A laboratory study was conducted to examine the potential impact of replacing a three-coat paint system with proposed polysiloxane two-coat alternatives. All three systems use a zinc-rich epoxy primer. The three-coat system has an intermediate epoxy coat and an aliphatic polyurethane topcoat. The two-coat systems use polysiloxane chemistry based topcoats that are applied directly to the primer in one coat. One of the two-coat systems was from the same manufacturer as the three-coat system. All three coatings were applied by the same applicator under controlled and supervised conditions. Tests examined physical properties, adhesion and weathering characteristics.
Although there were some minor differences in the performance of the coating systems, the study indicates that replacement of the currently used three-coat system with the tested two-coat systems would not result in significant reduction in coating performance or expected service life. Tests examining extra demands made on coatings exposed to the cold environments of Canada showed a noticeable but similar reduction in the flexibility and impact resistance characteristics of all the coatings when tested at -30°C versus at room temperature and 0°C.