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 persistency 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 fihn 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 volubility, hydrolytic stability,
emulsion properties, iron/calcium salt/complex formation and oil/water partitioning. A synergy between phosphate esters and irnidazolines is also investigated. Keywords: phosphate esters, residuals, ICP, rotating cylinder electrode, LPR, ethoxilation, hydrolysis, oilfield, CO2, imidazoline