TITLE:
Inhibiting Effect of Dioctyl Phthalate on the Corrosion of Mild Steel in 1.0 M Hydrochloric Acid Solution
AUTHORS:
Michael Emmanuel, Bethrand T. Nwufo, Mbanefo M. Ekwenchi
KEYWORDS:
Mild Steel, Dioctyl Phthalate, Weight Loss, Corrosion Inhibition
JOURNAL NAME:
Open Access Library Journal,
Vol.5 No.10,
October
31,
2018
ABSTRACT: Steel corrosion is a major and costly problem to industrialists and construction workers. The inhibiting effect of dioctyl phthalate on the corrosion of mild steel was carried out in 1.0 M solution of HCl as the corrosion medium using the weight loss method. The adsorption of the dioctyl phthalate on the surface of the mild steel in 1.0 M HCl was found to follow the physisorption mechanism and also follow the first order rate law. The corrosion rate was found to be di-rectly proportional to the temperature of the medium, and inversely proportional to the concentration of the inhibitor in solution. The activation energy increases with increase in the concentration of the inhibitor. Values of standard free energy change, are consistently below ﹣20 kJmol﹣1. This solidly established that the adsorption mechanism of the dioctyl phthalate on mild steel surface is physisorption. Langmuir and Freundlich adsorption isotherms were used, with Freundlich isotherm as best fit for the modelling of the adsorption process. The value nF in Freundlich isotherm which, indicates the intensity of adsorption, was found to be in the average of 0.717 not far from the typical value of 0.6 nF.