Paper Title
An Aqueous Extract of Macadamia Green Peel Bio-Waste as a Potential Green Mild Steel Corrosion Inhibitor in an Acidic Electrolyte

Abstract
Improving the corrosion resistance of mild steel in an acidic aqueous environment is an important industrial process due to the use of acids for descaling and cleaning. The application of corrosion inhibitors is one of the most effective, simple and economical means of protecting metals against corrosion. Plant-derived compounds have recently gained attention due to their low cost, non-toxic, and environmentally friendly properties. Bio-wastes are recognized as a potential cheap source of green corrosion inhibitors, and their use can help reduce the amount of wastes discharged into the environment. Green peel bio-waste (GPBW) generated from the macadamia nut processing is typically dumped into the environment, posing disposal concern. This research investigated the use of GPBW as a source of green organic compounds useful for mild steel corrosion inhibition in an acidic solution (2 M HCl) using gasometric and optical methods. Results showed that mild steel corrosion rates decreased as extract concentrations increased. As a result, mild steel corrosion inhibition increased with increasing inhibitor concentration and reached a peak value of 81% at 0.5 g/ml extract concentration. The optical images showed that the inhibitor molecules adsorb on time metal surface to form a protective film that isolates the mild steel from the corrosive solution. The adsorption of inhibitor molecules on the mild steel surface followed the Langmuir adsorption isotherm, indicating the formation a monolayer film and homogeneous distribution of adsorbed molecules. The Gibbs free energy (G‚ó¶ads) value of -24 kJ/mol indicated that the inhibition process is mainly characterized by physical adsorption. The results of this study suggest that the aqueous GPBW extract could serve as an inexpensive, non-toxic, and renewable metal corrosion inhibitor in the acidic solution. Keywords - Acidic Solution, Corrosion Inhibition, Macadamia Green Peels, Mild Steel.