I have four tracks where I have soldered power wires to the underside of the rail. On every one, I notice that the rails get corroded right above the solder point. I clean them off and a day or two later, it's back. It gets bad enough that unless I clean it, that spot becomes a dead area even while the power tap still functions.

Anyone else encounter this?

Thanks...Joe

Joe,
Did you use acid flux, or acid-core solder, to make the connection?

It sounds like the acid might have leaked onto the upper rail surface. If so, it can be neutralized by a solution or paste of baking soda in water. Rinse with clean water afterward. But what's going on up top is also going on below, as the leftover acid eats the copper wire and the rail material inside the solder joint. Sooner or later, the result will be a joint that may look good on the outside, but has high resistance or doesn't conduct current at all, because the metals inside it have turned to non-conducting crud.

An acid-fluxed joint can last many years before it gives trouble, depending on the metals and the amount of acid in the joint. From your description, it sounds like there may be a lot in these joints.

Always use only Rosin Flux (check Radio Shack) and/or Rosin-core solder for electrical connections. And replace the acid-contaminated tip of the soldering iron with a new tip to be used only with Rosin. So the conventional wisdom goes, anyway.

If you used Rosin flux with a clean iron to make the connection, then it's something else :confused: -- sorry for the lecture.

-- D

Could you possibly have used acid core flux or solder instead of rosin core?
For my Tomy track I had 3 pcs. track made for dead section & 24 pcs. for power taps, all w/soldered wires.

I used light duty rosin core solder from Radio Shack. When I just pulled out the solder and flux, I noticed that the flux I used is for joining copper tubing. Is that a problem?

The track has been soldered for about 2 years and I've only really started to notice this a few months ago.

Thanks...Joe

Acid flux is for plumbing applications. That would seem to be the source of
the corrosion. :(

Acid flux is for plumbing applications. That would seem to be the source of the corrosion. :(

Ooops!

Thanks Dom

I'm curious about what you are using to clean the rails. I would use 91% isopropyl alcohol and a clean and trimmed solder brush to thoroughly clean the joint. Dry it with a clean cloth or compressed air. Use some LL track cleaner, electrical contact cleaner, or Rail Zip on the spot after everything is cleaned up.

I'm speculating that you are suffering from galvanic corrosion that is accentuated by the current flowing through the bimetallic solder/rail joint. The track being in a humid space or using water based cleaners would make it worse. The moister it is, the worse off you will be. This effect is a function of the solder material, so if you decide to resolder the joints, use a different solder formula than what you used the last time. I prefer to use an electronics grade rosin core silver solder (2% or higher silver content).

...I noticed that the flux I used is for joining copper tubing. Is that a problem?

The track has been soldered for about 2 years and I've only really started to notice this a few months ago.

I second Dyno Dom's opinion. Unless something basic has changed in the, oh, twenty or twenty-five years since I last paid attention to soldering technique (it could happen), plumbing applications use acid flux. Also:

Paste flux or "soldering paste" = acid.
Sal Ammoniac tinning blocks for cleaning iron tips -- not acid, but corrosive anyway, because of chloride salts. Don't put your "electrical" iron on one.

If it doesn't say "Rosin" or "Non-Corrosive," or at least something like "Safe for Electronics" on the flux package, it's almost certainly acid. Shun it. For soldering electrical circuits, that is.

-- D

I'm curious about what you are using to clean the rails.

When I clean the whole track, I first go around with a very very fine piece of sandpaper and follow up with Formula 409. However, the last time I cleaned the track, I had a lot of difficulty getting the track running as well as before the cleaning. That is probably the last time I use Formula 409. From now on, it's alcohol.

When I clean only the spot above the solder joint, it was a few swipes with the sandpaper and a wipe.

Some pieces of track seem to build up more junk on the rail than others. Must be different grades of metal that were used.

I'll be replacing the four "terminal" tracks with new pieces using the correct flux.

One thing I've always wondered - why would you ever need to replace the tip of a soldering iron? Doesn't seem to me it would ever wear out. I've never changed one and never saw the need.

Thanks...Joe

If the tip has been used with acid flux or acid core solder, it should be consider contaminated and not used for electrical work.

I've replaced 2 tips on my iron already, and another is due now. I've never used anything but rosin core solder and a bit of rosin flux only when needed. I don't know what kills the tips, but they do wear out. They get worn down at the tip to the point that they start hooking the wires your trying to attach..

Hmmm. I've never worn out a soldering iron tip either. I always "season" my tips by dipping the entire tip of the hot iron into a tub of rosin flux paste, then completely coating the tip with solder, then wiping all of the solder/flux off on a mildly damp sponge until the entire tip is shiny and coated with an ultrafine residue of solder. When the iron cools down completely (repeat - completely!) I clean off the tip with a lint free cloth or wipe that's been moistened with isopropyl alcohol.

If it sounds like I use a bit of isopropyl in working with slot cars, you're right. I learned how to solder in the military at a class taught by NASA. It was a 2 week long class. They were really big into keeping everything clean. I recommend getting yourself a snap cover "touch pump" alcohol dispenser bottle for your slot car garage. I prefer the wider glass ones with the metal lids. The plastic ones are fine too. Recycle your old t-shirts or dish towels by cutting them into little squares (whatever size you prefer, I like 3" x 3") squares and pack them into a plastic container with a lid. When you need to clean anything on your slot car, grab a square, tap it on the alcohol dispenser a couple of times, and you're good to go. For track cleaning I filled a spray bottle with isopropyl and spray a fine mist on a microfiber cloth for wiping down the track. Works very well.

Here are some samples of different alcohol dispensers:

Plastic:
http://www.fitzz.com/Liquid-Push-Down-Alcohol-Dispenser--Labeled_p_9058.html
http://www.tecratools.com/product464.html


Lab Quality with Metal Top: (the Caddy series)
http://www.purespadirect.com/MENDA-6-oz-Glass-Bottle-Clear-p/vu-201764.htm

This place has a wide assortment, but you can shop around for best price.
http://www.thefind.com/crafts/browse-menda-alcohol-bottle

These bottles are definitely the cat's meow for one hand dispensing of a quick shot of isopropyl. Some of them can handle other liquids, like thinner.