Browsing by Author "Weeraratne, A. D. K. I."

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Inhibition of aluminum corrosion using self-assembled layers of Zn(Ⅱ) metal complex
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Harindi, W. A.; Weeraratne, A. D. K. I.
Metals naturally undergo corrosion, resulting in the formation of oxides that are more chemically stable. The most prevalent type of corrosion is caused by the electrochemical oxidation of metal through reaction with an oxidant such as hydrogen, oxygen, or hydroxide. Aluminum and its alloys are an important category of materials because of their great technological value and extensive industrial applications, particularly in the household and aircraft sectors. While aluminum's naturally occurring oxide layer protects it from corrosion in a variety of media, numerous studies have demonstrated that this layer can be damaged, and that metal can corrode when exposed to solutions containing chlorides in particular. Pitting corrosion is a common form of localized corrosion often observed in aluminum or aluminum alloys when exposed to chloride environments. Corrosion inhibitors are commonly used to minimize the harmful effects of corrosion. The main objective of this research project is to investigate the effectiveness of self-assembled layers of a redox innocent metal complex in inhibiting the pitting corrosion of aluminum. Here, a newly synthesized Schiff-base Zn(II) metal complex was studied as a corrosion inhibitor for aluminum substrates in chloride containing environments. The Schiff-base Zn(Ⅱ) metal complex was synthesized by the reaction of Schiff base ligand (2,4-Di-tert-butyl-6- (4chlorophenyliminomethyl) phenol) and ZnCl2 in hot methanol. The mixture was refluxed for 3 h, followed by cooling at room temperature. The pale-yellow color solid was filtered off and dried under vacuum. The yield was 70%. Synthesized Zn(Ⅱ) metal complex was characterized using Thin Layer Chromatography (TLC), Fourier Transform Infrared (FTIR) spectroscopy, and UV-visible spectroscopy. The FTIR spectrum showed characterized peaks at 1582 cm-1 for C=N stretching vibration and 517 cm-1 for Zn-N starching vibration. The self-assembled layer technique was used to form films on the aluminum surface. The films were characterized using contact angle measurement, and they exhibited a contact angle of 108.038°, demonstrating good hydrophobicity. Finally, corrosion inhibition evaluation was done qualitatively and quantitatively using scanning electron microscope (SEM) images, and electrochemical impedance spectroscopy (EIS). SEM images showed that corrosion has inhibited in Zn(Ⅱ) metal complex coated aluminum substrate than the bare aluminum substrate. In EIS the charge transfer resistance value (Rct) indicates the resistance to the corrosion. Higher corrosion resistance is indicated by a higher Rct value. Compared to the bare, unprotected substrate, aluminum substrate coated with Schiff base metal complex exhibited a noticeably higher Rct value. SEM images and the Impedance measurements conformed that pitting corrosion in chloride containing medium of aluminum substrates can be inhibited by coating of Schiff base Zn(Ⅱ) metal complex.
Iron corrosion inhibition using self-assembled layer of Schiff base ligand in saline and acidic media
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Gaveshika, E. G. J. K.; Weeraratne, A. D. K. I.; Narangoda, C. J.
Corrosion is an inevitable phenomenon and a naturally occurring process that can be defined as the deterioration of a metal surface through chemical or electrochemical interaction with its surrounding environment. Corrosion is an immense problem that significantly affects financial costs, environmental issues, and public safety. Numerous industries, including the automotive, construction, electronic, and other manufacturing sectors are used iron due to its low cost and excellent mechanical properties. Red brown iron oxide is formed, when iron is exposed to oxygen in the presence of moisture. Thus, corrosion prevention methods are very important. In this study, the Schiff base ligand was investigated as a corrosion inhibitor for iron surfaces in saline and acidic media as the main objective. Schiff base ligand was synthesized using salicylaldehyde and 4-chloroaniline. Synthesized Schiff base ligand was characterized using Thin Layer Chromatography (TLC), Fourier Transform Infrared Spectroscopy (FTIR) and UV-visible Spectroscopy. The FTIR spectrum displayed a significant peak at 1608 cm-1, indicating the C=N stretching vibration. The absence of the C=O peak in the salicylaldehyde and the N-H peak in the 4-chloroaniline, coupled with the appearance of a new band representing C=N, confirms the formation of the Schiff base ligand. Self-assembled layer is used as the coatings that prevent corrosion. Schiff base ligand form self-assembled layer on the iron surface. Self-assembled layer was examined using contact angle measurement and it showed 91 ͦ contact angle. This result suggests generation of hydrophobic film. Corrosion inhibition properties of Schiff base ligand on the iron substrate was studied through weight loss measurement, scanning electron microscope images (SEM) and ferroxyl indicator test. SEM analyses show, the blank iron substrate exhibited rough, corroded and irregular surface than coated iron substrates with Schiff base ligand after saline and acidic corrosion. The potassium ferricyanide was used for ferroxyl indicator test which can form a prussian blue complex in the presence of Fe2+ ions at the anode. No blue coloration was observed in the coated region with Schiff base ligand in both saline and acidic media. The mean corrosion rate and inhibition efficiency were calculated using weight loss measurement. The iron substrate coated with Schiff base ligand shows 51.68 % of corrosion inhibition efficiency in saline media and 49.89 % of corrosion inhibition efficiency in acidic media. In both acidic and saline media, blank iron surface shows the highest mean corrosion rate than coated iron substrate with Schiff base ligand. Therefore, Schiff base ligand acts as corrosion inhibitor in both acidic and saline media by making covalent bonds using electrons, and they chemisorb onto the iron surface. The developed corrosion inhibitor can be used for applications such as manufacturing anti-corrosion paint.