Insights into the Corrosion Behavior of Mg-1sc Alloy in Varied Corrosive Environments: Comparative Analysis of Three Distinct Application Media

Abstract

This study explored the effects of different corrosive media on the corrosion behavior of Mg alloys by preparing three solutions: 3.5 wt.% NaCl, 0.1 M Na₂SO₄ and 30 vol.% ethylene glycol, simulating relevant service conditions. The Mg-1Sc alloy was selected for investigation due to the high solubility of scandium in Mg and the unique properties of its corrosion products. Microstructural analysis showed that Mg-1Sc contains a small amount of Mg3Sc second phase particles with a more positive potential than the Mg matrix, which can accelerate corrosion as a cathode in galvanic corrosion. Hydrogen evolution and electrochemical experiments revealed the corrosion rates of Mg-1Sc in the three media as follows: 30 vol.% ethylene glycol < 0.1 M Na₂SO₄ < 3.5 wt.% NaCl. The high corrosion rate in the 3.5 wt.% NaCl solution is attributed to small chloride ions (Cl⁻) that penetrate the loose and porous Mg(OH)2 corrosion products, causing severe pitting and localized corrosion. The sulfate ions (SO₄²⁻) in the 0.1 M Na₂SO₄ solution can also promote the formation of MgSO4, which somewhat offer a protective effect, thereby reducing the corrosion rate. In contrast, the 30% ethylene glycol solution, lacking significant corrosive ions, resulted in more uniform corrosion and the lowest corrosion rate.

Keywords: Mg-Sc alloy, corrosion behavior, NaCl, Na₂SO₄, ethylene glycol