For decades, the Bureau of Reclamation has used vinyl coatings for corrosion protection on gates. These structures are exposed to harsh environmental conditions with fluctuating water immersion and impact from debris. However, the vinyl systems are being phased out due to their high volatile organic compound (VOC) content. Prior laboratory research demonstrated that epoxy polysiloxane coatings may provide an alternative with initial results suggesting excellent corrosion protection in both atmospheric and water immersion environments despite manufacturers’ data sheets recommending the coating only as a topcoat for atmospheric environments, with no instructions for immersion service. This research tested the effect of cure time on electrochemical and physical properties for epoxy polysiloxanes applied to steel coupons. Specimens were sets and allowed them to cure for specified durations at 70 percent relative humidity and 21°C (70°F) before placed into laboratory immersion exposure and properties periodically measured using electrochemical impedance spectroscopy (EIS) and pull-off adhesion testing.

The results show that the polysiloxane provided adequate corrosion protection for all cure times. As the cure duration in 70 percent relative humidity increased, the initial barrier properties for the polysiloxane also increased. However, after 9 months of testing in immersion service, all test samples at different cure durations had the same barrier properties and adhesion testing results.