I don't think you can solve that by just putting an import tax on aluminum. What about aluminum produced with cleaner energy than coal? Would you want to ask what energy source they used? Would you make it depend on the country of origin? What about for example cars? Would you also tax them for the aluminum content? Depending on the origin of that aluminum? If not it seems like you would create a disadvantage for US car manufacturers having to use the more expensive domestic or taxed imported aluminum. Or airplanes? Maybe it doesn't matter as much as I imagine because aluminum is always only part of the costs but I am convinced it would not be a trivial thing to tax dirty aluminum.