Corrosion Behaviors And Countermeasure Of Mild Steel In CO₂-Saturated Solution

Several oil tube steels were estimated and their anticorrosion properties were studied in Simulated Water from Deep Gaswell Containing CO. The order is that the first is 13Cr, then 3Cr and J55, and the last is P110．The corrosion rates of P110,J55 and 3Cr steels decreased gradually with increasing the test time, while the corrosion rate of 13Cr keep almost constant.Factors influencing corrosion rate of oil tube steels, such as Effects of temperature, pH value, CO₂ partial pressure and flow velocity on corrosion rate in carbon dioxide environment were studied by using weight-loss method, SEM and XRD. The results indicated that the temperature remarkably affects the characterization of corrosion product, and the corrosion rate rises along with the increasing of temperature up to 80℃,then reduces dramatically due to the formation of a protective layer on the surface of steel. Corrosion product was proved to be FeCO₃ in higher temperature. Corrosion will be aggravated by reducing pH value and increasing CO₂ partial pressure, the Cl^-concentrations and the flow velocity of solution. The common logarithm of the static corrosion rate of P110 increases linearly with common logarithm of CO₂ partial pressure, which agrees well with the results of De Waard, while the dynamic corrosion rate of N80 rises gently when the CO₂ partial pressure is more than 0．8MPa.In order to control the CO₂ corrosion and Couple Corrosion, the weight-loss method, the electrochemical method and atomic force microscope (AFM) were applied to study some imidazoline derivate inhibitors. Im-D and Im-Z which can efficiently retard CO₂ corrosion and Couple Corrosion respectively were synthesized and mixed in this paper. Their inhibition mechanism were always study.