A STUDY OF ACETIC ACID ROLE IN C02 CORROSION

The presence of organic acids typically acetic acid (HAc) in reservoir is known to
influence C02 corrosion. However, the mechanism of the higher concentration of HAc on
C02 corrosion is still unclear. The role of higher concentration of HAc in C02 corrosion
needs to be determined for accurate corrosivity prediction. The aim of the project is to
understand the role of different concentrations of HAc on C02 corrosion. The role of HAc in
C02 corrosion is investigated by using electrochemical impedance spectroscopy (EIS), linear
polarization resistance (LPR), scanning electron microscopy (SEM), and x-ray diffraction
(XRD) techniques. All experiments were conducted in a 3% NaCl solution of pH 5.5 and
temperature 60"C. In the absence of HAc, C02 corrosion produced iron carbonate film which
comes from the reaction of iron ions and carbonate ions. At 1000 ppm and 2000 ppm HAc, a
layer of iron acetate (FeAc) seems to form and solubilize continuously since the rate of
formation ofFeAc is much higher than that ofFeC03• By adding 4000 ppm of HAc, the FeAc
layer seems to grow due to the excessive amount of HAc and finally forming a layer on the
steel surface, thus reducing the corrosion rate. This behavior is shown by the EIS curves for
each concentrations of acetic acid. The formation of FeAc layer can be seen in the SEM
micrographs and the presence ofFeAc is confirmed by using the XRD technique.