[Milsurplus] Question - how to remove oxidized aluminum or steel safely leaving markings?

[john p hutchins]

Group -

I have seen some well refurbished vintage radios with well polished 
chassis and parts.  How to safely remove the old oxidized aluminum or 
steel  with out removing the markings paint.  Any one find a site or 
posses any techniques and or methods to accomplish  the cleaning with 
out taking off the chassis or part paint markings, stamps?

Thanks
Hutch