Corrosion protection of Q235 steel in acidic-chloride media using seed extracts of Piper guineense

Abstract

The seed extract of Piper guineense (PGS) was investigated as an eco-friendly and cost-effective anticorrosion agent for the protection of Q235 carbon steel in acid chloride medium (0.25 M H2SO4 + 0.5 M NaCl), using a sequence of experimental and computational techniques. The phytochemical constituents of PGS seed extract were verified with a combination of GC-MS and FTIR analysis. Corrosion experiments involving gravimetric and electrochemical measurements, as well as surface imaging (AFM, SEM) and characterization (XPS) techniques all confirmed remarkable and sustainable anticorrosion performance of PGS. The impedance data revealed strong interfacial adsorption of phytochemical constituents of PGS on the steel surface, while polarization measurements confirmed their simultaneous inhibiting effects on both the cathodic and anodic reactions of the corrosion process. The extract was found to sustain its remarkable anticorrosion efficiency (˃ 98%) for prolonged time intervals (up to 144 h) without replenishment. The surface coverage of the extract constituents on the steel surface followed the Langmuir adsorption isotherm model. The adsorption strengths of some major phytochemical constituents of the extract on iron were computed using molecular dynamics simulations in the context of the density functional theory (DFT). The large negative values of the computed adsorption energies corroborate the remarkable anticorrosion performance of PGS extract as observed from the experimental data.