Localized corrosion study of X60 pipeline steel in soil solution and inhibitive effect by disodic hydrogeno-phosphate

The used X60 pipelines steels for natural gas transmitting are susceptible to failures such as pitting corrosion or cracking in consequence of soil interaction with materials. The corrosion behaviour is simulated by means of electrochemical measurements such as potentiodynamiques polarization and electrochemical impedance spectroscopy (EIS) with and without the corrosion inhibitors containing polyphosphates ions. Appropriate models for corrosion parameters are used to fit the experimental data and extract the parameters that characterize the corrosion process. The corrosion rates were studied in different concentrations of corrosion inhibitors at different near neutral pH values. Results showed the bare steels sensitivity to corrosion and by increasing the temperature, the polarization resistance decreases and the corrosion speed increases as well as the densities of corrosion current I Corr . Corrosion inhibitors tests showed a variation in inhibition performance with varying concentration, temperature and immersion time. Langmuir model have been tested to describe the adsorption behaviour of inhibitor on the steel surface for the temperature range.