Prospect of plant extracts as eco-friendly biocides for microbiologically influenced corrosion: A review

Chemical biocides of the antimicrobials are the most practical and efficient objects for preventing microbiologically influenced corrosion. However, biocides cause many problems, especially in the environment, due to their toxicity. Therefore, an alternative eco-friendly biocide is needed to prevent these issues. This review provided the implementation of conventional biocides and the development of eco-friendly biocides and their application prospects. Also, this review discussed the process of plant extraction, purification, and identification of active compounds and the evaluation of the biocide performance to prevent microbiologically influenced corrosion (MIC). Several studies have stated that plants with active compounds such as phenolic and flavonoid ones could prevent MIC with different percentages of inhibition efficiency (%IE around 60-90%). For example, phenolic compounds were obtained from Glycyrrhiza glabra, Salvia officinalis, and Cistus ladanifer plants. Limonoid and flavonoid compounds are found in the extract of the Neem plant. The content of active rich-sulfur compounds is found in the Allium sativum plant. Furthermore, many undiscovered plant extracts have antibacterial functions as biocides that have not been explored. For this reason, the development of plant extracts to obtain active content should be prioritized for future research. The development can include investigating optimum conditions in the drying process and the purification of active compounds for the commercialization potential of eco-friendly biocides. The next approach could be carried out by combining or partially replacing acidic or base solvents in the extraction process with water in a specific ratio. This approach reduces the use of chemicals and the formation of potential waste harmful to health and the environment. Finally, the purification and performance of eco-friendly biocides from nature, including their inhibition efficiency, should be thoroughly investigated and verified before being applied for commercial corrosion protection purposes.