Evaluation of Natural Products as Corrosion Inhibitors: Pinus Caribaea and Pachira Quinata Bark Extracts on Steel

Organic corrosion inhibitors derived from natural products offer valuable green alternatives, but their mechanisms of action remain unclear, making it challenging to develop highly accurate models. This study explored the use of tannin extracts from Pinus Caribaea and Pachira quinata as corrosion inhibitors for steel, which is commonly used in industries for transporting aggressive fluids. Hydroalcoholic extracts from these species were freeze-dried and chemically characterized for reactive condensed tannins and total phenolic compounds. Corrosion inhibition was evaluated using electrochemical methods, including open circuit potential (Eoc), linear polarization resistance (LPR), and polarization curves. Results indicated that Pachira quinata extracts showed about 23 % corrosion inhibition, while Pinus Caribaea extracts did not inhibit corrosion and might even accelerate it. The optimal conditions for Pachira quinata extracts were pH 12.00 and low concentrations (0.10% w/w). Statistical analysis confirmed that pH and extract concentration significantly affect LPR. Due to the complexity of natural products and the difficulty in fully elucidating their chemical structures, effective models should relate to measurable physical or chemical properties to identify active compounds. Ongoing research aims to correlate properties like FTIR spectra, antioxidant activity, HPLC data, and/or others with corrosion inhibition, potentially aiding in the prediction of new bioactive compounds and understanding natural corrosion inhibitors.