Investigation Of Corrosion Behavior And Corrosion Inhibitor For Carbon Steel Under High-pressure CO₂ Environment

The corrosion behavior of 20# steel and the corrosion inhibition effect of corrosion inhibitor under the condition of high-pressure CO₂ containing crude oil were investigated by means of dynamic weight loss method, electrochemical test, the microscopic analysis methods, etc.The corrosion behavior of 20# steel under different circumstances?the pressure of carbon dioxide, temperature, time and oil content? were studied by means of dynamic weight loss method. Moreover, scanning electron microscopy was applied to investigate the corrosion morphologies. And the corrosion behavior of carbon steel changed obviously.With the increase of carbon dioxide pressure, the corrosion rate of carbon steel increased.The corrosion rate of metal increased with the increase of temperature. With the increase of time, the corrosion rate of carbon steel firstly decreased then reached stable states. With the increase of oil content in the medium, the corrosion condition of the sample decreased slightly.The corrosion inhibition effect of thioureido imidazoline corrosion inhibitor under different circumstances?the pressure of carbon dioxide, temperature? were studied in the corrosive medium containing crude oil. Under different environment conditions, it showed high inhibition efficiency when the concentration of imidazoline corrosion inhibitor was100 ppm. Moreover, under the condition of 2.5MPa CO₂ and 80?,the inhibition efficiency of imidazoline corrosion inhibitor was up to 98.5%. And it could spontaneously adsorb on the surface of carbon steel. Meanwhile, the thioureido amide intermediate was synthesized.And the concentration ratio of the thioureido amide intermediate and dodecyl dimethyl benzyl ammonium chloride was 3:1, the compound corrosion inhibitor reached excellent protective effect. And the inhibition efficiency was up to 98.6%. It also exhibited high protective effect under different conditions.Effects of crude oil on the inhibition behavior of corrosion inhibitor were illustratedby electrochemical test, dynamic weight loss test, contact angle measurement, the microscopic analysis methods, etc. The protective effect of thioureido imidazoline corrosion inhibitor and composite corrosion inhibitor for carbon steel were investigated in the corrosive medium containing carbon dioxide and crude oil. The results illustrated that the charge transfer resistance of carbon steel increased obviously when adding corrosion inhibitor into corrosive medium which contained crude oil. Meanwhile, the corrosion rate of the sample decreased rapidly. It is also found that wettability of carbon steel surface against water was reduced, the corrosion condition of the sample surface changed slightly.