Synthesis, characterization, and evaluation of polymeric surfactants derived from PET plastic waste as green corrosion inhibitor of steel surfaces in marine environment for heavy industry

Abstract

The aim of this work was to prepare a nonionic polymeric surfactant from a recycled product of poly(ethylene terephthalate) plastic waste, PET. In this respect, PET waste was subjected to reverse polymerization (depolymerization) via reaction with both ethylene diamine (EDA) in the presence of a catalyst and propylene glycol (PG) in the presence of a transesterification catalyst. The corresponding products obtained were poly amino amide (PETAA) and poly glycol ester (PETPG), respectively. The obtained materials reacted with oleic acid to produce N1,N4-bis(2-((E)-octadec-9-enamido)ethyl)terephthalamide (PETAA-OL) and 2-(2-(((E)-octadec-8-enoyl)oxy)propoxy)ethyl (2-(2-(((E)-octadec-9-enoyl)oxy)propoxy)ethyl) terephthalate (PETPG-OL). The prepared materials were characterized by FT-IR, ¹HNMR, and elemental analysis. It was evaluated as a corrosion inhibitor for carbon steel used in the petroleum industry in the marine environment. Chemical, analytical, and electrochemical techniques were used for the evaluation of the corrosion inhibition efficiency of the prepared polymeric surfactants. The effects of the polymeric surfactant concentration and reaction temperature were studied. The inhibition efficiency was found to increase with increasing concentration and decrease with rising temperature. The inhibition due to the adhesion and adsorption of the polymeric material on the steel surface agrees with the Langmuir adsorption isotherm model. The amount of dissolved iron in the corrosive medium due to the corrosion process was estimated using atomic absorption spectroscopy (AAS). It was found that the dissolution of iron was decreased by adding the prepared nonionic surfactants. Potentiodynamic polarization data indicate the mixed-type nature of surfactant inhibitors. According to the potentiodynamic polarization data, the prepared surfactant boosts polarization resistance and inhibition performance by adsorbing on the metal/electrolyte interface. The addition of inhibitor molecules to the aggressive medium produces a negative shift in the open-circuit potential due to the retardation of the cathodic reaction. The surface morphology of steel was examined using SEM. A protective coating of inhibitor molecules forms on the steel surface, according to the SEM measurements of the surface. The data obtained from different techniques are in good agreement, indicating good inhibition efficiency of the prepared nonionic surfactants derived from plastic waste in a marine environment.