There are two main reasons for polishing metal alloys on aircraft:
- To ensure a mirror finish for these parts which can transform the whole look of an aircraft.
- To prevent corrosion.
These alloys are designed to withstand extreme conditions. However, they are exposed to abrasion, chemicals in de-icing and cleaning products, pollution, combustion gases and even acid rain in some parts of the world, particularly in Asia.
All of these tarnish the metal and can weaken it over successive flights. Corrosion is exacerbated as these caustic substances penetrate the metal.
Metal polishing also helps increase lift-to-drag ratio and can reduce fuel consumption.