Caravan Windows Discolouration

My Lunar caravan has windows which have a black “decoration” around their periphery. This black surround , on the front windows in particular has gone quite grey. The caravan is only 8 years old. My query, originally put on the Lunar Owners Technical Support Group was, what has caused this and how can it be rectified? I got no positive replies but think I have found the answer which may be of help to others. The grey appears to be oxidation of the top surface. I have found that this can be removed and a bright shiny black surface restored. I tried various products but have found that Brasso works the best. It takes a lot of rubbing but does the job eventually. T-Cut was a close second choice.

I hope this helps if anyone else has a similar problem.