Cathodic protection is used all over the world to protect underground pipelines and tanks from corrosion. This is different than sacrificial anodes. In a nutshell, they apply a reverse voltage that is equal in magnitude but opposite in polarity to the natural corrosion emf that is set up between anodic and cathodic sites. It appears they are applying a similar scheme to protect car bodies from rusting. Back in the 80's there was similar (?) device sold called the Rust Buster.