Interesting reaction with water to release H2. Not sure if this is a catalytic reaction and therefore could be used indefinitely to release H2, but I can see why some are trying it as an alternative fuel.
Gallium amalgamates with Al it much as mercury amalgamates with gold or silver. Gallium penetrates the crystal structure dissolving the aluminum, too.
Gallium has the unusual property, unlike mercury, of being able to penetrate the oxide film on aluminum and so attacks it much more readily.
The result is an alloy of gallium and aluminum.
As seen in the phase diagram below, Aluminum has a huge solubility in Galium in the ambient temperature.
The Galluim penetrates the oxide laser normally protecting Al showing the usually-hidden high natural reactivity of metallic aluminum .
Activated Al can then be oxidized with water.
Oxygen in H2O will oxidize the dissolved Aluminum and release H2 as follows:
Al + 3H2O > Al(OH)3 + 3/2H2 ^ what remains later is liquid gallium and water with Al2O3 particles.
See "Activation of Aluminum Metal and Its Reaction with Water":
https://www.researchgate.net/publication/257357858_Activation_of_Aluminum_Metal_and_Its_Reaction_with_Water
Gallium is interesting elemental stuff and many uses have been found for it. "It shares the higher-density liquid state with a short list of other materials that includes water, silicon, germanium, antimony, bismuth, and plutonium.
Gallium attacks most other metals by diffusing into the metal lattice. For example, it diffuses into the grain boundaries of aluminum-zinc alloys and steel, making them very brittle and it easily alloys with many metals"
See:
https://en.wikipedia.org/wiki/Gallium
Example: The interesting property interplays of Gallium/Plutonium alloy.
Plutonium is without question the most complex and interesting of all metals.
Gallium is used to stabilize plutonium's crystal structure.
Plutonium has a large number of very peculiar properties, amongst them:
Pu has the lowest thermal conductivity of any metal,
Pu's electrical conductivity is lower than any metal.
Pu is the most viscous liquid metal known.
Pu undergoes the most extreme and bizarre density changes with temperature of any known element.
Plutonium has six distinct phases (crystal structures) in solid form, more than any other element, actually there is a seventh that exists under certain conditions but...
At room temperature pure plutonium exhibits a crystal structure that is termed the "alpha phase". In this form plutonium is at its maximum density 19.84 at 20 C. The atoms in the alpha phase are essentially covalently bonded (as opposed to metallically bonded), giving it physical properties more nearly like a mineral than a metal.
Delta phase plutonium, density of about 15.9, has normal metallic properties, including excellent ductility. The delta phase has strength and malleability similar to aluminum, which makes forming and machining straightforward, although interestingly, it shrinks when heated rather than expands.
Plutonium can be stabilized in the delta phase at room temperature by alloying it with certain trivalent atoms such as Gallium, however, when stabilized, the delta phase still collapses easily, a pressure of a few kilobars is sufficient to make it revert to the alpha phase.
Plutonium is normally stabilized in the delta phase by alloying it with 3-3.5 molar% gallium (0.9-1.0% by weight). This alloy is stable from at least -75 to 475 degrees C. The stabilization prevents low temperature phase changes from occurring after fabrication, casting and machining, that would ruin the precisely made components. Gallium stabilized plutonium has an almost zero coefficient of expansion which makes casting easier and the gallium also reduces the susceptibility to corrosion of plutonium
Problem solved w. Gallium, without which...