Henna Extract in Styrene-Acrylic water-based Paint of Mild Steel as an Eco-Friendly Corrosion and Microbial Inhibitor

Rabie, Ayman M.; Abdelhai, F.; Hussein, Ahmed I.; Khorshed, Lobna A.; Abdo, Abdullah M.

doi:10.21608/ejchem.2025.365318.11386

Henna Extract in Styrene-Acrylic water-based Paint of Mild Steel as an Eco-Friendly Corrosion and Microbial Inhibitor

Articles in Press

Document Type : Original Article

Authors

¹ Chemistry Department, Faculty of Science, Al-Azhar University, Nasr City, 11884, Cairo, Egypt.

² Polymer and pigments Department, National Research Center , 33 El Bohoth Street, Dokki, P.O. Box,12622, Giza, Egypt

³ Physical Chemistry Department, National Research Center , 33 El Bohoth Street, Dokki, P.O. Box,12622, Giza, Egypt

⁴ Botany and Microbiology Department, Faculty of Science, Al-Azhar University, Nasr City, 11884, Cairo, Egypt.

10.21608/ejchem.2025.365318.11386

Abstract

Corrosion of mild steel in extreme environments is a major challenge, requiring sustainable protective coatings. This study investigates the potential of Lawsonia inermis L. (henna) extract as a sustainable, bio-based additive to enhance corrosion resistance and antimicrobial properties in styrene-acrylic water-based paint. Fourier Transform Infrared (FTIR) spectroscopy identified key functional groups responsible for bioactivity. A broad peak at 3360.07 cm⁻¹ indicated hydroxyl (–OH) groups, linked to phenolic compounds with antimicrobial properties. A peak at 2926.13 cm⁻¹ represented C–H stretching from aliphatic structures, while the peak at 1632.07 cm⁻¹ confirmed the presence of carbonyl (C=O) groups, associated with anticorrosive activity. Aromatic C=C stretching at 1513.21 cm⁻¹, along with peaks for C–O and C–N stretching, confirmed the presence of esters, ethers, and amine groups contributing to bioactivity.
Elemental analysis (EDAX) revealed a high carbon (42.65%–43.99%) and oxygen (42.32%–54.31%) content, indicating the presence of elements of bioactive compounds like phenolics, flavonoids, and organic acids. Significant calcium content (up to 35.81%) supports strong adhesion properties, while trace chlorine and iron indicate antimicrobial and anticorrosive potential. Elemental mapping confirmed uniform distribution of key elements, enhancing bioactivity and surface protection.
SEM analysis revealed rough, porous morphology, promoting better adhesion and forming a physical barrier to corrosive agents. Antimicrobial testing showed significant activity minimal inhibitory conc. (MIC) at 1.5 g/100ml henna extract, with inhibition zones ranging from 9.3 to 15.5 mm against bacterial organisms Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus , Escherichia coli, Pseudomonas aeruginosa, and Proteus vulgaris and ranging from 11.4 to 13.1 mm against fungi Aspergillus fumigatus, Penicillium italicum and Cryptococcus neoformans.
Corrosion tests using immersion in 35 ppt artificial seawater salt solution for 28 days indicated that a 1.5% henna extract formulation (TP3) improved corrosion resistance, reducing pit formation and tarnishing. TP3 also maintained optimal viscosity (4400 cP), strong adhesion (5B), and high hardness (H), demonstrating resistance to acid, alkali, and water.
These findings confirm L. inermis extract as an effective, eco-friendly additive for antimicrobial and anticorrosive paint applications, with potential for industrial scalability and enhanced durability in extreme environments.

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