I use a stainless steel wire brush on the end of a long handle to scrub the element cover prior to bringing it to the boil. It works really well. Obviously I still get crap build up on it, and occasionally during a 90 minute boil it might cut out a bit towards the end which another quick scrub fixes. After the urn is emptied, a combination of an initial scrub with a plastic brush with some hot water, then boiling a bit of water and citric acid gets rid of it (this also removes that brown scaly shit with the aid of some steel wool). Thing comes up like new every time and no rust issues either.