Abstract
Lawsonia inermis also known as henna was studied as a corrosion inhibitor for aluminum alloy in seawater. The inhibitor has been characterized by optical study via Fourier transform infrared spectroscopy (FTIR). The FTIR proves the existence of hydroxyl and carbonyl functional groups in Lawsonia inermis. Aluminum alloy 5083 immersed in seawater in the absence and presence of Lawsonia inermis was tested using electrochemistry method, namely, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP). EIS and PP measurements suggest that the addition of Lawsonia inermis has caused the adsorption of inhibitor on the aluminum surface. The adsorption behavior of the inhibitor follow Langmuir adsorption model where the value of free energy of adsorption, -ΔG, is less than 40 kJ/mol indicates that it is a physical adsorption. Finally, it was inferred that Lawsonia inermis has a real potential to act as a corrosion inhibitor for aluminum alloy in seawater.
Highlights
Eco-friendly and biodegradable commodities have caused a shift towards the use of natural product instead of using toxic materials [1]
The Electrochemical Impedance Spectroscopy (EIS) measurement was performed by using alternating current (AC) signal of impedance measurements by means of Autolab PGSTAT302N with respect to the open circuit potential (OCP)
Fourier transform infrared spectroscopy (FTIR) method determines the type of vibrational band presence in Lawsonia inermis
Summary
Eco-friendly and biodegradable commodities have caused a shift towards the use of natural product instead of using toxic materials [1]. Natural products derived from various flora and fauna are believed to be safe due to their nontoxic, noncarcinogenic, and biodegradable nature [2,3,4] Heavy metals such as lead (Pb) which are produced from industry (painting, charcoal burning, and leaded gasoline) are known to be a threat to the marine environment [5]. The nature of metal surface, the chemical composition of the corrosive medium, and temperature of the reaction and on the electrochemical potential at the metal/solution interface manipulate the adsorption process [21]. To the best of author’s knowledge, the study of Lawsonia inermis as a corrosion inhibitor has never been employed to aluminum alloy in seawater. To better understand the inhibitive behavior of natural products, Lawsonia inermis as corrosion inhibitor was investigated via electrochemical impedance spectroscopy and potentiodynamic polarization. The optical study was conducted by using Fourier transform infrared (FTIR) and the quantum chemical calculation was done to determine the synergism behavior of the inhibitor
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