This is an electrochemical process that involves high voltage anodisation. Devices 
that have been treated will have a shiny violet color. You can see from the image below how small reservoirs are created.
Back in 2008 I did a post on another type of process used for coating devices again looking for the same outcome, less post operation infections.
Healionics Gets Angel Group Funding – Coatings for Implanted Medical Devices
Many of the new products from Zimmer may be sporting that light purple color soon. BD
OXFORD, England, Sep 03, 2010 (BUSINESS WIRE) -- Accentus Medical, a leading UK medical technology company that supplies advanced coatings and surface treatments to the medical device industry, announced today that it has signed a License and Services Agreement with Zimmer Holdings, Inc., a global market leader in musculoskeletal care. This agreement will enable the use of Accentus Medical's Agluna(R) anti-infective technology on a potentially broad range of Zimmer products.
Under the terms of the agreement, Zimmer will acquire exclusive global rights to utilize Agluna(R) for joint reconstruction and trauma products. In addition, the company will have an 18-month option to acquire additional exclusive rights for spinal devices, dental implants and sports medicine
products. As part of the agreement, there will be an initial period of further development of Agluna(R). Accentus and Zimmer will collaborate to secure regulatory approval for products treated with the Agluna(R) technology in both the E.U. and U.S. Financial details of the agreement were not disclosed.
Agluna(R) is a novel, patented surface modification technology applied to medical devices manufactured from titanium and its various alloys. The goal of the technology is to reduce infection rates following surgical procedures
Accentus Medical Signs Global Licence Agreement with Zimmer - MarketWatch