Investigation of Mild Steel Corrosion in Hydrochloric Acid Solutions by Sodium carboxymethyl Cellulose and Polyethylene Glycol

Abstract

Investigation of mild steel (MS) submerged into 2 M HCl solution alongside sodium carboxymethyl cellulose (SCMC) and its mixtures with polyethylene glycol (PEG) and potassium iodide (KI) respectively was investigated by weight loss measurements, potentiodynamic polarization measurements and scanning electron microscopy (SEM). SCMC was not-good-enough at low concentration of 0.5 g/L of 2 M HCl solution at 30 °C as its inhibition efficiency (IE) stood at 42.73 and 40 % for 24 and 120 h immersion, respectively. However, increasing content of SCMC to 2 g/L of 2 M HCl solution at 30 °C, rose IE to 61.64 and 57.60 % at 24 and 120 h immersion, respectively. Effect of 0.5 g KI and PEG, respectively on 2 g SCMC/L of 2 M HCl solution at 30 °C for 24 h immersion improved IE to 70.91 and 83.64 %, respectively. Conversely, increasing temperature reduced IE of SCMC from 57.60 % at 30 °C to 46.30 % at 60 °C for 120 h immersion within 2 g/L of 2 M HCl solution; whereas 67.20 and 51.85 % at 30 and 60 °C as well as 69.60 and 55.56 % at 30 and 60 °C, respectively were obtained on adding 0.5 g KI as well as PEG, respectively to the 2 g/L SCMC. It was shown that SCMC-KI and SCMC-PEG mixtures show better IEs than SCMC alone, while the best IE of 83.64 % was found for SCMC-PEG mixture after 1 day of MS exposure to 2 M HCl solution. All inhibitor compounds were of mixed-type and obey Langmuir adsorption isotherm. Corrosion inhibition was afforded by physisorption of inhibitor compounds on the MS, while the good synergistic effect was owing to competitive adsorption of inhibitive combinations and thus enhanced inhibitor coverages on the MS. SEM gave visual evidence of adsorption by the compounds on MS. HIGHLIGHTS Steel corrosion is a primary concern in the oil and gas industry In this study, mild steel corrosion in hydrochloric acid solution was inhibited by sodium carboxymethyl cellulose. However, enhanced inhibitive performance was afforded by the combination of sodium carboxymethyl cellulose and polyethylene glycol Mechanism of inhibition action by sodium carboxymethyl cellulose and polyethylene glycol was highlighted Chemical and electrochemical approach to corrosion study was utilized GRAPHICAL ABSTRACT