Mechanism of corrosion inhibition of intermetallic Al2Cu in acidic solution

[Display omitted] •Thin layer of molybdenum oxides inhibits corrosion of intermetallic Al2Cu in acids.•The protective layer is spontaneously formed by heteropolyoxomolybdates.•Heteropolyoxomolybdate species do not inhibit corrosion of Al2Cu.•Heteropolyoxomolybdate stabilises aluminium oxide against...

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Bibliographic Details
Published in:Applied surface science 2021-06, Vol.551, p.149436, Article 149436
Main Authors: Kwolek, Przemysław, Wojnicki, Marek, Csapó, Edit
Format: Article
Language:English
Subjects:
Aluminium alloy
Corrosion
Heteropolyoxomolybdate
Intermetallics
Orthophosphoric acid
Phosphomolybdenum blue
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Summary:[Display omitted] •Thin layer of molybdenum oxides inhibits corrosion of intermetallic Al2Cu in acids.•The protective layer is spontaneously formed by heteropolyoxomolybdates.•Heteropolyoxomolybdate species do not inhibit corrosion of Al2Cu.•Heteropolyoxomolybdate stabilises aluminium oxide against dissolution. The objective of this work was to study the kinetics of phosphomolybdenum blue formation onto the surface of intermetallic Al2Cu in orthophosphoric acid solution. This was performed using UV–Vis spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical methods. The latter included measurement of open circuit potential, cyclic voltammograms, polarisation, and chronoamperometric curves as well as impedance spectra. It was shown that a stable form of phosphomolybdenum blue is formed via decomposition of an intermediate in the solution. However, neither phosphomolybdenum blue nor heteropolyoxomolybdate species behave as a corrosion inhibitor. A protective layer of molybdenum oxides formed immediately upon immersion of intermetallic in the corrosive environment, is responsible for corrosion inhibition.
ISSN:0169-4332
1873-5584
DOI:10.1016/j.apsusc.2021.149436