Application of Frumkin Isotherm for Carbon Steel Corrosion in Soil Media

Abstract

This study investigated carbon steel corrosion in three types of soil media (laterite, yellow soil and kaolin). The Frumkin isotherm was used to study the mechanism of the corrosion process. A good linear correlation (y = 3.4x + 3.3) in terms of soil concentration vs. surface coverage was obtained with the value of R2 = 0.996 for carbon steel corrosion in laterite solution at 30oC. A standard weight loss method was used to determine the degree of surface coverage. Investigation on corrosion rate was also carried out on the basis of immersion time and temperature effects. The results showed that yellow soil solution yielded the highest corrosion rate on carbon steel coupon for 5 consecutive days and at various temperatures (30 – 90oC). The thermodynamic properties in terms of heat of reaction and entropy were also investigated in this corrosion study. The results showed that carbon steel coupon was least corroded in the environment of kaolin solution as indicated by its highest endothermic value and lowest entropy. The study showed that the findings are consistent in relation to thermodynamic properties. This work is beneficial for the corrosion study of carbon steel in soil media corresponding to lifetime of buried pipelines and cost safety.