F. Zulkifli

Study of Henna (Lawsonia inermis) as Natural Corrosion Inhibitor for Aluminum Alloy in Seawater

Commercial henna (Lawsonia inermis) was investigated to inhibit the corrosion of aluminum alloy through immersion in seawater. The aluminum alloy (5083) was prepared in size of 25mm × 25mm × 3mm. The immersion test was conducted in seawater with different concentration of henna, 100ppm, 300ppm, 500ppm for duration of 60 days. Four characterizations were performed in this study which was weight loss study, Fourier Transform Infrared (FTIR), Electrochemical Impedance Spectroscopy (EIS) and adsorption isotherm. The results indicated that henna has major constituents of lawsone which contributed to the chemisorptions or adsorption process by forming an isolation layers on the aluminum alloy surface which follows the Langmuir adsorption isotherm. It was found that the protection layer attached on metal was not permanent and precipitation occurred as the time increases. The highest inhibition efficiency was found at 88% (500ppm). This research found that henna is an excellent natural inhibitor for aluminum alloy in seawater.

The Effect of Concentration of Lawsonia inermis as a Corrosion Inhibitor for Aluminum Alloy in Seawater

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, , 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.

Non-destructive tests on eco-friendly anti-corrosion paint

Henna is identified as an excellent corrosion inhibitor and due to this reason, a research project was conducted in order to investigate the ability of henna extracts to act as an anticorrosive agent with the compatible composition for paint systems. The paint composition consisted of colophony (WW types), plasticiser (oleic acid), pigment (calcium carbonate), solvent (mixture of xylene/white spirit) and additives (zinc oxide and henna leaf extract). These ingredients were mixed until they were soluble and stirred using a high-speed disperser. In order to measure the effectiveness of the new paint system, several nondestructive tests were conducted to investigate the inhibitive properties of henna extract including measurement of substrate mass loss. The inhibition efficiency (IE) increased with the increasing amounts of inhibitor. The highest IE (%) was 77.63% and this was produced by the paint with 8% inhibitor (P3). However, the IE value started to decrease when 12% of henna extract was incorporated into the paint matrix (P4: 58.40%). Thus, P3 acted as an optimum paint with respect to its performance on the corrosion inhibition efficiency based on mass loss measurement and electrochemical studies. Surface analyses were carried out using infrared thermography and scanning electron microscopy. These surface analysis test was carried out to support mass loss and electrochemical study. Based on the results, the performance of henna extract as a corrosion inhibitor on aluminium surface showed a great impact with the 8% of henna extract presence in the paint formulation.

Protection against Corrosion of Aluminum Alloy in Marine Environment by Lawsonia inermis

The corrosion performance of aluminum alloy 5083 (AA5083) was investigated in the splash zone area simulated in salt spray cabinet at ambient temperature. Three paint formulations were prepared in accordance with different percentages of henna extract. FTIR method was used to determine the constituent of henna while weight loss and electrochemical method were applied to investigate the inhibition behaviour. The findings show that corrosion rate of aluminum alloy decreased with the increases of henna extract in the coating formulation. The rise of charge transfer resistance ( ) value has contributed to the greater protection of the coated aluminum. The decrease in double layer capacitance value ( ) is another indicator that a better protective barrier has been formed in the presence of henna in the coating matrix.