[G6Tanuki]

There's no real easy answer to the cosmetic part apart from getting the chassis replated!

To preserve the chassis from ongoing corrosion in the absence of the plating; keep it in an environment where the relatibe-humidity is low [I run a dehumidifier in my office/workshop - it keeps R.H. below 50%] and when the radio is not in regular use consider using some of the brown "vapour phase corrosion inhibitor" paper beloved of engineering-workshops for decades when they need to store machined componets, cutting-tools etc. A quick Google for "VCI Paper" will show you the way.