Abstract
The study of protective film formation on Mg alloys by exposure to sodium selenite solutions was conducted. Anodic polarization studies, electrochemical impedance spectroscopy studies, morphological analysis, and Energy-dispersive X-ray spectroscopy were performed on AZ31 Mg alloy after coating treatment in different concentrations of sodium selenite. The corrosion resistance was improved by around 5 times compared with control. Improved resistance to localized corrosion was observed in the coatings treated by 5 mM or 10 mM sodium selenite. The protection mechanism was ascribed to the transformation of selenite to insoluble selenium, the formation of insoluble MgSeO3 hydrate, and polymerization of amorphous selenium.
Highlights
Magnesium alloys have attracted attention due to its high strength and low density [1,2,3]. have been widely used in a number of industrial sectors such as biomedical devices, the automotive industry, aerospace components, and in the field of electronics [1,4,5,6,7].Mg is a very active metal and vulnerable to corrosion attacks when exposed to aqueous environments or humid air [1,8,9]
After immersion in different coating baths with different selenite concentrations, a uniform pale grey film was formed on AZ31
Corrosion current density ues were determined by extrapolation of the linear portion of the log-based cathodic povalues were determined by extrapolation of the linear portion of the log-based cathodic larization curves to the intersection with corrosion potential values [14]
Summary
Magnesium alloys have attracted attention due to its high strength and low density [1,2,3]. have been widely used in a number of industrial sectors such as biomedical devices, the automotive industry, aerospace components, and in the field of electronics [1,4,5,6,7].Mg is a very active metal and vulnerable to corrosion attacks when exposed to aqueous environments or humid air [1,8,9]. A number of approaches like alloying, coating, surface modification, and chemical inhibition have been addressed in the R&D community recently [1,2,10,11,12,13,14,15,16,17,18]. Among these approaches, the coating provides corrosion protection without affecting mechanical properties the way alloying approaches do. The additional hydrolyzation and polymerization of Cr3+ will contribute to a Cr-hydroxide inorganic polymer network that results in forming a film that increases corrosion resistance [20,22,23]
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