Raphia hookeri gum as a potential eco-friendly inhibitor for mild steel in sulfuric acid

Exudate gum from Raphia hookeri (RH) was tested as corrosion inhibitor for mild steel in H2SO4 using weight loss and hydrogen evolution techniques at 30–60 °C. Results obtained revealed that RH act as corrosion inhibitor for mild steel in sulfuric acid medium. The corrosion rates in all concentrations studied increased with rise in temperature. The inhibition efficiency was observed to increase with increase in RH concentration but decreased with rise in temperature, which is suggestive of physical adsorption mechanism. The inhibitive action of RH is discussed in view of the adsorption of its phytochemical components onto steel surface, which protects the metal surface and thus do not permit the corrosion process to take place. The adsorption of the exudate gum onto the steel surface was found to follow the Langmuir adsorption isotherm. The free energies for the adsorption process and the apparent activation energies, enthalpies and entropies of the dissolution process were determined. The fundamental thermodynamic functions were used to glean important information about the RH inhibitory behavior. The results were explained in terms of chemical thermodynamics.