Corrosion of steel structures in marine environments is a problem that has to be considered during both design and maintenance. Offshore operators are currently looking to extend the design life of offshore facilities, structures and components to improve the affordability, and to increase their availability in later years of operation. To reach the above objectives, many paint manufacturers have put in the effort to study long-term anticorrosion performance of different protective coatings in global offshore environments.
According to ISO 20340, a set of minimum requirements for protective coating systems in offshore environments has been specified. For a nonzinc-rich primer system, a minimum of three coats and a nominal dry film thickness of 350 µm are required for areas exposed to atmospheric category CX (offshore).1 One popular protective coating for offshore structures is the use of a high-solids, glass flake-reinforced epoxy coating to reduce gas and moisture vapor diffusion through coating films. One key requirement of such coatings is to provide a high film build of 400-800 µm per single coat. However, it is challenging to formulate a high-solids, high-build epoxy glass flake coating with good sag control throughout its pot-life. The rheological properties of high-build epoxy coatings tend to deteriorate drastically over a period of time upon addition of polyamine hardener thickened with conventional hydrophilic fumed silica. This may impose a problem in the on-site application, where a delay in spray application after mixing the epoxy base (Part A) and amine curing agent (Part B) may cause the coating to sag at the specified film thickness.