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[Display omitted] • Two biosurfactants, POCI and SOCI, derived from oleic acid were developed for inhibition of sour corrosion. • The number of hydroxyl groups in the biosurfactants significantly impacts their corrosion inhibition performance. • SOCI, with more hydroxyls, showed significantly better performance than POCI. • More hydroxyl groups in SOCI facilitate stronger adhesion to the steel surface, leading to improved protection. • Hydroxyl-rich biosurfactants are environmentally friendly corrosion inhibitors for sour mrdium. Oil and natural gas remain crucial for meeting global energy demands, but their extraction and processing face significant challenges due to sour corrosion. This study explores the influence of hydroxyl groups on the performance of biosurfactants, specifically sorbitol oleate (SOCI) and pentaerythritol oleate (POCI), in sour environments. This study reveals that the presence of more hydroxyl groups in inhibitor molecules significantly enhances their effectiveness against sour corrosion. A weight loss study showed that the corrosion rates dropped to 0.033 mm y−1 for POCI and 0.005 mm y−1 for SOCI from an initial rate of 0.490 mm y−1 in the blank solution, indicating the superior inhibition efficiency of SOCI (98.9%) compared to POCI (93.3%) at 24 × 10−4 M. Electrochemical measurements corroborated these findings, demonstrating increased corrosion resistance and reduced current densities in the presence of both inhibitors, with SOCI exhibiting better performance. The inhibition mechanism involves a combination of physical and chemical adsorption. Density functional theory calculations indicated the role of hydroxyl groups in enhancing adsorption and corrosion inhibition efficiency, with SOCI exhibiting a smaller energy gap, lower hardness, and higher softness compared to POCI. MD simulations confirmed the stable adsorption of both inhibitors on the Fe (110) surface, with SOCI showing a more favorable orientation and stronger interaction due to its higher number of hydroxyl groups. This facilitates stronger adsorption on the CS surface and the formation of a more robust protective film. The combined experimental and computational findings highlight the importance of molecular structure, film-forming ability, and hydroxyl content for the design and development of next-generation hydroxyl-rich biosurfactants for mitigating sour corrosion in the oil and gas industry. [ABSTRACT FROM AUTHOR]