I've been repairing/cleaning/havin' fun for the last 5 years now but have yet to discover what I would call an excellent means of cleaning the chemically blackened die-cast side frames, especially those found on EMD trucks - they have so many cracks & crannies. The pictures below show untouched trucks as I got 'em, then one side cleaned with alcohol, then the other side cleaned with a heavy concentrate of Dawn dish liquid. The goal is to eliminate that nasty looking white stuff, which I assume is corrosion, not really dirt. On the backside of a side frame I chipped away some of the corrosion with a very small screwdriver flat blade and it does chip off, but it's waaaay too easy to scratch right through the chemically blackened layer.
I'm looking for something that will not scratch the blackened frames, so any kind of wire brush is definitely out, which kind of leaves just chemicals. I have in the past used WD-40 and/or lightweight oil, but those too seem to dry over time leaving a mostly unimproved surface.
Do you have a magic formula?
So the winner so far is Dawn - but I believe there must be something better. Let me know what has worked for you. I did do a number of searches on this forum, but didn't find anything despite knowing that I have read something in the past. Thanks!!!