The corrosion inhibition of austenitic stainless steel in sea water in the presence of Allium cepa extract was studied using weight loss technique at room temperature. Austenitic stainless steel samples obtained were immersed completely in their various media of varying concentrations with and without the onion extract as inhibitor (i.e. 0.1 to 0.6g of inhibitor in 500ml of sea water). The weight loss data was recorded every 4 days for a period of 28 days. The results from the experiment showed that the weight of the stainless steel samples decreased with an increase in time exposure of the steels in the sea water. Stainless steel samples immersed in the presence of the inhibitor decreased at a lower rate as compared to the control experiment. The solution containing the onion extract also inhibited the corrosion rate of the austenitic stainless steel sample to an extent depending on the medium type. The results also revealed that the higher the concentration of the inhibitor, the higher the inhibition efficiency. The optimum inhibition efficiency was 76.43% when Allium cepa was present at 0.6g per 500ml demonstrating the onion extract as a good corrosion inhibitor that can be applied in industries which makes use of the austenitic stainless steel for their operations as well as other metals. Three adsorption isotherm models were investigated in this study namely; Langmuir adsorption isotherms was used to determine the adsorption properties. The results showed that the extract adsorb on the surface of the austenitic stainless steel through physical adsorption of which Langmuir adsorption isotherm gave the best fit and the process was spontaneous.
Corrosion, Austenitic Stainless Steel, Corrosion rate, Allium cepa, corrosion inhibitor, weight loss, adsorption.
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