ASSESSMENT OF ASPARTAME AS A GREEN AND EFFECTIVE CORROSION INHIBITOR FOR T95 CARBON STEEL IN STRONG HCl SOLUTIONS

Oil well acidizing, although a stimulation process, induce the corrosion of metallic equipment and well tubings. It is a necessity to use an effective corrosion inhibitor during oil well acidizing. However, current acidizing inhibitors, although effective are toxic to the natural environment and in some cases, very expensive. There is therefore, at present a high demand of effective, low-cost, and less toxic corrosion inhibitor for acidizing process. This work was thus designed to formulate a green and low-cost inhibitor formulation based on Aspartame (ASP) that can compete favourably with the commercially available acidizing corrosion inhibitors. The inhibitive effect of ASP for T95 CS in 15 and 28 wt.% HCl solution at 60, 70, 80, and 90oC was investigated using the weight loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), scanning electron microscope (SEM), energy dispersive spectroscopy (EDX), and optical profilometry (OP) techniques. Results from the weight loss and the electrochemical techiniques show that the retardation efficacy of ASP enhances with increase in concentration and temperature. At 90oC and 2000 ppm of ASP, inhibition efficiency of 85% and 88% is obtained in 15 wt.% and 28 wt.% HCl solution, respectively. Following the variation of inhibition efficiency of ASP with temperature, chemisorption mechanism is proposed for the adsorption of ASP onto the T95 CS surface in both 15 wt% and 28 wt.% HCl solution. In order to enhance the inhibitive performance of ASP, studies were undertaken to ascertain whether or not there is synergistic effect between ASP, potassium iodide (KI), and sodium dodecylsulfate (SDS). Results from weight loss studies reveal that synergistic effect existed between ASP, KI, and SDS especially at 90oC. Based on the synergistic studies, ASP-based cocktail was formulated in a ratio of 2 (ASP): 0.1 (KI): 0.1 (SDS). The formulation performed outstandingly at the studied corrosive media. At 90oC, 2000 ppm of the formulation exhibits inhibition efficiency of 92% and 96% in 15 wt% and 28 wt.% HCl solution, respectively from EIS technique. A comparison of the performance of the formulation with that of a commercially available acidizing inhibitor reveals that, the formulation perform better than the commercial inhibitor in 28 wt.% HCl solution but compete considerably in 15 wt% solution. The PDP results reveal that ASP alone and in combination with additives acted as a mixed-type corrosion inhibitor in the studied environment and inhibited both the anodic oxidation and cathodic reduction reactions. The SEM, OP, and EDX results confirmed the adsorption and high inhibitive performance of ASP-based inhibitor. The ASP-based formulation is a potential inhibitor for oil well acidizing process