Corrosion protection of the potassium silicate conversion coating

Electrochemical impedance spectroscopy (EIS) and Nuclear magnetic resonance (NMR) were used to investigate the corrosion mechanism of the potassium silicate conversion coating. NMR showed that the coating mainly consists of Q2, Q3 and Q4 structure and then changes to SiO2 after corrosion test. The Q2 structure in the coating is beneficial for the anticorrosion property of the coating. The impedance of the coating measured at 0.01 Hz reaches 2.8×106 ohm∙cm2 with a high curing temperature, meaning that the anti-corrosion property of the silicate conversion coating can be improved by a high curing temperature according to EIS analysis.