Thermodynamic and electrochemical investigation of inhibition efficiency of green corrosion inhibitor and its comparison with synthetic dyes on MS in acidic medium

•Black Pepper extract is reported as green inhibitor for mild steel corrosion with 97% inhibition efficiency.•Organic dyes i.e., Thoron dye and Phenosafranin dye can also inhibit the Mild Steel surface in HCl medium.•Adsorption of inhibitor on the Mild Steel surface is observed by AFM.•Natural and Synthetic inhibitor follow Langmuir and Temkin adsorption isotherms.