Surface Morphology of Q235 Mild Steel Using Selected Medicinal Plant Extracts: Phytochemical and SEM - ImageJ Surface Analysis
Janet O. Akpomie *
Department of Chemistry, Faculty of Physical Sciences, Federal University of Lafia, PMB 146, Lafia 950101, Nasarawa State, Nigeria.
Amos I. Ambo
Department of Science Laboratory Technology, Faculty of Life Sciences, Federal University of Lafia, PMB 146, Lafia 950101, Nasarawa State, Nigeria.
S. P. I. Ogah
Department of Chemistry, Faculty of Physical Sciences, Federal University of Lafia, PMB 146, Lafia 950101, Nasarawa State, Nigeria.
Timothy M. Akpomie
Department of Chemistry, Faculty of Physical Sciences, Federal University of Lafia, PMB 146, Lafia 950101, Nasarawa State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
This study evaluated the corrosion inhibition behaviour of selected medicinal plant extracts on Q235 mild steel using qualitative phytochemical screening, scanning electron microscopy (SEM), and ImageJ-assisted surface morphology analysis. Fresh leaves and stems of Calotropis procera, Euphorbia kamerunica Pax, Camellia sinensis, Azadirachta indica, and Cymbopogon citratus were collected from Shabu, Lafia North Development Area of Nasarawa State, Nigeria. A 50:50 blended extract of Calotropis procera and Euphorbia kamerunica was also prepared to examine whether combining phytochemically different plant species could improve surface protection. Following air-drying and pulverization, the plant materials were extracted by cold maceration using distilled water. Preliminary phytochemical screening was carried out to identify the principal secondary metabolites present in each extract. Q235 mild steel coupons were subsequently coated with the extracts and exposed under ambient laboratory conditions for twenty days before surface examination by SEM. The resulting micrographs were further analysed with ImageJ software to obtain quantitative information on surface roughness, porosity, particle distribution, and surface coverage. The phytochemical screening confirmed the presence of several bioactive constituents: alkaloids, flavonoids, tannins, phenols, saponins, glycosides, steroids, diterpenes, quinones, phytosterols, and resins, although their distribution varied among the different plant species. SEM observations revealed pronounced differences between treated and untreated specimens. The unprotected mild steel surface exhibited extensive corrosion damage, characterised by widespread pitting, roughened regions, surface cracks, and thick accumulations of corrosion products. In contrast, specimens treated with the plant extracts generally displayed lower pit density, fewer surface defects, and evidence of adsorbed organic films. Even so, none of the extracts produced a completely continuous protective layer, as localized pores, microcracks, and discontinuities remained visible to varying degrees. ImageJ-assisted analysis supported the SEM observations by demonstrating considerable spatial variation in surface morphology. Differences in pixel intensity, roughness, porosity, and surface coverage indicated that adsorption of phytochemical constituents occurred unevenly across the steel surface. Among the extracts evaluated, the blended formulation of Calotropis procera and Euphorbia kamerunica appeared to provide comparatively better surface coverage than several of the individual extracts. While the present investigation did not directly quantify synergistic interactions, the improved surface characteristics may suggest that combining phytochemically diverse extracts enhances adsorption behaviour and promotes the formation of a more effective protective layer.
Keywords: Q235 mild steel, medicinal plants, phytochemical screening, scanning electron microscopy, imageJ analysis, surface morphology, green corrosion inhibitors