The inhibitory effect of guar gum (GG) as a green inhibitor has been studied using a variety of
methodologies, including weight loss, thermometric studies at 30-60 ºC. The potentiodynamic
polarization, electrochemical impedance spectroscopy (EIS) and scanning electron micrographs have
been found to the good inhibitor for mild steel corrosion in H2SO4 (pH = 1) medium. Guar gum fits to
the Langmuir adsorption isotherm when it adsorbs to metal surfaces. It has also been investigated how
adding halides (KCl, KBr and KI) will affect the process. The findings demonstrated that guar gum
concentration increased with inhibition efficiency (I%). All of the concentrations of guar gum are
shown to be promoted by the inhibitive impact of guar gum in addition to halide ions. The trend Cl– <
Br– < I– has been seen to improve inhibition efficiency (I%) and the extent of surface coverage (θ),
which suggests that the electronegativity and radii of the halide ions play a significant role in the
adsorption process. According to polarization curves, guar gum functions as a mixed-type inhibitor.
The outcomes of gravimetric studies and electrochemical procedures were in good agreement. Based
on thermodynamic characteristics and a comparison of the FT-IR spectra of pure and metal surface
product, a thorough adsorption of the inhibitor molecules on the mild steel surface was proposed.
When the synergism parameter (SI) was analyzed, it is found to be greater than unity, indicating that
synergism alone is responsible for the increased inhibitory efficiency caused by the addition of halides.
The present study deals with the evaluation of the corrosion inhibition effectiveness of the two binary mixtures of nonyl phenol (NPH) with 2, 4 dimethyl aniline (DMA) and 2 ethyl aniline (EA) at different concentration ratios (from 1:7 to 7:1) for mild steel in H2SO4(pH=1) solution by weight loss and potentiodynamic polarization method. Corrosion inhibition ability of the compounds has been tested at different exposure periods (6 h to 24 h) and at different temperatures (303 K to 333 K). The binary mixture of NPH and EA (at 7:1 concentration ratio) has afforded maximum inhibition (IE% 93.5%) at 6 h exposure period and at room temperature. The adsorption of both the inhibitors is found to accord with Temkin adsorption isotherm. Potentiodynamic polarization study reveals that the tested inhibitors are mixed type inhibitor and preferentially act on cathodic areas. Electrochemical impedance study suggests formation of an inhibition layer by the adsorption of the inhibitors on the metal surface. An adsorption model of the inhibitor molecules on the metal surface has been proposed after immersion test in the inhibited acid showed characteristic shift of N-H and O-H bond frequencies towards lower side compared to that of the respective pure samples which indicated the donation of electron pair through N and O atom of the inhibitor molecule in the surface adsorption phenomena. SEM study has revealed formation of semi globular inhibitor products on the metal surface. The comparisons of the protection efficiencies of these compounds according to their relative electron density on the adsorption centre and projected molecular area of the inhibitor molecules have been made.
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