A Comparative study of mild steel corrosion inhibition performance of hibiscus sabdariffa leaf extract in different acid media

Abstract

A comparative study of mild steel corrosion inhibition performance of Hibiscus sabdariffa (HB) leaf extract on mild steel in the acidic media of 0.5M H₂SO₄ and 1M HCl was conducted over a duration of 168 hours (7 days). Gravimetric Analysis (GA) and Potentio-Dynamic Polarization (PDP) were employed as the experimental techniques. The Prediction Models (PM) of Artificial Neural Network (ANN) and Multiple Linear Regression (MLR) were used to predict the experimental data.  For the GA technique, inhibitor concentrations of 5ml, 10ml, 15ml per litre (mL/L) of corrodent were used. HB leaf extract of concentration 5mL/L of corrodent yielded Inhibition Efficiency (IE) of 92% in 0.5M H₂SO₄ and 93% in 1M HCl. In 10ml/l concentration, IE was 94% in 0.5M H₂SO₄ and 93% in 1MHCl while with 15ml/l concentration, IE of 95% in 0.5M H₂SO₄ and 94% in 1M HCl were recorded. The PDP approach showed IE of 77.9% and 82.8% in 1M HCl with 5 mg/L and 15mg/L respectively while IE 88.9% and 96% were achieved with 0.5M H₂SO₄ in 5mg/L and 15mg/L respectively.    The PMs confirmed that inhibitor concentration affected IE more than exposure time and the ANN model agreed more closely with the experimental data than the MLR model and therefore can be used to model the experimental data, namely, corrosion rate and IE, in this study.