Pyrazine derivatives as green oil field corrosion inhibitors for steel

The inhibitive efficacy of environmental friendly pyrazine derivatives, 2,3-pyrazine dicarboxylic acid (Pyrazine C), pyrazine carboxamide (Pyrazine E) and 2-methoxy-3-(1-methylpropyl) pyrazine (Pyrazine H), on X60 steel were investigated in 15% hydrochloric acid (HCl), which simulate oil well acidizing conditions. The inhibitors were examined for their inhibition performance utilizing weight loss measurement at 60 °C and 90 °C for 6 h and electrochemical methods namely potentiodynamic polarization (PDP), electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) at 25 °C. Results showed that efficiencies of pyrazines C and E were not affected by increase in their concentrations at 60 °C, however inhibition performance of pyrazine E increased with concentration at 90 °C while pyrazine C remained unchanged. The inhibition performance of pyrazine H increased with concentration at both temperatures. It was observed that addition of sodium Iodide (NaI) and Glutathione (Glu) enhanced the inhibition performance of pyrazine C and E but has no significant effect on pyrazine H. Potentiodynamic test showed that the three pyrazine derivatives investigated are mixed typed inhibitors. Pyrazine C and H are predominantly cathodic whereas pyrazine E was shown to be predominantly anodic. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy were utilized to further confirm the inhibition of steel corrosion by the three pyrazine derivatives.