Synergistic inhibition effect of red tetrazolium and uracil on the corrosion of cold rolled steel in H3PO4 solution: Weight loss, electrochemical, and AFM approaches

The synergistic inhibition effect of red tetrazolium (RT) and uracil (Ur) on the corrosion of cold rolled steel (CRS) in 1.0-10.0 M H3PO4 solution was first studied by weight loss and potentiodynamic polarization methods. Atomic force microscope (AFM) provided the CRS surface conditions. The results revealed that RT had a moderate inhibitive effect, and the adsorption of RT obeyed the Freundlich adsorption isotherm. Polarization curves showed that RT was a mixed-type inhibitor in phosphoric acid. For the Ur, it had a poor inhibition effect, and acted as a cathodic inhibitor. However, incorporation of RT with Ur improved significantly the inhibition performance. The inhibition efficiency (IE) for RT in combination with Ur was higher than the summation of IE for single RT and single Ur, which was synergism in nature. Polarization studies showed that the RT/Ur mixture acted as a mixed-type inhibitor, which drastically inhibited both anodic and cathodic reactions. The synergistic inhibition effect of RT and Ur could also be evidenced by AFM images. Depending on the results, the synergism mechanism was discussed from the viewpoint of co-adsorption.