The amount of biofouling - by barnacles and other organisms will depend on the water the object has gone through and in the oligotrophic (low productivity) water of the Southern India Ocean it will have been MUCH MUCH slower than in say the coastal North Atlantic. On the likely tracks the flaperon would mostly have floated through the marine equivalent of a desert.
http://oceanworld.tamu.edu/resources...production.jpg
The image linked to here shows the point, it is a global composite of phytoplankton production based on SEAWIFs satellite imagery where bright red is highest and indigo and violet lowest.
Nonetheless, there should be a succession of diatoms and other microorganisms on it, so it should be possible to reconstruct a history of where it has gone using a mix of taxonomic and geochemical data. The most useful aspect should be the first colonisers - which would give an indication of how far south the flaperon entered the water