Effect of the Diesel, Inhibitor, and CO₂Additions on the Corrosion Performance of 1018 Carbon Steel in 3% NaCl Solution

Abstract

In order to determine the diesel contribution in the coadsorption process of the oil-soluble inhibitors, electrochemical impedance spectroscopy measurements have been carried out to study the performance of oil-soluble inhibitors in both presence and absence of diesel and CO2. The results showed that the presence of the oil phase provides some protection to the steel because the water-soluble fractions are capable of being adsorbed on the steel surface thereby reducing the corrosion rate. The oily phase does not contribute to the adsorption process of the inhibitor because the inhibitor is absorbed into the water-soluble fractions. The oil-soluble inhibitors are effective only when the solution is saturated with CO2. CO2saturation causes a decrease in the pH of the solution causing both an increase of the inhibitor solubility and a better dispersion of the inhibitor into the electrolyte.

Biodiesel from “Morelos” Rice: Synthesis, Oxidative Stability, and Corrosivity

“…From the phase angle spectrum, it is possible to observe only part of the characteristic shape (Gauss bell shape) of the phase angle corresponding to one single time constant. However, the width of this time constant suggests that there are actually two overlapping time constants which evolve from the high frequency region to the intermediate frequency region; something similar has been reported when an oily film is adsorbed by the metal surface [54][55][56][57]59]. Therefore, the response observed in the region of high frequency (>1000 Hz, phase angle maximum practically constant and close to 90 ∘ ) represents the capacitive response of biodiesel, and that observed in the intermediate frequency region (10-1000 Hz, phase angle maximum variable) is due to the corrosion process in the steel-biodiesel interface [60].…”

“…However, due to the high resistivity of biodiesel, it is not obvious to associate such response with the corrosion processes at the metal-electrolyte interface [20]. However, despite this, the analysis of the Bode diagram can differentiate the capacitive response of biodiesel from the response of the stainless steel corrosion process [54][55][56][57][58]. From the phase angle spectrum, it is possible to observe only part of the characteristic shape (Gauss bell shape) of the phase angle corresponding to one single time constant.…”

Sustainable Development of Palm Oil: Synthesis and Electrochemical Performance of Corrosion Inhibitors

“…These characteristics (slope lower than -1, and phase angle less than 90 o ) are typical of non-capacitive surface layers where the corro-sion process can be under mixed control (diffusion and charge transfer). Moreover, the shift towards lower frequencies of the phase angle, as well as decreasing slope, can be associated with a detachment or thinning of the protective layer [9,11,35]. Finally, in the low frequency region (f < 1 Hz), the dispersion of experimental data is observed, besides the apparent presence of a plateau.…”

“…According to the observed characteristics, the corrosion resistance of carbon steel decreases constantly and adsorption-diffusion processes are observed. This may be due to absorption of intermediate species (FeOH) derived from the hydrolysis of iron, or due to adsorption of the water-soluble fractions (WSF's) of the diesel [9,11,36]. Fig.…”

“…Corrosion inhibitors can be organic or inorganic substances. In particular, corrosion inhibitors of organic nature have in its structure two essential components; a polar end (rich in electrons) formed by heteroatoms (such as oxygen, nitrogen, and sulfur), with the ability to be adsorbed (through coordination bonds) onto an electrovalent metal surface (since it has additional external electrons to fill the vacant or share with the d orbital of the metal surface), and a hydrophobic end (hydrocarbon tail) which can efficiently repel the contaminants of the aggressive electrolyte [5][6][7][8][9][10][11][12][13]. These kind of organic corrosion inhibitors are widely used in the oil and gas industry to protect the carbon steel pipelines against internal corrosion.…”