There are compositions of sheet metal (platings) where the base material is “impure” and is covered with a layer of pure aluminium. The surface is then chemically anodised to make it resistant to oxidation by contact with acid or other substances. Plated materials offer one solution for combining good performance with low cost.
Other ways of producing effective reflective sheet surfaces (factor > 92 %) are to use a layer of oxide and to vacuum metallise the surface. See the section on louvres and reflectors.
Various impressions can be made in the sheet surface to provide a structure that disperses or collects the light in a deliberate way.