A study on green corrosion inhibitors for inhibiting corrosion on mild steel in oil well simulating brine

Abstract

Corrosion causes early failure of construction materials due to degradation and destruction of the metal in contact with corrosive ions. Mild steel is widely utilized in industries such as oil and gas wells because it is inexpensive, has high strength, and is readily available. In the oil and gas exploration and production section, the corrosion cost is $1.37 billion each year. Furthermore, chloride ions present in the formation water of oil wells, which cause pitting attacks on mild steel, are the most corrosive of the ions found in oil and gas well formation waters. Literature survey revealed that less work has been carried out to inhibit the localized corrosion of mild steel in the presence of chloride ions after more prolonged exposure. The current study focused on the use of inhibitors such as surfactants (organic compounds), surfactants and ionic liquids (organic organic combination), rare earth metal salts (inorganic compounds), and rare earth carboxylate compounds (inorganic-organic combination) to inhibit the localized corrosion of mild steel in corrosive NaCl solution. Chapter 1: Introduction and Literature Review This thesis chapter covers the fundamentals of corrosion, its history, and its adverse effects on metal. Furthermore, it describes its economic influence in various industries and research studies that offer multiple methods of corrosion control. A review of the literature survey shows that application of corrosion inhibitors are mostly applied and among the least costly techniques to inhibit corrosion from pipes. The review reveals few gaps in the field of corrosion inhibition, which serves as motivation to conduct the investigation. Finally, the established research objectives were defined to steer the thesis logically. Chapter 2: Materials, Methods, and Theories This chapter comprises the amalgamation of all the materials (i) commercially available and (ii) synthesized in the lab. Also included are the methods followed in various corrosion testing, weight loss, electrochemical polarization, electrochemical impedance, etc. methods for corrosion rate identification and the associated theories. After the exposure of mild steel in NaCl solution without and with the addition of an inhibitor, the layer formed above the metal was characterized through various techniques like FESEM coupled with EDS, XRD, FTIR, and Raman i spectroscopy, which are explained in details. Further, the isotherms present the adsorbent application, which includes Langmuir adsorption isotherm. Chapter 3: Synergistic Inhibition Effect of Imidazolium Ionic Liquid and Sodium Dodecyl Sulfate (SDS) for Mild Steel in NaCl Solution This chapter investigates the effect of varying concentrations of SDS, DMImCl, and a mixture of SDS and DMImCl. Weight loss and electrochemical polarization techniques were employed to calculate the corrosion rate, and experimental results reveal that adding a mixture of 200 ppm SDS/200 ppm DMImCl inhibitors sufficiently minimizes the corrosion rate. Chapter 4: Comparison Study of Inhibition Efficiency of Cerium Nitrate with Cerium Tartrate for Mild Steel in NaCl Solution The current chapter investigates the effect of adding an organic component (tartrate) on the inhibition efficiency of cerium nitrate. This study produces cerium tartrate (CeTar) by precipitating cerium nitrate with potassium sodium tartrate (KNaTar). Weight loss tests and electrochemical testing indicated that the inhibition efficiency decreased by adding cerium nitrate. Still, the cerium tartrate inhibitor demonstrated a nearly constant inhibition efficiency for up to 30 days. Chapter 5: Investigate the Effect of Cation on the Inhibition Efficiency of Various Rare Earth Tartrates This section of the chapter investigates the effect of rare earth metals (RE- Y, La, and Nd) on the inhibitory efficacy of synthesized rare earth tartrate (RETar) compounds against mild steel corrosion in neutral NaCl solution. These compounds hinder mild steel corrosion by forming bimetallic complexes and metal oxides/hydroxides. The experimental results demonstrate that CeTar imparts the most inhibition, while YTar offers the least. Therefore, the examined rare earth metal has the following order of inhibitory efficiency: Ce>Nd>La>Y. Chapter 6: Summary and Future Prospects This chapter summarizes the significant findings of this thesis. The 3rd chapter of the thesis illustrates the efficacy of the mixture of organic compounds. The result shows that the mixture ii of two compounds synergistically inhibits the corrosion more effectively than the single components. Then, in the 4th chapter, inhibition efficacy was studied by the mixture of inorganic and organic compounds. The outcomes of these studies show that the mixture of organic and inorganic inhibitors gives more promising results than the inorganic and organic-organic inhibitors. This is because the organic and inorganic compounds follow different adsorption mechanisms. The study's findings on rare earth carboxylate compounds offer valuable insights into utilizing inhibitors in NaCl corrosive solutions for industrial applications and propose potential areas for future research in the presence of another corrosive environment in the oil well.