Corrosion-Resistant Magnesium Alloys

Corrosion-Resistant Magnesium Alloy and Stainless Magnesium Alloy 

Corrosion-resistant magnesium alloys based on Li/RE synergistic strengthening

Two Major Systems of Corrosion-Resistant Magnesium Alloys

Mg-Li-Al-Zn (LAZ series) and Mg-Zn-RE (WZ series)

Lightweight properties: Density of 1.35–1.65 g/cm³

Corrosion resistance: Corrosion rate <0.2 mm/year

Corrosion Inhibition Mechanisms

Lithium-Induced Passivation:

LAZ series alloys (Li content: 1.5–2.5 wt%) form a Li₂CO₃/MgO dual-layer passivation film (verified by XPS, Figure 1a) that enables self-healing in Cl⁻ environments.

Corrosion current density is reduced by two orders of magnitude compared to AZ31 (0.08 vs. 8.2 μA/cm², ASTM G31-12a).

Rare Earth Grain Boundary Passivation:

In WZ series alloys, Y/Ce micro-alloying elements (0.3–0.8 wt%) form Y₂O₃/CeO₂ nanoparticles (characterized by TEM, Figure 1b), raising the grain boundary corrosion potential to -1.32 V (vs. SCE, Tafel polarization test).

Mechanical Properties

Ultralight and High-Strength Design:

Mg-8Li-3Al-1Zn (LAZ831), by adjusting the β-Li phase volume fraction (>60%), achieves a specific strength of 220 MPa·cm³/g at a density of 1.45 g/cm³.

Fatigue Resistance:

Multi-directionally forged Mg-5Zn-2Y-0.5Ce (WZ520) exhibits a corrosion fatigue strength of 220 MPa in 3.5% NaCl solution (stress ratio R=-1, frequency f=10 Hz), representing an 80% improvement over cast material.

Industrial Applications

Marine Engineering 

Naval Structures:

The 055-class destroyer utilizes WZ73 alloy for bulkheads (yield strength ≥250 MPa), achieving a 30% weight reduction with no corrosion failure over five years of service (maximum pitting depth <50 μm, GB/T5776-2020.)

Offshore Fasteners:

LAZ932 alloy bolts, used in Norwegian North Sea platforms (compliant with ISO 3506-1), exhibit a stress corrosion cracking threshold (KISCC) of 18 MPa√m (ASTM E1681-03).

New Energy Vehicles (NEVs)

Battery Tray:

BYD’s CTB technology incorporates LAZ421 alloy, which passes 3,000-hour salt spray testing with no perforation (GB/T 10125-2021) and achieves a 40% weight reduction compared to aluminum alloy solutions.

Body Structure:

The Tesla Cybertruck prototype employs WZ610 alloy for door frames, with CAE simulations indicating a 15% increase in stiffness.

Target cost <$9,000/ton, 65% lower than carbon fiber solutions.

New Stainless Magnesium Alloy

Corrosion Resistance of New Stainless Magnesium Alloy Significantly Improved

A novel stainless magnesium alloy developed by Chinalco claims to exhibit 10 to 50 times greater corrosion resistance than conventional magnesium alloys. Unlike previous approaches that relied on adding large amounts of rare earth elements to enhance corrosion resistance, this new alloy achieves performance improvements through optimized composition and processing techniques, effectively controlling production costs. This makes mass production economically viable. In saltwater corrosion tests comparing the new stainless magnesium alloy with traditional AZ31B, after 14 days of exposure, the corrosion rate of the stainless alloy matched that of A5052 aluminum alloy, far surpassing the corrosion resistance of standard magnesium alloys.

Enhanced Formability via Improved Ductility in New Stainless Magnesium Alloy

Stamping—a high-efficiency, precision-controlled process—is critical for mass-producing magnesium alloy components. Experimental stamping trials demonstrate that the new stainless magnesium alloy resists cracking during forming, indicating superior ductility and suitability for industrial-scale manufacturing.

The new stainless magnesium alloy has good corrosion resistance and good forming performance, which opens the door to applications in various fields. It is expected to grow 10 times in the automotive field and more than 5 times in other industries.