Effect of Ratio of Isocyanate to Hydroxyl Functional Groups on the Anticorrosion Properties of Polyurethane Coating in Acidic Solution Using Electrochemical Impedance Spectroscopy

In this research, a two-component anti-corrosion coating based on polyurethane was made using polyacrylic resin and isocyanate hardener with different NCO/OH ratios. The anti-corrosion performance of these coatings was investigated using electrochemical impedance spectroscopy (EIS) with time in 1 M sulfuric acid. Equivalent circuit models were used to quantitatively compare the effect of the NCO/OH ratio on the anti-corrosion performance of polyurethane coatings. The results showed that with increasing the amount of hardener, the corrosion resistance of the coating first increases and then decreases and hence the best anti-corrosion performance of the coating was obtained at NCO/OH ratio of 1.2.