Preprint Article Version 1 This version is not peer-reviewed

Corrosion Inhibition Mechanism and Efficiency Differentiation of Dihydroxybenzene Isomers Towards Aluminium Alloy 5754 in Alkaline Media

Version 1 : Received: 10 August 2019 / Approved: 12 August 2019 / Online: 12 August 2019 (03:58:57 CEST)

How to cite: Ryl, J.; Brodowski, M.; Kowalski, M.; Lipinska, W.; Niedzialkowski, P.; Wysocka, J. Corrosion Inhibition Mechanism and Efficiency Differentiation of Dihydroxybenzene Isomers Towards Aluminium Alloy 5754 in Alkaline Media. Preprints 2019, 2019080134 (doi: 10.20944/preprints201908.0134.v1). Ryl, J.; Brodowski, M.; Kowalski, M.; Lipinska, W.; Niedzialkowski, P.; Wysocka, J. Corrosion Inhibition Mechanism and Efficiency Differentiation of Dihydroxybenzene Isomers Towards Aluminium Alloy 5754 in Alkaline Media. Preprints 2019, 2019080134 (doi: 10.20944/preprints201908.0134.v1).

Abstract

Selection of efficient corrosion inhibitors requires detailed knowledge regarding interaction mechanism, which depends on the type and amount of functional groups within the inhibitor molecule. Position of functional groups between different isomers is often overlooked but not less important since factors like steric hinderance may significantly affect the adsorption mechanism. In this study we have presented how different dihydroxybenzene isomers interact with aluminium alloy 5754 surface, reducing its corrosion rate in bicarbonate buffer (pH = 11). We have shown the highest inhibition efficiency among tested compounds belongs to catechol at 10 mM concentration, although differences were moderate. Utilization of novel impedance approach to adsorption isotherm determination allowed to confirm that while resorcinol chemisorbs on aluminium surface, catechol and quinol follows ligand exchange model of adsorption. Unlike catechol and quinol, the protection mechanism of resorcinol is bound to interaction with insoluble aluminium corrosion products layer and was only found efficient at concentration of 100 mM (98.7%). The aforementioned studies were confirmed with scanning electron microscopy and x-ray photoelectron spectroscopy analyses. There is a significant increase of the corrosion resistance offered by catechol at 10 mM after 24 h exposure in electrolyte: from 63 to 98%, with only negligible changes in inhibitor efficiency observed for resorcinol at the same time. However, in the case of resorcinol a change in electrolyte color was observed. We have revealed that the differentiating factor is the keto-enol tautomerism. The NMR studies of resorcinol indicate the keto form in structure in presence of NaOH, while the chemical structure of catechol does not change significantly in alkaline environment.

Subject Areas

aluminium alloy; corrosion inhibitor; alkaline environment; impedance analysis; adsorption; dihydroxybenzene

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