Comparative Evaluation of Pterocarpus osun and Hibiscus sabdariffa Plant Extracts as Eco-Friendly Corrosion Inhibitors for Mild Steel in Hydrochloric acid

Abstract

The study is a comparative analysis to evaluate the inhibition efficacies of two plant extracts; Pterocarpus 
osun (PO) and Hibiscus sabdariffa (HS), to mitigate the corrosion rate of mild steel in hydrochloric acid. 
The solutions used for the tests were prepared by extraction through refluxing the ground plant parts in 
ethanol, and using the extracts to prepare solutions of 100-3000 mg/dm3 concentrations.  The corrosion 
inhibition performance was tested on mild steel coupons using weight-loss and potentiodynamic 
polarization techniques in 0.1 M and 1.0 M HCl media. The corrosion experiments spanned for a period of 
120-hour at 24-hour interval of suspension, retrieval of the metal coupon and re-weighing to measure 
weight loss, and subsequently calculating the inhibition efficiencies were carried out. Results indicate that 
both PO and HS significantly reduced corrosion rates, with inhibition efficiencies reaching up to 98.9% for 
PO and 96.9% for HS at higher concentrations. The results showed decreased weight loss and reduced 
corrosion rates in the company of PO and HS at higher concentrations. The polarization results showed that 
both extracts functioned as mixed-type inhibitors. The study confirms PO and HS as effective, renewable 
and sustainable inhibitors for the corrosion of mild steel in acidic system: and can be utilized in industrial 
settings for economic benefits.