palm rest pitting - corrosion

I have had my PBG4 1.67 almost 1 year now. I began experiencing pitting on the palm rest within 6 months after purchase and it has continued to progress despite my efforts to prevent it. The Apple Store tells me that it is cosmetic and they won't fix it. My arguement is that this is a known defect which is reported with some frequency. I am now 2 weeks away from my warranty lapsing. Does anyone know of any other solutions to get this repaired under warranty?

Thanks

PowerBook 15" G4/1.67, Superdrive, 1Gb Mac OS X (10.4.3) iMac 15" G4/800, PB WallStreet Sonnet G4/500