The metal brightwork on the body is made of aluminium rather than chrome (for environmental reasons).
Dirt or marks on the trim mouldings should be removed with an acid-free cleaning agent (do not use a chrome cleaner). Body polish is also unsuitable for use on trim mouldings. The intensive cleaning fluids often used before the car goes into a car wash may contain alkaline substances, which can cause dull or milky patches when they dry out.
Audi dealers carry stocks of cleaning products which have been tested for use on your vehicle and are not harmful to the environment.