Cleaner corrosion inhibitors using Peumus boldus Molina formulations in oil well acidizing fluids: gravimetric, electrochemical and DFT studies

Eco-friendly inhibitors are an alternative to reduce environmental and human health problems related to conventional inhibitors employed in oil well acidizing. In the present study, boldo (Peumus boldus) was investigated as a corrosion inhibitor for API P110 carbon steel in 2 M and 15% HCl. A two-level full factorial design (23) was used to evaluate the extraction time (90 and 210 min), temperature (313 and 343 K) and solute/ethanol ratio (0.15 and 0.35 g of sheet/mL of ethanol). The extracts were characterized by phenolic content, Fourier-transform infrared spectroscopy, Proton nuclear magnetic resonance, relative density and refraction index. The extract concentration in 2 M HCl was evaluated at 303 and 313 K, achieving 87% efficiency. Binary formulations were developed in order to partially reduce the use of conventional inhibitors. Two formulations performed better at 333 K. Electrochemical tests provided information about the metal-solution interface in the absence and presence of the formulations, indicating that these are mixed corrosion inhibitors. Confocal microscopy elucidated metallic surface morphology. Surface characterization techniques confirmed the presence of the inhibitory film on the metallic surface. Density functional theory indicated that the boldine molecule was stable in the acidic phase, exhibiting improved anticorrosive properties.