ABSTRACT

Imidazoline derivatives have anti-corrosive effects on metals such as carbon steel and are widely used in acid-corroded pipelines for conveying oil and natural gas. In this paper, a novel imidazoline inhibitor was designed and synthesized. The corrosion inhibitor has excellent corrosion inhibition effect on in the environment of H2S / CO2. When the dosage is only 50mg / L, the corrosion inhibition efficiency can reach 94 %. SEM observation shows that fewer pits and corrosion product were found on the sample surface after adding the corrosion inhibitor. The adsorption performance of imidazoline derivatives on Fe (001) surface was calculated by molecular dynamics simulation. The molecular dynamics simulation showed that imidazoline derivatives had bigger adsorption on water than Fe (001), so that the corrosion inhibitor will first be adsorbed on the iron surface to play a role in the inhibition of corrosion, the frontier orbital adsorption sites of the corrosion inhibitor molecules are distributed around the phenyl group, thereby forming a more stable adsorption film on the metal surface.

INTRODUCTION

Corrosion of the metal is a severe problem of industrial production and oil field transportation, which brings not only the waste of resources but also environmental pollution. To solve the corrosion problems, adding corrosion inhibitor is a convenient, economical and effective method. Imidazoline derivatives, a kind of environmental-friendly corrosion inhibitors, can effectively inhibit carbon steel corrosion in an acidic environment1-6. With the enhancement of people's awareness of environmental protection, the research on new type of corrosion inhibitor is developing towards the targets of high efficiency, multi-function and pollution-free. Imidazoline corrosion inhibitors are the hot topics of current research due to their high efficiency, low toxicity and good biodegradability.

The molecular structure of imidazoline inhibitor contains a hydrophilic group, five-membered heterocyclic ring, and a hydrophobic group. Each group has its role, such as hydrophilic group can increase water solubility, and hydrophobic group hinders the corrosive medium close to the metal surface. The change of imidazoline molecular structure can change the corrosion inhibition performance7. In this paper, an imidazoline inhibitor containing three phenyl groups was designed and analyzed. The frontier orbitals, molecular dynamics simulation, micro-corrosion morphology and corrosion inhibition performance of imidazoline inhibitor were analyzed by computer simulation, weight loss method, electrochemical method, and scanning electron microscope.

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