Protection of J55 Steel Surface in Acidic Well Treatment Fluids Using Green Anticorrosive Oilfield Chemicals from 5-hydroxytryptophan

A non-toxic compound, 5-hydroxytryptophan (5-HTP), was investigated for its performance as inhibitor of J55 steel corrosion in both 1M and 15% HCl for the first time. The efficiency was determined using Weight Loss (WL), Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP) techniques. Inhibition efficiency obtained from WL measurement decreased from 91.4% and 73.9% in 1 M and 15% HCl respectively at 30°C to 67.4% and 40.3% in the respective acid solutions at 90°C. Blending 5-HTP with potassium iodide, polyethyleneglycol and glutathione increased the efficiency to values above 72% in both acid solutions at 90°C. The inhibitor adsorption was spontaneous and physical in mechanism, following the Langmuir adsorption model. Adsorption was also exothermic with resultant decrease in entropy of the bulk solution. Increase in 5-HTP concentration increased the charge transfer resistance but decreased the double layer capacitance. Tafel polarization study shows that 5-HTP behaves as mixed type inhibitor with anodic predominance. The corrosion products and metal surface were analysed using other techniques like SEM/EDS, FTIR, UV-VIS. The surface protection is attributed to formation of protective film of 5-HTP molecules on J55 steel surface facilitated by O, N and C=C functionalities. The resulting oilfield chemicals can be used as efficient alternative corrosion inhibitors for protection of surface and downhole steel construction materials.