Synergistic mechanism of amidation on corrosion inhibition of laurate triethanolamine for HT300 gray cast iron in NaCl solution

Abstract

Sarcosine was inserted between fatty chain and carboxylic group of lauric acid to obtain lauroyl sarcosine, and the corrosion inhibition of lauroyl sarcosine triethanolamine (LSTEA) was significantly improved. The synergistic mechanism of amide group and lauric acid was investigated by comparing the corrosion behavior on the surface of HT300 gray cast iron in 330 mg/L NaCl solution. The results showed that both lauryl triethanolamine (LATEA) and LSTEA could prevent corrosion. At 298 K, when 1000 mg/L inhibitor was added, the inhibition rates are 71.93% and 83.89%, respectively. The morphology analysis also verified that LSTEA had better inhibition properties than LATEA. Comparing the adsorption parameters and Density Functional Theory (DFT) calculation results, it was found that LATEA and LSTEA could spontaneously adsorb on the surface of gray cast iron as monolayer to form a stable protective layer. However, the chelation of amide group and the electron absorption effect could make the electron density distributed at the polar end of the whole molecule, covering the active sites at the interface to the maximum extent, so that LSTEA has more excellent corrosion inhibition for gray cast iron.