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Is there a chemical process to deposit an aluminum mirror onto a surface similar to the tollens reagent process for silver? I should add that any liquid process would satisfy my curiosity, it does not have to use water. Just anything to reduce the aluminum ions into metallic aluminum nano particles

I have searched and searched but have found very little on the subject. Thank you!

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    $\begingroup$ To get a silver mirtor you reduce an aqueous solution containing silver ions. Aluminum ions might be a little harder to reduce. $\endgroup$
    – Oscar Lanzi
    Commented Jan 23 at 18:33
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    $\begingroup$ Not possible in water environment. Aluminium is deposited from vacuum on clean glass and then protective layers are applied. $\endgroup$
    – Poutnik
    Commented Jan 23 at 19:13
  • $\begingroup$ @Poutnik It is to aluminize a mirror. The technique scales well to work on small reflectors and larger ones. $\endgroup$
    – Buttonwood
    Commented Jan 23 at 20:59
  • $\begingroup$ @David Dawkins A mirror with silver exposed as first surface (similar to the ones which are aluminized) looses quickly reflectance e.g., by the formation of silver sulfide. This is why silver coating typically is applied to the back and then covered by lacquer (an example). The aluminized mirrors can afford to have the reflective surface first, because the $\ce{Al2O3}$ layer which forms is practically transparent (at least in the range of visible light). But it contains pores (useful for embed dyes) which can trap dust. $\endgroup$
    – Buttonwood
    Commented Jan 23 at 21:05
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    $\begingroup$ @Buttonwood - i agree that one doesn't want to treat your optics like silverware, but when you want that extra percent or so of signal it is perfectly reasonable to use bare silver coated optics - it just makes the rest of the setup more complex. Silvered optics in a spectrometer are pretty easy since you just have to purge the box. $\endgroup$
    – Jon Custer
    Commented Feb 7 at 15:15

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Aluminum cannot be produced as a metal from and aqueous solution, because $\ce{Al}$ reacts chemically with water, producing $\ce{Al(OH)3 + H2}$, due to the rather negative value of the $\ce{Al}$ redox potential: $-1.70$ V. This reaction is suppressed on usual aluminum foils or objects, because, in air, metallic aluminum is spontaneously covered by a protective layer of aluminum oxide, which is thin, continuous, transparent, and protective against oxidation. As soon as this protective layer is locally removed by a scratch, new $\ce{Al2O3}$ is immediately synthesized in this scratch by the atmospheric oxygen of air.

This layer can be dismantled from the metal by dipping an aluminum object or foil in a solution of mercury chloride $\ce{HgCl2}$ for a couple of seconds. In contact of $\ce{HgCl2}$, the metallic aluminum reacts and produces some metallic mercury that makes an outer layer on aluminum amalgam. This amalgam prevents the formation of the protective and continuous layer of $\ce{Al2O3}$. As a consequence, the more or less amalgamated aluminum pieces react quickly with oxygen or water and produce in a couple of minutes long white filaments of $\ce{Al2O3}$. This strange phenomena lasts as long as some mercury is still remaining on the outer aluminum surface. Later on, mercury is eliminated from the surface so that the protective layer of $\ce{Al2O3}$ is regenerated. The corrosion stops.

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  • $\begingroup$ I should add, it does not necessarily have to use water as in tollens reagent. It can be any liquid. Just looking for a way aluminum ions into metallic aluminum nano particles for coating a surface $\endgroup$
    – David Dawkins
    Commented Jan 23 at 22:25

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