base metal + (nickle)+bright nickle+ chrome. The chrome could be considered the "clear coat" over the bright nickle. The chrome plating is hard and can be removed to expose the nickle under it. Older types of abrasive chrome cleaners exposed the nickle underneath and covered the shiny nickle with automotive wax. Corrosion of the base ferrous metal is usually red rust that bleeds through the micro-porous chrome coating or between the micro-fractured chrome cells.
sorry about the wordy explanation.