Mechanism of CO2 Corrosion Inhibition by Phosphate Esters

Abstract

Abstract The mechanisms of corrosion inhibition of mild steel by phosphate esters in a CO2 containing environment is studied by using various inhibitor solution characterization techniques (residual analysis, dynamic surface tension, emulsion tendency). Corrosion inhibition and inhibitor film persistancy is monitored over time by using a rotating cylinder electrode (RCE) system and linear polarization resistance (LPR) technique. Corrosion rate-time/concentration profiles are obtained for all phosphate esters studied. Optical profilometry is used to assess surface microstructure as related to inhibitor film persistency. The effect of phosphate ester’s chemical structure (aromatic vs. aliphatic hydrophobic group, degree of ethoxylation, mono- vs. di-ester) on inhibitor performance is investigated in terms of their solubility, hydrolytic stability, emulsion properties, iron/calcium salt/complex formation and oil/water partitioning. A synergy between phosphate esters and imidazolines is also investigated.