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Evaluation of Extracts of Henna Leaves as Environmentally Friendly Corrosion Inhibitors for Metals
Author(s) -
AlSehaibani H.
Publication year - 2000
Publication title -
materialwissenschaft und werkstofftechnik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.285
H-Index - 38
eISSN - 1521-4052
pISSN - 0933-5137
DOI - 10.1002/1521-4052(200012)31:12<1060::aid-mawe1060>3.0.co;2-k
Subject(s) - lawsonia inermis , shampoo , chemistry , corrosion , gallic acid , active ingredient , nuclear chemistry , environmentally friendly , metallurgy , traditional medicine , materials science , antioxidant , biology , organic chemistry , medicine , ecology , bioinformatics
Water extracts of Henna, Lawsonia inermis , leaves powder were evaluated as corrosion inhibitors for steel and commercial aluminum in saline, acidic and alkaline waters. The water extracts of Henna leaves are being used as a hair dye‐staff and as a shampoo ingredient for its dermatological effects. Four commercial brands of Henna leaves, produced and distributed in Arabian peninsula and Africa, were tested; Madena, Kathem, Saudani and Yemeni. The maximum inhibition efficiency reported in this study was for extracts of 20 g of powdered Henna leaves per litre. Weight loss tests for few days showed that the extracts can inhibit efficiently the corrosion of steel 37 in HCl up to 96% and aluminum in NaOH up to 99.8% while no inhibition occurred for steel or aluminum in NaCl solutions. The inhibition efficiency was found to decrease as the corrosive concentration increased while it increased with increasing the concentration of the extract. It is believed the inhibition process occurs predominantly via chemisorption of the active species in the Henna extract, mainly, gallic acid and 2‐hydroxy‐1,4‐naphthoquinone and dextrose. These active ingredients constitute ca. 18% by weight of the powdered dry leaves. Since Henna is an environmentally friend natural product with an average price of 0.5 $ per kg of powdered henna leaves, it is recommended to consider henna leaves as a potential source for corrosion inhibition of aluminum and steel in wet environments.