This paper describes the use of green eco-friendly lignin and its sulfonated product of natural polymer as corrosion inhibitor on the mild steel in acidic condition. Lignin was isolated from palm oil fruit bunch by acidic precipitation method and characterized by FTIR to confirm the functional groups. The inhibition effectiveness of lignin and sulfonated lignin against corrosion rate was observed by varying the concentration of lignin and metal immersion time in acidic medium. The work that is reported in this dissertation aimed at investigating the corrosion inhibiting properties of lignin and sulfonated lignin derived from selected agro-waste plants in Tanzania on mild steel in acidic media. Lignin was isolated from palm oil fruit bunch then chemically modified into sulfonated lignin by sulfonation reaction. The utilization of FT-IR results confirmed that the extracted lignin from selected agro wastes and modification into sodium lignosulfonate was successful. Potentiodynamic polarisation and electrochemical impedance spectroscopy techniques were used for investigating the corrosion inhibiting properties of lignin and sulfonated lignin derived from selected agro-waste plant on mild steel in 0.1 M HCl at room temperature.