An Investigation on the Corrosion Protection of Mild Steel by Using the Conducting Polymer Polyaniline: Chemical and Electrochemical Studies

The interest for the preservation of the steel structure of ships and their prevention from corrosion in salted water is becoming more demanding with respect to the release of the toxic substances and their impacts on environment. Therefore, it is urgent to develop an adequate inhibitor to preserve the sea from the pollution. In this context, the study of the corrosion inhibition of a mild steel in seawater (i.e. 5% NaCl) by the polymer polyaniline (PANI) was carried out by using conventional techniques such as weight loss, electrochemical methods and scanning electron microscopy (SEM) coupled with the Energy Dispersive Spectrometry (EDX).The monitoring by cyclic voltammetry (i.e. current vs. voltage) allowed to see the influence of the scanning speed on the surface steel phenomena and showed also a linear evolution of the cathodic current density with the square root of the voltage scanning rate (i.e. I-p = f(V-1/2), where the diffusional type of charges transport was made in evidence. Whilst, the polarization curves using the sweep voltammetry in conjunction of the Tafel's processing, permitted to record the corrosion parameters. The electrochemical tests are thus, promising and have made it possible to highlight the effect of PANI cathodic corrosion inhibitor. The results obtained so far reveal a significant effectiveness against steel corrosion even at lower concentration (i.e. 0.3 g/L) where the inhibition rate was optimized to 93.28%. Besides, the SEM and EDX analyses allowed the clarification of the inhibition mechanism and support the relative inhibition efficiency.