Adsorption and Inhibitive Properties of Camellia Sinensis for Mild Steel in 0.5M HCl and 0.8M H_2SO_4

摘要

The effect of Camellia Sinensis (green tea) extract as a 'green' inhibitor on mild steel corrosion in 0.5M HCI and 0.8M H_2SO_4 was studied at ambient temperature. Weight loss/corrosion rate and potential measurement techniques were used for the experimental work. The results were further analyzed using the two-factor ANOVA. Potential measurement was performed using a digital voltmeter and a saturated calomel reference electrode. Results obtained showed effective corrosion-inhibition of the extract on the mild steel test-specimens in the different concentrations of HCl and H_2SO_4 used. There was increasing inhibition performance with increasing concentration of inhibitor. In 0.5M HCl, 100% green tea gave the optimal performance with weight loss and corrosion rate of 246mg and 0.63 mm/yr respectively. A similar result was observed in 0.8M H_2SO_4 where 100% green tea gave the best results of 1226 mg weight loss and 3 mm/yr corrosion rate. ANOVA test confirmed the results at 95% confidence, and further showed that concentration of green tea extract had greater effect on potential and weight loss measurements. The Gibb's free adsorption energy signified physisorption in HCl and chemisorption in H_2SO_4 as the adsorption mechanism of plant extract molecules on the metal surface.