Welding Tips and Tricks

No, really, actual soldering, not a derogatory term for poor welding skills.

I need to know what supplies I need to solder a steel sump onto the bottom of a (new, unused) fuel tank. I've done enough reading to know that no two people recommend the same stuff for the same soldering job, everybody has their personal favorite combo, and for this one little thing I only need something that will work well. Just too many choices - copper irons vs. torch(es of all various kinds), about a thousand different flavors of solder, and at least twice that many of flux. It's all plain mild steel, so nothing exotic like aluminum or stainless.

I'm being paranoid about rust down the road, so I know I want the whole thing tinned inside and out, and soldered on so I don't have to grind off the tank's nice new coating and make a huge mess. Anybody want to offer up a list of stuff that'll all work well together and get the job done?

Yes, you're being paranoid.

Tinning everything is overkill. Primer and paint will accomlish the same end.

If you know how to solder, plain 'ol plumbing solder and flux from the Home Depot will do.

This is the lowest temperature option, and won't damage much paint.

Steve S

I don't think paint will survive on the inside of the little sump box exposed to the fuel, will it? I'm much less worried about rust on the outside, but once I've tinned the inside of the sump, doing the outside too isn't much more work. The new tank is coated inside and out with whatever new steel tanks are coated with - it's soft and scrapes off like solder, so it's tin and... who knows, probably not lead, not these days - and I lost the last tank to rust issues (but it was the 30 year old original), I'd hate to have that in the back of my mind that the part I added was just plain bare steel, and also at the lowest point where any water would naturally collect.

Instructions that come with the store-bought sump kits recommend using a tank sealer kit (like Eastwood, or whatever), but that's aimed most users who will be installing it on a previously used tank, where that might be the better option especially if a used tank has any minor rust issues starting. Just seems silly using a sealer kit on a new tank that has a good tin coating on it already. If the tank wasn't brand-spankin' new I'd just tig weld it and pour in some sealer.

I know soldering but only from small electronics, never anything structural or even plumbing-related.

You don't need to do anything to the inside. Gasoline might as well be very thin oil. The sump will never see oxygen unless you run it dry, so will not rust.


If you've never done any serious soldering (electronics doesn't count--- different animal), you might ask among your friends.

I can tell you how, in great detail, but there's no replacement for experience where fuel is involved.

Steve S

This is starting to sound, unfortunately, like the 'if you have to ask, you shouldn't try it' type of advice. But being hardheaded I just tried anyway on a test spot on the new tank. The coating isn't traditional zinc galvanized, it's something else, and melts very easy even with only a little pocket butane torch. Roll of acid core solder I had on hand flows and sticks nicely on it, as well.

I was under the impression that the risk of explosion for a tank that has never had a drop of fuel in it was about as close to zero as its possible to get. If that's incorrect, I have a whole bunch of other basic assumptions about the world around me I will have to reevaluate - things like 'I better not walk on this solid floor, I might fall through and die' or 'going outside is dangerous, gravity might fail to keep me from floating away into space.'

Correct.

No explosion danger on a virgin tank.

What I meant by "...where fuel is involved," was, be sure you're confident in your ability to produce a strong, reliable joint so there are no worries about leaking or breakage somewhere down the road (pun intended).

If your test area tinned out so nicely, I'd go for it.

Good luck,

Steve S