A study of H2S corrosion inhibition of pipeline steel by hydroxyethyl imidazoline has been carried out by using electrochemical techniques. Inhibitor concentration included 5, 10, 25, 50, and 100 ppm in a H2S-containing 3% NaCl solution at 50 degrees C. Techniques included linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), and electrochemical noise (EN) measurements. In addition to the traditional noise in voltage and current, noise resistance (R-n) measurements were used. All techniques showed that the most efficient inhibitor concentration was between 5 and 10 ppm, but inhibitor efficiency decreased after 8 h of testing. Furthermore, EN measurements showed that steel was highly susceptible to localized corrosion at inhibitor doses lower than 10 ppm due to the establishment of a porous inhibitor film. However, with 50 or 100 ppm of inhibitor, the steel was susceptible to a mixture of uniform and localized corrosion. Hurst exponent was higher in presence of inhibitor for times shorter than 8 h, indicating a short residence time of the inhibitor. The data could not be fitted to any adsorption isotherm model, indicating a lack of strong adsorption of the inhibitor to the metal surface.