Lightweight magnesium-based vapor–liquid two-phase heat transfer device with phytic acid decoration

Aluminum-based phase-change heat transfer devices offer lightweight thermal management, but further weight reduction requires alternatives. Magnesium has been proposed, yet its chemical reactivity has hindered practical implementation. Here, we propose a surface modification strategy utilizing phytic acid to generate a chelating protective coating on magnesium surfaces. This coating suppresses adverse reactions between the packaging material and working medium while introducing hydrophilic groups and a micro-crack structure, with Mg-O-P coordination bonding confirmed by FTIR. Under boiling conditions, the 3 wt% PA coating thickness stabilizes at ∼3.65 μm after 48 h. A comparable trend under static immersion indicates that dissolution of excess physisorbed PA, rather than hydrodynamic stress, drives the thinning. Capillary rise height in ethanol increases from 57 mm to 75 mm after 3 wt% PA modification. The 3.04 g device achieves a maximum effective thermal conductivity of 1367 ± 65 W/(m·K) and thermal resistance of 3.18 ± 0.15 K/W, with no degradation over 100 cycles. Performance-per-mass comparison against literature devices confirms that the Mg device occupies a unique lightweight position among two-phase heat transfer systems. These results establish PA-modified magnesium as a promising lightweight packaging material for phase-change thermal management, particularly in aerospace applications.