Research Overview on Corrosion-Resistant Magnesium Alloys in China（2025 Aikerly）

Research on Corrosion-Resistant Magnesium Alloys in China: Progress, Distinctive Features, and Challenges

I. Core Research Progress in China

1. Field Exposure Testing in Marine Environments

• Distinctive Testing Platforms:

China has established rare long-term exposure bases in extreme tropical marine environments such as the South China Sea (Sanya, Nansha), featuring high salinity, humidity, and intense UV radiation. These facilities provide unique conditions for corrosion studies.

• Key Findings:

o For AZ31 magnesium alloy, the corrosion rate after one year of exposure in the South China Sea reaches tens of micrometers per year. The primary cause is Cl⁻ deposition and cyclic wet–dry exposure, which repeatedly fractures corrosion products (MDPI data).

o For the first time, full-scale component exposure tests have been conducted aboard oceanographic research vessels (e.g., the RV series), verifying the real-world degradation behavior of Mg–Y–Nd–Zn–Zr alloys under actual marine operating conditions.

2. Development and Optimization of Novel Alloy Systems

• Rare-Earth Strengthening Design:

The CAS research team developed the Mg–Y–Nd–Zn–Zr series. By optimizing Zn content (0.5–1.2 wt%), they significantly improved corrosion resistance in marine environments. Certain compositions exhibit over 40% lower corrosion rates than conventional AZ31 alloys.

• Low-Cost Modification Approaches:

For commercial alloys such as AZ31/AZ91, the addition of trace elements (Mn, Ca, or REs) — as seen in AZ31–0.05Mn — enables control of the Fe/Mn ratio (≤0.01), suppressing impurity-induced corrosion and achieving corrosion resistance comparable to that of high-purity Mg.

3. Innovations in Surface Treatment Technologies

• Engineering-Grade Coating Systems:

Development of micro-arc oxidation (MAO)–fluorination hybrid coatings has achieved over 3 years of effective protection in components deployed at South China Sea platforms.

• Biomedical Functionalization:

Through ion implantation of carboxyl/hydroxyl groups, the corrosion rate of biodegradable Mg implants can be precisely controlled in vivo, balancing mechanical support and degradation.

4. Application-Oriented Engineering Validation

• Marine Equipment:

In collaboration with China State Shipbuilding Corporation (CSSC), corrosion-resistant Mg alloys have been applied in sensor brackets and deep-sea buoys.

• Biomedical Applications:

Mg–Zn–Ca biodegradable bone screws have completed animal trials, achieving corrosion rates of 0.2–0.5 mm/year, suitable for clinical-grade degradation control.

II. Industrial Advantages and Technical Bottlenecks

Advantages:

• Resources and Industrial Chain:

Magnesium smelting capacities in Shanxi and Ningxia enable the production of high-purity Mg (Fe < 50 ppm), ensuring low impurity content for corrosion control.

• R&D Collaboration:

National programs such as the Ministry of Science and Technology’s “Corrosion-Resistant Magnesium Alloy Initiative” foster collaboration between universities, research institutes, and industry.

Bottlenecks:

• Insufficient Long-Term Reliability:

Laboratory accelerated corrosion tests (e.g., salt immersion) deviate from real-world South China Sea exposure results by 30–50%, limiting data accuracy for engineering design.

• Localized Corrosion Control Challenges:

Elemental segregation of Mn or REs in large castings triggers pitting corrosion, with acceptable yield rates below 60%.

• Cost Constraints:

Rare-earth additions increase alloy costs by 2–3 times, hindering mass adoption in automotive applications.

III. Case Study: AZ31–0.05Mn Alloy

Research conducted by Xi’an Jiaotong University exemplifies China’s low-cost, de-rare-earth corrosion-resistant alloy design approach.

Fig1 The corrosion resistance of the AZ31-0.05Mn alloy is comparable to that of high-purity magnesium (excerpted from a study by Xi’an Jiaotong University).

1. Value and Findings:

o Adding trace Mn (0.05 wt%) while maintaining Fe/Mn = 0.0075 reduces the corrosion rate of AZ31 to 0.25 mm/year, outperforming conventional AZ31 (≈0.8 mm/year).

o This provides a strong experimental reference for “de-rare-earth” corrosion resistance strategies.

2. Limitations:

o The data are derived mainly from short-term electrochemical tests, lacking field validation in China’s representative marine environments (e.g., Yellow Sea, South China Sea).

o The influence of Mn addition on mechanical properties (e.g., fatigue strength) has not been fully evaluated, limiting its immediate engineering applicability.

Conclusion

Leveraging abundant resources and strong engineering capabilities, China has developed a distinctive research path in corrosion-resistant magnesium alloys, emphasizing environmental field testing, low-cost alloy design, and marine-oriented applications.

However, long-term reliability and localized corrosion control remain critical challenges.

The AZ31–0.05Mn alloy from Xi’an Jiaotong University stands as a representative example of cost-efficient modification, yet further South China Sea exposure data are needed to validate its real-world durability and strengthen its engineering credibility.

References

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[15] GB/T 228.1–2021. Metallic materials — Tensile testing — Part 1: Method of test at room temperature [S].