derived coatings can be engineered at the molecular level [7] for optimum physical and chemical properties such as better adhesion, improved hydropho- bicity, low permeability, as well as texture, morphol- ogy, optical properties, and other characteristics. These materials can also be easily processed in the form of a coating using inexpensive, environmentally-friendly, and technologically-compatible methods. Herein, we report the use of organosilica sol–gel materials for coating metallic substrates. Different organosilicate precursors were used to prepare non- porous hydrophobic coatings which not only provide improved adhesion but also act as a barrier protec- tion layer for minimizing the permeability of corrosive species. It is found that the coatings are effective at preventing corrosion of metal substrates. The coatings