"Yes weaker. It weakens the alloy which in turn can lead to cracks and failures. Like stated above, leask around the bead and so on. I am not saying it happens to every set, but it does happen."
But how? This makes no sense. They are not heated up in any except during the initial polishing stage. They are then dipped in copper to fill in any pits and to give the nickle something to stick to. Depending on how pitted, they may only stay in the copper for a few minutes. They would be polished again. Then they would go to nickle for a few minutes then back to polish. Then into the chrome bath and then back to polishing. Aluminum wheels are chrome plated everyday. The bead problem is the chrome peals, not allowing a good seal for the tire.
Anyway, call Chromemasters or Advanced Plating, both are in Nashville,TN. I have used both for plating and will do you an excellent job. Advanced will be quite a bit more expensive than ChromeMasters. If you have any concerns about the chrome weakening the aluminum, these guys will know.
As for powdercoating aluminum, it is generally not a good idea to do on a structural piece. You can do it if the person uses a low heat powder. If you heat aluminum up to 425 degrees, the normal curing temp for powders, it changes the moleculer structure and makes the material weak. Which in turn could cause cracks and lead to a complete failure of the part.