# Insights into the Corrosion Behavior of Pure Magnesium and Magnesium–Calcium Alloy (Mg-1.8 at.% Ca) in Thin-Film and Bulk Forms

## TL;DR

This study compares the corrosion behavior of pure magnesium and a magnesium-calcium alloy in bulk and thin-film forms, showing that thin-film Mg-1.8Ca has better corrosion resistance due to its microstructure.

## Contribution

The study reveals that thin-film Mg-1.8Ca alloy exhibits superior corrosion resistance due to its single-phase microstructure and stable surface film.

## Key findings

- Bulk Mg-1.8Ca alloy forms a Mg2Ca intermetallic phase, while thin-film Mg-1.8Ca remains single-phase.
- Thin-film Mg-1.8Ca shows significantly better corrosion resistance than its bulk counterpart.
- Microstructural control through manufacturing techniques can enhance the performance of Mg alloys.

## Abstract

This study investigates the microstructural and corrosion properties of pure magnesium (Mg) and Mg-1.8Ca (at.%) alloy in both bulk and thin-film forms. Microstructure investigations showed that the addition of calcium (Ca) to Mg resulted in significant differences in microstructures. The bulk pure Mg exhibited coarse and elongated α-Mg grains, which were refined by Ca addition, together with the formation of a Mg2Ca intermetallic phase distributed throughout the microstructure. In contrast, thin-film Mg-1.8Ca alloys displayed a refined single-phase microstructure with uniform nm-scale grains and no intermetallic formation. The electrochemical corrosion tests revealed that the bulk and thin-film pure Mg exhibited comparable corrosion rates, while a substantial difference between the corrosion resistance of bulk and thin-film Mg-1.8Ca (at.%) alloy was observed. The thin-film Mg-1.8Ca (at.%) alloy showed an exceptionally better corrosion resistance, attributed to the formation of a more stable surface film and the absence of a less noble Mg2Ca intermetallic phase, ensuring a single-phase microstructure. This study highlights the importance of different manufacturing techniques and microstructural control in improving the performance of Mg alloys for high-tech applications.