Painting corroded 9V battery contacts with vinegar I have an old radio with corroded 9V battery contacts, probably from a battery that corroded though I don't know.

I wanted to clean up the contacts with 5% vinegar since that works with pennies, but this is not something I can dunk in a small container since it is attached (with a very short wire) to the radio).

So I want to thicken vinegar to a gel, and not change the pH.  I would rather do this slowly, I can leave the solution on the contact for as long as necessary.

A high school chemistry teacher suggested vaseline as a thickener.  I just wanted to get a second opinion that vaseline will not somehow cause a problem?  Glycerin was also mentioned.  Could either react in any way with the metal electrode?

If I use either, presumably the acididy will decrease by dilution with the thickener.  Is this linear, or does the thickening of the solution have any other affect on acids?  I can try treating the surface for a few hours, or a day, then how could I get it off?  My guess is a cotton swap with water and detergent to clean off the gel?

I am not 100% sure what the surface of the contact is, it could be a nickel alloy, it certainly is a formerly shiny silvery metal, now somewhat dulled with green raised bumps on it from some former chemical reaction.

If you think I should just apply vinegar, or anything else for that matter, with a cotton swab I could do that, I just want to be able to apply something and clean up the surface with a minimum of effort.
Using vinegar, petroleum jelly, or glycerol to clean the contacts would leave some residue.  Vinegar might dissolve it somewhat more quickly than water, but you have to be sure you get all the vinegar off the contact, or it could cause more corrosion.  Petroleum jelly - I think someone was kidding you.  Vinegar &amp; petroleum jelly don't mix.  

Much easier: use a small piece of emery paper or steel wool to grind the deposit off.  Keep sanding until the metal is shiny.  Use a damp rag to remove the powder.  Don't let the ground-off powder fall into the circuitry.  

Edit:  added steel wool.