No abstract

Adjustments of the curing temperature and silica content were used to improve the corrosion protection properties of an organic−inorganic hybrid (OIH) coating based on a polyurethane-silica (SPU) system. Fourier transform infrared and nuclear magnetic resonance ( 13 C and 29 Si NMR) spectroscopy analyses revealed the conversion of urethane groups to secondary amines, with concomitant condensation of Si−R to Si−O−Si, when the curing temperature was increased, while small-angle Xray scattering analysis showed the formation of denser and less branched aggregates of the inorganic framework. The silica content influenced the roughness and thickness of the coatings, with values in the ranges 1.6−9.6 nm and 1.7−6.5 μm, respectively. All the hybrid coatings deposited on steel presented impedance modulus at the lowest frequency (|Z 5 |) above 0.1 GΩ cm 2 throughout the 28 days of analysis. The SPU coating prepared using a TEOS/ APTES ratio of 1 and a curing temperature of 167 °C presented the best performance as a corrosion protection barrier, characterized by predominant capacitive behavior and the invariance of |Z 5 | over 10 GΩ cm 2 .