High performance coatings: moisture cured urethanes

Abstract Polyurethane coatings are widely used for corrosion protection and colour stability as a topcoat for new construction and maintenance painting. When compared with other coatings, polyurethane systems rank among the lowest in life cycle costs. Polyurethane coatings also provide chemical and abrasion resistance, low temperature curing and the ability to be recoated. With the advance of technology, high performance moisture cured urethane (MCU) has evolved, offering durability, corrosion and chemical resistance, and colour and gloss retention. As the name suggests, the product cures in the presence of moisture. Moreover, MCUs have additional advantages such as no pot life being a single component system, fast curing, flexibility and surface tolerance. The resin is combined with various pigments to produce zinc rich primers, tar filled coatings, as well as coloured mid-coats and topcoats. Five different combinations of commercially available MCU coated panels were evaluated for their corrosion resistance and adhesion properties. Results were found to be satisfactory over 500 h of salt spray test (ASTM B117) and 168 h of water immersion tests (ASTM D870). Excellent results were obtained with respect to mechanical properties such as adhesion (ASTM D3359) and flexibility (ASTM D522).