Synergistic Inhibition of Mild Steel Corrosion in Seawater and Acidic Medium by Cathodic Protection and Monodora myristica Using Zinc Anode

Abstract

The synergistic inhibition of mild steel corrosion in seawater and 0.1M sulphuric acid by the cathodic protection and Monodora myristica was carried out through the weight loss and the linear polarization resistance (LPR) measurement. The results showed that in seawater, the synergism was not too effective for the protection of steel, whereas in 0.1M sulphuric acid, there was a great synergism between cathodic protection and the oil extracts of Monodora myristica, having an efficiency (IE%) of 102.89% at 15 mL of the oil extracts. For the linear polarization resistance (LPR), in most of the cases, there was a slight shift of the corrosion potential (Ecorr) and the open circuit potential (OPC) toward the positive as the volume of the oil extracts increased, thereby causing a change in the cathodic and the anodic Tafel slopes, which showed that the inhibitor is a mixed- type inhibitor. The corrosion current density (icorr) decreases as the volumes of the oil extract increase. Langmuir adsorption isotherm fitted best with an R 2 of 1 unit, indicating a good agreement with the experimental data and with Langmuir adsorption isotherm.