Abstract
The Schiff base compounds N,N ′ -bis(salicylidine)-4,4 ′ –diaminostilbene(SDS) and N,N ′ -bis(salicylidine)-4,4 ′ -diamino azobenzene(SDA) were synthesized, and their molecular structure was determined by FT-IR and 1H NMR. The corrosion inhibitions of Schiff base compounds on aluminum alloy 2024 in 1 M hydrochloric acid were evaluated by potentiodynamic polarization, impedance techniques, weight loss method, and scanning electron microscopic technique. The potentiodynamic polarization (PDP) studies revealed that SDS and SDA compounds acted predominantly as cathodic inhibitors. The electrochemical impedance spectroscopic (EIS) parameters confirmed the adsorption of SDS and SDA molecules over the surface of aluminum alloy 2024 alloy by forming an inhibitive layer. The weight loss studies showed that the inhibition efficiency of these compounds increases directly with concentration and decreases with an increase in solution temperature and immersion time. The thermodynamic parameters were calculated to investigate the mechanism of corrosion inhibition. The SDA was found to be more effective than SDS and followed the Langmuir adsorption isotherm model. The scanning electron microscopy (SEM) results revealed that the deterioration of the alloy surface is minimal in the presence of an inhibitor. Both Schiff base molecules exhibited superior corrosion inhibition for aluminum alloy 2024 alloy in HCl medium.
Highlights
Aluminum alloy 2024 is a high strength alloy that finds its utility in products that require a high strength-to-density ratio and good resistance to fatigue
The potentiodynamic polarization studies of AA2024 alloy were conducted in 1 M HCl at 303 ± 1 K in the absence and presence of SDS
The inhibition efficiencies obtained by potentiodynamic polarization, electrochemical impedance spectroscopy, and weight loss techniques of Schiff base inhibitors at all concentrations on the AA 2014 alloy in 1 M HCl are in good agreement
Summary
Aluminum alloy 2024 is a high strength alloy that finds its utility in products that require a high strength-to-density ratio and good resistance to fatigue. The higher percentage (3.8–4.9%) of copper in 2024 aluminum alloy greatly reduces its resistance to corrosion [3]. AA2024 alloy is very much susceptible to localized corrosive attack since the intermetallic compounds at the boundary get segregated. The localized pitting corrosion starts where the most predominant intermetallic inclusions exist. Al2MgCu is one such inclusion and reveals cathodic potential concerning the alloy matrix. Magnesium and aluminum get chemically and electrochemically dissolved from Al2MgCu particles at the beginning of corrosion which leads to dealloying enriching them with copper. The intermetallic precipitates become active anodes and cathodes, resulting in deep dealloying of the matrix [4]
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