Synthesis and Evaluation of Novel Aromatic Azo Dyes as Efficient Corrosion Inhibitors for Carbon Steel

This study focuses on the innovative design and synthesis of five novel aromatic azo dyes N1-N5 from 4,4'-methylenedianiline using different coupling compounds (0.01 mol): 3,5-dihydroxytoluene, 4-hydroxy-3-methoxybenzaldehyde, 2-hydroxy-5-sulfobenzoic acid, 2-methylnaphthol, and 2,6-xylenol (1.24, 1.44, 1.01, 1.58, and 1.52 g, respectively). And the evaluation of their performance as corrosion inhibitors. The compounds N1–N5 were evaluated for their inhibitive effect on carbon steel in 0.5 M HCl solution. The weight-loss method was employed to monitor corrosion severity. The inhibitor concentrations tested were 0.003 and 0.005 M at 25°C, the results demonstrate that the synthesized azo dyes exhibit high inhibition efficiency by adsorbing onto the metal surface and forming a stable protective film, that way significantly reducing the rate of corrosion. The findings highlight the potential of these azo dyes as effective and promising corrosion inhibitors with improved performance compared to conventional inhibitors, among them, compound N3, which contains hydroxyl, carboxylic, and sulfonic acid groups, exhibited higher inhibition efficiency than the other compounds. The dyes were characterized by FTIR, mass spectrometry, 1H NMR, and 13C NMR, as well as by their physical properties, including color, melting point, and solubility.