FILM FORMATION AND CO2 CORROSION IN THE PRESENCE OF ACETIC ACID
The role of acetic acid (HAc) on the protectiveness of iron carbonate (FeCO 3 ) films in CO 2 corrosion has been investigated using electrochemical, scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques. HAc has recently been recognized as a major factor in premature pipeline failure causing either generalized or localized corrosion. The main cause of concern is the undissociated (free) HAc which is found in oilfield brines. The pH value of the brine determines both the amount of free HAc and the supersaturation (SS). In order for a protective FeCO 3 film to form, the SS value is critical. A series of experiments was performed to test the effect of various amounts of free HAc on cylindrical X-65 steel coupons at different values of pH at stagnant (no rotation) conditions. A 3% sodium chloride (NaCl) salt solution by weight was used to simulate oilfield brine. All experiments were conducted at fixed pH, 80°C to accelerate film formation. In order to ascertain that a FeCO 3 film was indeed formed, a XRD scan was conducted on the film observed on the sample at the end of experiment and the matching of constituent element peaks confirmed a FeCO 3 film. HAc was found to have no effect on film formation and on the final corrosion rates of X-65 mild steel. The SEM pictures show no effect of HAc on film formation and protectiveness at a fixed pH. No evidence of localised corrosion (pitting) was observed on the specimens.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:film formation and co 2 corrosion in the presence of acetic acid
Date of Publication:01/01/2004