Biodegradable polysaccharide grafted polyacrylamide inhibitor for corrosion in CO₂- saturated saline solution

A biodegradable polysaccharide-based inhibitor is grafted with polyacrylamide (PAM) for oilfields' sweet corrosion. The green properties of agar and PAM were incorporated to synthesize an agar-grafted-PAM (AGGPAM) inhibitor. Electrochemical tests of Tafel and AC impedance, were used to determine the corrosion rate of carbon steel (C-steel) and protection efficiency in CO₂-saturated 3.5 wt% NaCl solution. The surface morphology was characterized using FESEM coupled with EDX. Results demonstrated the promising performance of AGGPAM in improving steel resistivity, achieving 85% efficiency at 500 mg L^-1 and reducing the corrosion rate from 33 to 4.9 mils per year at 25 °C. The electrochemical tests classified AGGPAM as a mixed-type inhibitor, yet with a larger potential to inhibit the cathodic hydrogen evolution. Kinetics study at a temperature of 50 °C revealed a deteriorated AGGPAM inhibition attributed to electrolyte diffusion through the weakly adsorbed AGGPAM film. Nevertheless, the AGGPAM-inhibited solution exhibited a corrosion rate of 26.7 mils per year at 50 °C, which is still lower than that of blank at 25 °C. The steel resistance was diminished from 1436 to 355 Ω cm² at 50 °C. Implementing AGGPAM coating reduced the steel corrosion rate to 9.6 mils per year, achieving 71% efficiency. AGGPAM inhibitor toxicity was evaluated using ADMETlab, which predicted negligible hazardous impacts. Lastly, potentiostatic testing of steel with AGGPAM at an applied potential of 50 mV illustrated surface protection and decreased current over a prolonged time. Herein, the experimental investigation revealed the promising capabilities of AGGPAM as an efficient corrosion inhibitor in oilfields.