How do I polish my knife blade back to original shine?

If by corroded you mean rusted, there is not much that you can do outside of using progressively finer grit of wet/dry sandpaper and a buffer wheel with metal polish, but if the rust is bad enough even this won't bring the blade back to it's original condition. However, if the blade is just corroded i.e., discolored try the metal polish called FLITZ, Wal Mart should have it on the household cleanser isle, try this first no matter what. I have used FLITZ on some of my knives that needed it and I am very satisfied with the end results.

I use this stuff called Nevr Dull. It is amazing. It comes in a tin can and it is basically a can stuffed with some kind of wool wadding that is imbedded with a compound for cleaning and polishing. It smells a bit like mineral spirits. I maintain aquariums for a living and find a good pocket knife indispensible. The problem is, the thing is always getting exposed to saltwater and gets rusty very quickly. I clean and polish it weekly with this stuff after sharpening and oiling with 3in1 oil. Good as new everytime in no time.

don't know the extent of you corrosion but if it is just on the surface you can go to a truck stop or hobby lobby or an automotive store or maybe lowes and get some jewelers rouge to use. they will have different color buffing wheels like yellow or red or white etc. the color denotes the stiffness for your cuts to bring the shine back, the jewelers rouge also comes in different colors, green red, black, white etc. and these co;ors also tell you basically the abrasiveness of the rouge. the rouge should come with a guide. if it's more than surface rust you may have to use some emery cloth to get a rough-in shine and then switch to the polishing wheels and rouge.

Use some extremely fine Wet & Dry paper, or some wire wool, like the stuff that you scrub a pot with.

If that doesn't work to your satisfaction you may need to get it replated.

you can use either a very fine sandpaper or steel wool, or you can get something like silver polish

steel wool