Corrosion Inhibition of Mild Steel in Sulphuric Acid (H2SO4) Medium of the Stem Extract of Tetrapleura Tetraptera

The inhibitive action of stem extracts of Tetrapleura tetraptera on mild steel corrosion in 1.0M & 5.0M H2SO4 solutions was studied. The stem were dried under room temperature and mechanically ground into powder form. 100g of the stem powder were extracted with a mixture of methanol/water in the ratio of 4:1 using a Soxhlet extractor for 24 hours. The extracts were distilled at 60°C in a water bath until almost the entire methanol evaporated. 4.0g of the methanol extracts were digested in 1000ml of 1M H2SO4 and 5M H2SO4 and left to cool for 24 hours and the resulting solution was filtered and stored in a 1.0L volumetric flask. The stem extracts test solutions were prepared from the stock solution by dissolving 0.5g/L, 1.0g/L, 2.0g/L and 4.0g/L of the extracts in 1L solution of 1M H2SO4 and 5M H2SO4. Phytochemical analysis was carried out and the result showed the presence of some secondary metabolites such as alkoliods, flavonoids, steroids, saponins and tannins. Weight loss (gravimetric) and gasometric techniques were used to determine the inhibition action of the stem of Terapleaura tetraptera. The results showed that stem of Tetrapleura tetraptera can function as good corrosion inhibitor in acid medium. Inhibition efficiencies (%I) of the stem of Tetrapleura tetraptera extracts was found to reach 73.69% & 50.39% for 1.0M H2SO4 while for 5.0M was 83.31% & 79.54% for gravimetric and gasometric analyses respectively. The corrosion inhibition efficiency increased with increase in the concentration of the extracts and decreased with the increase in time and temperature. The corrosion inhibition efficiency exhibited by the Tetrapleura tetraptera stem extracts is attributed to the stronger adsorption of the phytochemicals present in the plant extracts unto the mild steel. The mechanism of adsorption proposed for the Tetrapleura tetraptera stem extracts is physical adsorption. The corrosion inhibition of the stem of Tetrapleura tetraptera extracts followed Langmuir, Tempkin and Freundlich adsorption isotherm for both 1.0M & 5.0M H2SO4.