Corrosion behaviour of the Al-2.1–Mg-1.8–Si alloy in chloride solution

Abstract

The corrosion behaviours of Al-Mg-Si alloys were studied in different Cl − concentrations by means of scanning electron microscopy, transmission electron microscopy and electrochemical experiments. The results show that the corrosion behaviours of Al-Mg-Si alloys are closely related to the Cl − concentration. With an increase in Cl − concentration, the corrosion rate increases sharply by facilitating the process of chemical and electrochemical reactions. In 2.0 wt.% NaCl solution, slight pitting corrosion occurred around the MgSi phase, but corrosion trenching was not found around the Fe-Mn-Si phase. In 3.5 wt.% NaCl solution, the alloy appeared localized corrosion dominated by intergranular corrosion attack. In 5.0 wt.% NaCl solution, the alloy presented serious overall corrosion, and the passivation platform of the polarization was not obvious. Furthermore, an appropriate corrosion mechanism according to polarization and electrochemical impedance spectroscopy was proposed for the Al-Mg-Si alloy in NaCl solution. In addition, the corrosion rate influenced by different Cl − concentrations was discussed in detail.

Anticorrosive PEO coatings on metallic cast heat enhancers for thermal energy storage

“…Alloys were tested, among others, in the mix of chloride alts: MgCl 2 , NaCl, and CaCl 2 . The corrosion reaction of silicon – magnesium – aluminium alloy in chloride salt solutions was as well described by Zheng et al [13]. According to their work, it is believed that the corrosion process starts at grain boundaries, which are not covered with a protective, natural passivation layer.…”

“…These findings imply that both cations and anions (respectively Mg 2+ and Cl − ) participate in the reaction with Al substrate and contribute to the formation of new phases. In [13], Zheng et al performed the corrosion test for aluminium alloy containing 1.8% of silicon in chloride solutions – water solutions of NaCl in quantities: 3.5%, 2% and 5%, by weight. Corrosion in the form of pitting was observed on the parts of the sample not covered with a natural oxide layer – grain boundaries.…”

“…Nevertheless, this natural coating does not withstand the harmful environment of acidic or alkaline pH [12] in which it dissolves, exposing the material beneath. Phase change materials based on chloride hydrates are extremely detrimental to aluminium and its alloys [13], especially for the ones with Si as the main alloying compound. Such alloys, called silumins, suffer from localised corrosion, which rate is notably affected by the Si content [14,15].…”

Investigation of corrosion characteristics of Cu-10Ni-1.2Fe-xMn (x = 0.53, 0.87, 1.19) alloy in 3.5% NaCl solution

“…The corrosion rate is calculated by the following formula: where A represents the molar mass, n represents the number of charge transfers of the reactants, ρ is the density of the alloy, and F is the Faraday constant (value 26.8 A h). 23 Obviously, as the amount of Mn added increases, the self-corrosion potential moves in a more positive direction, which shows that as the amount of Mn increases, the corrosion tendency becomes worse. As show in Table 3 , the I corr of 0.87Mn alloy is lower than that of other samples, which mean that 0.87Mn alloy has better corrosion resistance.…”