An Insight on Preparation and Corrosion Inhibition of Monoethanolamine Borate

Introduction: Acids usage for industrial cleaning, acid pickling, scale removing treatments, well acidizing procedure in oil and gas industry etc., cause serious corrosion problems. Several corrosion inhibitors have been... [ view full abstract ]

Introduction: Acids usage for industrial cleaning, acid pickling, scale removing treatments, well acidizing procedure in oil and gas industry etc., cause serious corrosion problems. Several corrosion inhibitors have been employed to reduce or prevent destruction or degradation of metal surface. In general, organic type inhibitors act efficiently due to chemically adsorption or chemisorption on the surface of the metal. Adsorption tendency is related to the presence of polar functional groups (N, O or S atoms) in the molecule, heterocyclic compounds and pi electrons. This work presents a synthetic route for monoethanol borate, and evaluation of the compound as an inhibitor in acidic environment.

Methods: Boric acid (BA) was reacted with monoethanolamine (MEA) in aqueous medium by gradual increase of temperature to 145 °C. The reagents BA and MEA were employed in a 1:2 molar ratio to synthesize the product referred as MEAB. The chemical structure of MEAB was characterized by means of FT-IR and NMR spectroscopy, D₂O were used as a solvent in the latter case. The electrochemical measurements were performed by potentiodynamic polarization technique. A corrosion cell system consisting of a Type 430 stainless steel specimen with an area of 5cm² as a working electrode, graphite rods as counter electrodes and a saturated calomel electrode (SCE) as reference was used. Corrosion tests were conducted in the de-aerated inhibitor solution at 30 °C as mentioned in ASTM G59 and procedure explained therein was followed.

Results and Discussion: The boron based product MEAB was prepared as viscous yellow liquid, exhibits homogenous appearance and a pH of 12. The chemical structure of MEAB was investigated with FT-IR and ¹H-NMR analyses. Polarization resistance values for Type 430 stainless steel specimen immersed in 0.5 M of H₂SO₄ solutions containing different concentrations of MEAB were obtained. In terms of resistance to general corrosion for the test specimen when acidic solutions with and without MEAB are compared, MEAB is suggested as a corrosion inhibitor.