I have an Ibanez SR500 which has a 'cosmo' black plating finish on all hardware. The finish on the bridge in particular is starting to discolour. It looks a bit like when aluminium starts to corode but without the white powder etc. Kind of white spots showing through. The bass is great to play and has a great tone. However, the discolouration on the bridge is really starting to detract from the look of the guitar. I have other basses a Jazz Mex (chrome) and a Yamaha BB604 (gold) and have no problems with these in terms of plating finish etc. Any suggestions or similar experiences...???