Plant extracts: Probable alternatives for traditional inhibitors for controlling alloys corrosion against acidic media—A review

The sufficient performance and low concertation requirement are promising factors that make industries apply inhibitors in their processes. Inhibitors are promising sources to prohibit metallic samples' corrosion against harsh media. Due to the recent restrictions and standards, utilization of traditional synthetic inhibitors has been overlooked by industries and green inhibitors have been nominated as potential alternatives. Recent endeavors of researchers led to green inhibitors generation. Their interesting features including green nature and biodegradability encourage researchers to assess their inhibition ability. Their impacts have been broadly analyzed via various electrochemical (polarization and electrochemical impedance spectroscopy) and traditional (i.e., weight loss) techniques. Among the all green inhibitor types, plant extracts (including seeds, leaves, and fruit) have been interestingly appreciated. Besides the previously mentioned properties, these inhibitors are renewable and the presence of active compounds in their phytochemicals can guarantee adequate protection against metals and alloys' corrosion. They can be easily achieved by employing a simple extraction procedure, and in comparison with other types of green inhibitors (such as amino acids, fatty acids, and bio-polymers), they are widely available and quite affordable. All these characteristics make plant extracts undeniable certified sources of corrosion inhibitors. The analysis of plant extracts' anticorrosion potency was conducted by different works, and this review tried to compare their effectiveness against various acid media corrosion (i.e., H₂SO₄, HCl, and H₃PO₄).