Inhibition of Under-Deposit Corrosion of Carbon Steel by Thiobenzamide

The inhibition performance of thiobenzamide (TB) against the under-deposit corrosion of carbon steel in CO2-saturated, chloride-containing environment has been investigated. TB concentrations were varied from 10 - 200 ppm and temperatures from 30 degrees C to 60 degrees C were tested. TB effectively inhibits corrosion at carbon steel surfaces with and without sand deposits, reducing the general corrosion rates below 0.1 mm y(-1) in all cases studied. Electrochemical test results suggest that inhibition occurs via adsorption at the steel surface through the S atom of the TB molecule. Potentiodynamic polarization measurements show that the inhibition mechanism differs at surfaces with and without sand deposits with temperature change over the range of 30 degrees C to 60 degrees C. Surface analysis of the corroded steels showed that general corrosion takes place at surfaces without sand deposits, whereas localized corrosion proceeds at the surfaces underneath a sand deposit, both in the presence and absence of thiobenzamide. (C) 2013 The Electrochemical Society. All rights reserved.