Investigation of the Inorganic Anion Complex of Amidoamine Derived from Synthetic Petroleum Acid as a Corrosion Inhibitor

Abstract

The study covers the synthesis of an inorganic anion-containing complex of amidoamine synthesized on the basis of the reaction of synthetic petroleum acid and diethylenetriamine in a molar ratio of 2:1, the determination of its chemical structure, and the investigation of its effect as a corrosion inhibitor on steel surfaces in a CO₂ medium. The obtained complex had an inorganic anion-containing HBr complex composition at a ratio of 1:3. The composition and structure of the synthesized complex were analyzed by infrared spectroscopy and nuclear magnetic resonance spectroscopy methods.

The effect of the inhibitor solution on the corrosion process of a C1018 steel electrode was investigated in CO₂-saturated seawater. For this purpose, potentiodynamic polarization measurements were carried out using the CORRTEST CS Studio 6 system at 50°C for 3 hours. It was determined that the inhibitor showed a protective effect at concentrations of 100, 200, and 300 ppm and effectively weakened the corrosion process.

The protection efficiency of a 20% solution of the complex in isopropyl alcohol was 91% at 100 ppm, 93% at 200 ppm, and 97% at 300 ppm. Based on the results of the potentiodynamic polarization analyses, it was established that the investigated inhibitor has high efficiency as a mixed-type corrosion inhibitor for C1018 steel in CO₂-saturated seawater.