Abstract
This paper presents the corrosion and inhibition behavior of heat-treated EN8 dual-phase steel with ferrite-martensite structure with pectin in 0.5 M sulphuric acid. The corrosion studies were performed using the weight loss method, electrochemical techniques such as potentiodynamic polarization measurements, and impedance spectroscopy. The study was done at different concentrations of pectin in the temperature range of 40 to 70 °C and immersion time of 1, 3, 5, and 7 h. The results showed that the inhibition performance of pectin has enhanced with an increase in pectin concentration and decreased with the temperature and time of exposure. From the weight loss study, highest inhibition efficiency of 76.43% was achieved at 5.0 g/L at 1 h of exposure at 40 °C. The maximum inhibition efficiency of 62% was obtained with 5.0 g/L of pectin at 40 °C by potentiodynamic polarization method. The energy, enthalpy, and entropy of activation and also thermodynamic parameters like free energy, enthalpy, and entropy of adsorption were assessed and discussed. Appropriate adsorption isotherm was fit to the obtained experimental outcomes and achieved Langmuir adsorption isotherm to be the best fit and obeyed physical adsorption. Surface analysis: scanning electron microscopy, X-ray diffraction techniques, atomic force microscopy, and energy dispersive X-ray were done with and without the addition of pectin. The metal surface appears to be uniform and smooth in the presence of pectin and adsorption was confirmed by surface analysis.
Highlights
Heat treatment is a process used to modify the properties of a material
The effect of DP EN8 F-M steel exposed to 0.5 M H2SO4 solution was studied by immersion corrosion and electrochemical measurements
From the weight loss study, highest inhibition efficiency of 76.43% was achieved at 5.0 g/L at 1 h of exposure at 40 °C
Summary
Heat treatment is a process used to modify the properties of a material. EN8 steel is plain medium carbon steel with moderate strength in an as-cast state and possible to modify the properties in a wider range. It is the most commonly used type of steel, usually used in the normalized condition. The latest development in the protection of the surface of the metal is using nontoxic inhibitors (Galo et al 2020; Hoai et al 2019; Hynes et al 2021; Manssouri et al 2021; Negm et al 2011; Pais and Rao 2021; Şahin et al 2020). Saxena et al have assessed the inhibition action of Citrus sinensis extract on C-steel corrosion in 0.5 M H2SO4 (Saxena et al 2020)
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