Reclamation Information Sharing Environment (RISE)

This report summarizes the results of a study expanding on S&T Project 1804, which investigated the effects of phosphating pretreatment on the adhesion of polyurethane coatings. An initial 2018 study indicated enhanced coating performance with a pretreatment of phosphoric acid and phosphoric acid derivatives. This study continues the investigation of the effects of phosphating, expanding the testing beyond adhesion to corrosion protection and simulations of field conditions. The study also includes an additional sample group using a moisture-cured urethane primer. Conclusions are drawn from the results of dry, wet, and knife adhesion testing; electrochemical impedance spectroscopy testing; rust creep measurements from four exposure tests; and hydraulic testing in high velocity water. Pretreatment with phosphoric acid, compared to pretreatment with its derivatives, as applied in this study, may improve coating performance. However, compared to phosphating pretreatments as applied in this study, using a moisture-cured urethane primer instead may further improve coating performance. Challenges with sample preparation and handling are discussed along with opportunities for future work.