Polypropylene glycol: A novel corrosion inhibitor for × 60 pipeline steel in 15% HCl solution

Polypropylene glycol (PPG) was investigated as a corrosion inhibitor for typical × 60 pipeline steel in 15% HCl solution using weight loss, electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM), linear polarization resistance (LPR) and potentiodynamic polarization (PDP) techniques. Water contact angle measurements and scanning electron microscopy (SEM) were employed for surface morphology characterization. Results obtained show that polypropylene glycol acts as a good corrosion inhibitor for × 60 pipeline steel in the strong acid environment. Inhibition efficiency increased with an increase in PPG concentration and temperature up to 55°C but decreased as immersion time was prolonged. Optimum inhibition efficiency of 90.5% was obtained at 55°C with 1000 ppm PPG concentration from weight loss method. Potentiodynamic polarization studies revealed that PPG functions as a mixed-type inhibitor. The corrosion inhibition effect of PPG could be related to the adsorption of PPG molecules on the metal surface which follows Langmuir adsorption isotherm model and a protective film formation.