The contribution of hydrogen evolution processes during corrosion of aluminium and aluminium alloys investigated by potentiodynamic polarisation coupled with real-time hydrogen measurement

Abstract

Water reduction, which leads to the evolution of hydrogen, is a key cathodic process for corrosion of many metals of technological interest such as magnesium, aluminium, and zinc; and its understanding is critical for design of new alloys or protective treatments. In this work, real-time hydrogen evolution measurement was coupled with potentiodynamic measurements on high-purity aluminium and AA2024-T3 aluminium alloy. The results show that both materials exhibit superfluous hydrogen evolution during anodic polarisation and that the presence of cathodically active alloying elements enhances hydrogen evolution. Furthermore, it was observed for the first time that superfluous hydrogen evolution also occurs during cathodic polarisation. Both the anodic and cathodic behaviours can be rationalised by a model assuming that superfluous hydrogen evolution occurs locally where the naturally formed oxide is disrupted. Specifically, during anodic polarisation, oxide disruption is due to the combined presence of chloride ions and acidification, whereas during cathodic polarisation, such disruption is due to alkalinisation. Furthermore, the presence of cathodically active alloying elements enhances superfluous hydrogen evolution in response to either anodic or cathodic polarisation, and results in 'cathodic activation' of the dissolved regions.

Respirometric In-Situ Methods for Real-Time Monitoring of Corrosion Rates: Part I. Atmospheric Corrosion

“…Acidification and high chloride concentration maintain depassivation and lead to direct contact of unprotected Al with water. 29 This results in vigorous H2 evolution similar to anomalous H2 evolution generated locally at dissolving Mg sites. 29,38 Further monitoring revealed an increasing HER rate and a decrease in ORR rate, while the total corrosion NaCl.…”

“…29 This results in vigorous H2 evolution similar to anomalous H2 evolution generated locally at dissolving Mg sites. 29,38 Further monitoring revealed an increasing HER rate and a decrease in ORR rate, while the total corrosion NaCl. Again a very good correlation of the pressure sensor charge with the optical O2 sensor charge was found.…”

Qualitative use of potentiodynamic polarization and anodic hydrogen evolution in the assessment of corrosion susceptibility in AA2198‐T851 Al–Cu–Li alloy

“…The knowledge of the pH variation is important in the understanding of the anodic hydrogen evolution (AHE) mechanism in Al and its alloys. Most recently, Curioni et al proposed that one of or a combination of low pH, high chloride concentration, and a remote current source is essential for AHE.…”

Influence of the shape of hydrogen-containing inclusions on the intergranular corrosion process of the Al – Si alloy system

“…Hydrogen emission occurs locally where the naturally formed oxide is disrupted. The presence of catho dically active alloying elements enhances superfluous hydrogen emission response to either anodic or cathodic polarisation and results in "cathodic activation" of the dissolved regions during corrosion process [3].…”

“…A s it is known, high-performance magnetically hard materials (MHM) based on Nd -Fe -В alloy are characterized by low resistance to corrosion [1][2]. It is one of their main imperfections along with poor temperature stability [3][4]. Therefore, vari-ous anticorrosive coats are used to elongate service life of permanent magnets (PM) made of the above mentioned materials [5][6].…”