| dc.description.abstract |
Corrosion-induced metallic degradation constitutes a persistent technological and
economic challenge across petrochemical, infrastructure, automotive, and aerospace
sectors, with annual global losses estimated at nearly USD 2.5 trillion, representing
3-4% of global gross domestic product. Mild Steel (MS), characterized by elevated
reactivity and limited intrinsic corrosion resistance due to its minimal carbon content,
remains particularly vulnerable to electrochemical deterioration in aggressive aqueous
environments. This investigation systematically evaluated the efficacy of structurally
diverse organic compounds, selecting natural plant-derived extract, pharmaceuticalgrade heterocyclic molecules (antihistamine derivatives), and the synthetic azo-dye
compounds, as potential corrosion inhibitors for MS protection in acidic chloride and
sulfate media. Electrochemical characterization methodologies, like potentiodynamic
polarization, electrochemical impedance spectroscopy and surface analytical technique
(Atomic force Microscopy), were used to elucidate inhibition mechanisms, quantify
surface coverage characteristics, and assess protective film formation dynamics. The
thermodynamic and kinetic parameter governing inhibitor adsorption were determined
through application of established isotherm models, while computational approaches
utilizing density functional theory provided molecular-level insights into electronic
structure characteristics and metal-inhibitor interaction enthalpies.
The botanical extract formulation BPE depicted maximum inhibition efficiency of
97.5%, whereas pharmaceutical-derived LT exhibited exceptional efficacy of 98.72%
in hydrochloric acid and 86.35% in sulfuric acid media at 308 K. Synthetic dye
systems TH and PSF attained inhibition efficiencies of 95.8% and 83.2%, respectively,
at 4 × 10−4 M concentration. Synergistic composite inhibitor formulations utilizing
eugenol oil with dye constituents ALZ, AMR, and PSF develop critical performance
enhancements, increasing inhibition efficiency from base eugenol efficiency of 56.37%
to 83.57%, 76.71%, and 93.62%, respectively, indicative of cooperative adsorption
phenomena & improved interfacial interaction. Comprehensive temperature-dependent
evaluation across range 308338 K revealed dynamic adsorption behavior characterized
by concentration-dependent and temperature-dependent inhibition efficiency variation.
Azure dye series compounds (D-1, D-2, D-3) demonstrated thermally activated surface
interactions, with competitive inhibitor displacement patterns evolving from D-2 ≥
D-1 > D-3 at lower temperatures to D-3 > D-1 ≥ D-2 at elevated temperatures,
consistent with chemisorptive binding mechanisms and increased thermal mobility of
adsorbed molecular species.
The integrated experimental and computational findings establish that investigated
inhibitor systems exhibit sustained high corrosion protection capability via multi-site
adsorption mechanisms, robust protective film formation and usable thermodynamic
v
driving forces governing surface localization. The plant-derived and synthetic organic
inhibitors demonstrated comparable or superior performance relative to conventional
heavy metal-based formulations, while holding substantially improved environmental
compatibility, biodegradability, and occupational safety profiles. These results provide
fundamental mechanistic understanding and quantitative validation leads development
of advanced eco-compatible corrosion inhibitor technologies for large-scale industrial
implementation in mild steel protection applications across diverse aggressive media
environments. |
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