The effect of natural inhibitor concentration of Fumaria officinalis and temperature on corrosion protection mechanism in API X80 pipeline steel in 1 M H2SO4 solution

In this investigation, the effect of Fumaria officinalis concentration, as a natural inhibitor, and the medium temperature on the corrosion prevention mechanism of an API X80 pipeline steel alloy in the solution of 1 M H2SO4 is studied. For this purpose, corrosion behavior of the pipeline steel in the solution of 1 M H2SO4 at the presence of 0, 2, 4 and 6 g/L Fumaria officinalis inhibitor at medium temperatures of 20 degrees C, 40 degrees C and 60 degrees C was assessed. To assess the corrosion protection mechanism of the API X80 pipeline steel under these conditions, Open Circuit Potential (OCP), Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) tests were conducted. As well, Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectroscopy (EDS) detector was used to analyze the corrosion products formed on the surface of the pipeline specimens. Results of OCP and potentiodynamic polarization tests showed that Fumaria officinalis reduces the speed of both anodic and cathodic reactions. Also, AGL calculation showed that Fumaria officinalis led to the reduction of anodic and cathodic reactions through its physical-chemical adsorption on the surface and blocking of corrosion active locations. The results of EIS tests indicated that with increasing the Fumaria officinalis inhibitor, the corrosion resistance of the API X80 pipeline steel increased. As well, corrosion products analysis showed that Iron sulfide compounds were formed on the surface of the specimens. In terms of the medium temperature, results showed that increasing the temperature of the solution from 20 degrees C to 60 degrees C has led to an increased corrosion rate and efficiency reduction of Fumaria officinalis. Moreover, it was defined that the adsorption process of Fumaria officinalis on the surface of the API X80 pipeline steel at the temperature of 40 degrees Cin the 1 M H2SO4 solution followed adsorption isotherm of Langmuir.