This study investigates the fabrication of a Cu-Mn-Al alloy coating on 27SiMn steel using Cold Metal Transfer (CMT) technology with an innovative Ar-B(OCH₃)₃ mixed shielding gas, focusing on the effect of the gas flow rate (5–20 L/min). The addition of B(OCH₃)₃ was found to significantly enhance process stability by improving molten pool wettability, resulting in a wider cladding layer (6.565 mm) and smaller wetting angles compared to pure Ar. Macro-morphology analysis identified 10 L/min as the optimal flow rate for achieving a uniform and defect-free coating, while deviations led to oxidation (at low flow) or spatter and turbulence (at high flow). Microstructural characterization revealed that the flow rate critically governs phase evolution, with the primary κI phase transforming from dendritic/granular to petal-like/rod-like morphologies. At higher flow rates (≥15 L/min), increased stirring promoted Fe dilution from the substrate, leading to the formation of Fe-rich intermetallic compounds and distinct spherical Fe phases. Consequently, the cladding layer obtained at 10 L/min exhibited balanced and superior properties, achieving a maximum shear strength of 303.22 MPa and optimal corrosion resistance with a minimum corrosion rate of 0.02935 mm/y. All shear fractures occurred within the cladding layer, demonstrating superior interfacial bonding strength and ductile fracture characteristics. This work provides a systematic guideline for optimizing shielding gas parameters in the CMT cladding of high-performance Cu-Mn-Al alloy coatings.

Magnesium–lithium alloys, currently the lightest metallic structural materials, exhibit exceptional specific strength, superior damping capacity, and remarkable electromagnetic shielding properties. These characteristics endow them with significant potential for engineering applications in automotive, aerospace, satellite, and military industries. However, their poor corrosion resistance severely restricts practical implementation. This review systematically examines recent advances in surface engineering techniques for magnesium–lithium alloys, with a focus on corrosion protection strategies. Key approaches are critically analyzed, including chemical conversion coatings, electroless plating, anodization, and advanced coating technologies. Furthermore, emerging hybrid methods combining multiple surface treatments are highlighted. Finally, future research directions are proposed to address existing challenges in surface protection of magnesium–lithium alloys.

Magnesium-lithium alloys, currently the lightest metallic structural materials, exhibit exceptional specific strength, superior damping capacity, and remarkable electromagnetic shielding properties. These characteristics endow them with significant potential for engineering applications in automotive, aerospace, satellite, and military industries. However, their poor corrosion resistance severely restricts practical implementation. This review systematically examines recent advances in surface engineering techniques for magnesium-lithium alloys, with a focus on corrosion protection strategies. Key approaches are critically analyzed, including chemical conversion coatings, electroless plating, anodization, and advanced coating technologies. Furthermore, emerging hybrid methods combining multiple surface treatments are highlighted. Finally, future research directions are proposed to address existing challenges in surface protection of magnesium-lithium alloys.