Green Coatings for Industrial Applications R. Akid 1 *, H. Wang 1 , M. Gobara 2 , T.J. Smith 3 & J. Gittens 3 1 Materials and Engineering Research Institute, 3 Biomedical Research Centre,Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK. 2 Formally MERI, now at the Military Technical College, Cairo, Egypt. ( * corresponding author: r.akid@shu.ac.uk) Abstract: Despite their 150 year history, sol-gel coatings have made little impact on the industrial coatings scene largely because of their inorganic nature which has limited systems to the need for very high cure temperatures, ca. 500 o C +. Further issues such as; complicated processing, limited shelf life, lack of dry film thickness, restricted methods of applying the sol-gel coating system and poor adhesion to common engineering substrates have further limited the general application of this technology, being largely restricted to optical applications. This paper describes the recent development of environmentally-compliant ‘Green” sol-gel coating systems for industrial applications, examples being; a water-based chrome-free system for coil coatings, aerospace/transportation chrome-free pre-treatment/primer replacements and antifouling coatings. The sol-gel coating systems are based upon an inorganic-organic alkoxysilane precursors formulated to allow the incorporation of additives such as inhibitors, conducting polymers, nanoparticles and in the case of antifouling coating, an active non- pathogenic biological component. The performance of these coating systems has been assessed using standard industrial tests, electrochemical methods and field trials. 1. Introduction Sol-gel technology originates in the synthesis of inorganic gels, which has a long history dating back to 1846 by Ebelmen [1] who discussed the early developments with publications on the synthesis of silica gels from alkoxides. However, it was not until the 1970s that sol-gel technology began to gain industrial importance when monolithic inorganic gels were formed at low temperatures and converted to glasses without the need for a high temperature melting process. Conventional sol-gel materials are mostly oxides, in particular silica, alumina, aluminosilicates, titanium dioxide, zirconium dioxide and a long list of other oxide compositions. Since the 70’s, the synthetic technique of sol-gel processing has experienced tremendous development [2][3]. With the advent of "Hybrid organic–inorganic’’ systems, which are made of organic and inorganic components combined over length scales ranging from a few Angstroms to a few tens of