STP866

    Electrochemical Methods for Evaluating Corrosion Inhibitors in Strong Acid Systems

    Published: Jan 1985


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    Abstract

    Electrochemical techniques have been evaluated for determining the performance of corrosion inhibitors in oil well acidizing solutions. Tests have been made with a variety of corrosion inhibitor blends in hydrochloric acid over a range of concentrations using carbon steel electrodes. Two different scan rates were evaluated. Longer term immersion tests were made with the same inhibitors to evaluate the degree of inhibition and development of pitting.

    Reverse scan polarization was found to produce anodic hysteresis loops similar to what is observed with passive alloys in chloride containing environments. A number of parameters from the reverse scan polarization hysteresis loop have been examined for correlation with pitting tendency. The return potential anodic corrosion rate appears to have merit for showing pitting tendency. The pitting tendency seems to be most severe when the inhibitor is at a relatively low concentration. The poor correlation seen between the 16-h mass loss corrosion rates and the electrochemical corrosion rate estimates is probably caused by inhibitor exhaustion in the mass loss results. Polarization scan rate effects also showed that inhibitor adsorption kinetics affected the anodic polarization parameters.

    Keywords:

    corrosion, acid treatment, inhibitors, potentiodynamic polarization, Tafel slope, polarization resistance, pitting potential, reverse scan polarization, corrosion potential, anodic hysteresis, mass loss corrosion rate, sign test


    Author Information:

    Dean, SW
    Chief engineer of materials and principal research chemist, Air Products and Chemicals, Inc., Allentown, PA

    Woodroof, RA
    Manager of chemical research, The Western Company of North America, Fort Worth, TX

    Nichols, J
    Chief engineer of materials and principal research chemist, Air Products and Chemicals, Inc., Allentown, PA


    Paper ID: STP33783S

    Committee/Subcommittee: G01.11

    DOI: 10.1520/STP33783S


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