Brasso?

When I was in the Coast Guard our dungarees (work uniform) included a woven belt with a brass buckle.  Once I was out of boot camp, nobody cared how shiny the buckle was, but in boot camp we had to keep the buckle shiny.  We used a product called Brasso.  I don't know if it is still available or sold under the same name (this was 1964).

If the product is still available, try putting it on a cloth and put the cloth across the tracks.  Run one end of the locomotive onto the cloth and then hold it in place while you allow the locomotive wheels to spin on the cloth where the Brasso is.  Once the wheels are cleaned at that end, swap ends and repeat.

No to Brasso. Yes to Mineral Spirits, Graphite, & Nickel Silver

Dear Jim, Russ,

Russ, I'd strongly reccomend against Brasso. Previous discussions here on MRH
https://model-railroad-hobbyist.com/node/16333

suggest that Brasso is likely to provoke further corrosion on common wheel materials. This is particularly evident on Athearn sintered-Iron wheels (Blue box diesel era), and is caused by water and ammonia content within the Brasso formulation.

EG An Athearn sintered-iron wheel from a HO SD40-2, stored for 3 months after being "cleaned" with Brasso...
...Thankfully a decent polish with Mothers Mag Wheel Polish reversed the damage and returned the wheelsets to "better than new" condition...

Jim, if you're looking for "what to clean wheels with",
I'd reccomend going with Mineral Spirits, as discussed and confirmed appropriate for rail cleaning
https://model-railroad-hobbyist.com/magazine/mrh2019-05/publishers-musings

Once both rails and wheels are clean, add graphite for long-lasting contact performance.
https://model-railroad-hobbyist.com/magazine/mrh-2015-05-may/fight-dirty-rails-with-graphite
/> https://model-railroad-hobbyist.com/node/17181

Now, from your description, it sounds awfully like you may have some older models,
lower-spec models (Tyco, etc?),
or plastic locos with "Nickel silver plated" wheels where the plating has worn off, in play?
(1st Gen Bachmann Spectrum locos come to mind, 44 and 70 tonners?)

Such models do indeed have Brass or other "no soo easy to keep clean and conductive" as the core material of the wheels, with predictably annoying performance results. Graphite is a good "patch-over" measure, which is surprisingly long-wearing and performance improving. However, for proper reliable "fixing", getting back to a solid Nickel-silver wheel, or at least a decent-thickness Nickel-silver plating on the wheels, is the best move.

Depending on the actual model in question:

- North West Shortline have replacement Nickel-silver wheels for many HO diesels. These are well-known, well-respected, and typically a "plug-in" fit.
https://nwsl.com/collections/ho-hon3-scale

- If the model is rare, unusual, or not covered by the NWSL range,
you may be better-off seeking someone reliable who will take the existing wheelsets,
and do nickel-silver plating on them.
https://www.shayfixer.com/thenickelplater.htm 

I hope this helps...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

The O.P. was asking about cleaning corrosion off brass wheels.

I was not addressing the issue of Athearn sintered iron wheels or any other wheels except corroded brass wheels

Cleaning wheels

Still the same process.  If you don't want to take the trucks apart then I suggest getting some "handiwipes" cleaning cloths.  Two products I have used and they both work well are Mothers Mag and Aluminium Polish and Flitz Polish.  Use sparingly is the key but set up a short track on a board so you can tack the wipes on one end.  Apply the polish of choice where the wheels will make contact with the polish on the cloth and slowly apply track power. (One set of trucks must be on bare track)  Hold the loco untill the wheels are bright and shiney!  Clean with mineral spirits or some other solvent. (CRC 2-26 Oil works great).  Also read  https://forum.mrhmag.com/post/polish-those-athearn-wheels-12195538

And Video>

Cleaning Wheels

Absolutely, 100%, mineral spirits. Put some on the tread and let it sit for awhile. Then rub it off. If you have some particularly stubborn spots, try it again, until clean. Avoid using an abrasive tool, unless you are very careful and only if the tread has mineral spirits on it, when doing so. Never use abrasives if the tread is dry. Glenn

Its difficult to tell exactly

Its difficult to tell exactly what you have with no pic . If they are older Athearn "iron" wheels , replace them with Northwest Short line Nickel Silvers or other suitable NS wheels. You want to avoid abrasives at all cost on nickel silver wheels , the plating is usually only a few micro inches thick. If have to get aggressive with it use wood sticks or brown paper / news print paper , The harshest thing I would use is baking soda , you can put it on a dry rag and rub if needed.

If the wheels are brass and its a quality locomotive and you can't find suitable replacement NS wheels I would consider electroplating them , there are plenty of youtube videos to show you how and you can get just about everything you need from the grocery store.You can probably use left over bits of NS rail to make the solution. 

Great Feedback

Thanks everyone for the feedback. I will try some of your suggestions. I think the wheels look like brass, because they look tarnished. The Locomotives that I am currently working on are Atlas Rock Island. I have tried to take the truck apart as far as I dare to, without doing any damage. I do not know what I may tear up if I go any farther. I am trying to find videos to help me on the truck disassemble. Here Is a picture of the truck.

Jim

Dissassembly

Looks like you have already done the hard part.  Simply pop the bottom cover off the truck and pull your wheelsets out. 

P.S.  The bottom cover usually holds the sideframes in place with a small tab.  If you forced the sideframes off before removing the bottom cover, then you may have well broken those retaining tabs.  Good luck and let us know how you made out.