Corrosion Inhibition of Thiourea with Synergistic Effect of Potassium Iodide on Mild Steel in Brackish Water and Effluent Water

Abstract

The corrosion inhibition of mild steel in oilfield brackish water and effluent water has been studied in relation to the concentration of the thiourea (as corrosion inhibitor) as well as the temperature using weight loss method. The mild steel corrosion coupons were processed and evaluated as per international standard procedures i.e. NACE SP-0775 2013 and ASTM G1–03.

The corrosion inhibition efficiency was calculated using the equation:

Inhibition Efficiency (I%)=(W_O-W)/W_O X 100

Where W0 is the weight loss in the absence of inhibitor in solution and W is the weight loss in the presence of inhibitor in the solution.

The results were supplemented with scanning electron microscopy (SEM) and infra-red (IR) spectroscopy. The presence of C=S group, which enhances the electron density on the molecule, and act as the active sites for corrosion inhibitor adsorption leading to stronger bond with metal surface through physio-chemical adsorption by the formation of a protective barrier film. Synergetic effect of potassium iodide in corrosive media has been found to stabilize the adsorption, leading to improved inhibition efficiency. The results showed that Thiourea is a good corrosion inhibitor.

Keywords: Thiourea, Corrosion Inhibitors, Mild Steel, Adsorption Process, Scanning Electron Microscope (SEM), Infrared Spectroscopy (IR) Spectra

JEL Classification: Y40