Preparation and characterization of anticorrosion polyurethane paints and coatings based on novel Zn-free phosphates

Novel aluminum ammonium phosphates (AAP) were tested as anticorrosion fillers in two-component solventborne polyurethane paints. Their properties were compared with microsized aluminum zinc phosphate (AZP) as well as with nanosized (nAP) and microsized (AP) aluminum phosphates. Generally, coating compositions containing AAP exhibited similar or slightly higher viscosity than the systems with AZP and AP. Moreover, cured polyurethane coats with AAP reached higher gloss and better adhesion to a steel substrate. The results of salt spray tests (2500 h) showed that anticorrosive properties of coats containing 10 wt% of AAP were similar or better than those noted for coats with 15.6 wt% of AZP or 13.7 wt% of AP. Electrochemical impedance spectroscopic tests revealed markedly higher barrier properties of coats with AAP in comparison to an AP-based sample.