FYI, one summer in high school I worked for a company that made plastic ornaments and novelty items many of which were "chrome" plated or partially plated. I worked in the plating area.
The way it was done was the parts were masked as necessary and were mounted on open frames so that the surface to be plated would not be obstructed. These frames were loaded into vacuum chambers with pieces of pure aluminum wire connected to electrical terminals. The chamber would be evacuated to a very low level. Once at the required vacuum level was reach a very high level of current was run through the alminum wire causing it to heat up and vaporize. The vaporized alminum would coat everything in the chamber. The very smooth surfaces of the plastic items would come out looking like they were chrome plated everything else had just a dullish aluminum look. The key was matching the size (length and gauge) of the wire to the total surface area you wanted coated. Too thick a coat and you lost the chrome look and to little and it would be transparent.