What is your prefered method to cleaining metal before tig welding

I was attempting to weld some 16g tube today and I always hit it with a flap disk and wipe clean with acetone on the outside, but I noticed that I was having one hell of a time because of the contaminants on the inside of the tube where getting pulled up to the surface. :mad:

I didn't really have much probs with not cleaning the inside of the tube when welding
.120 tube, but the thinner stuff was popping and spewing.

What is your prefered method to cleaning the inside of a tube before welding? or do you even bother?

I've never done this kind of welding.
What I typically hear people doing when tube welding is to back-purge it with argon.

Go about 3/5 of the way down on this page and you will see a simple Y adapter for back purge and how he set it up with the tube. You will want to seal the argon inlet reasonably well, but leave a little hole in the other end/ends so that the argon can push the air out.
http://ls1tech.com/forums/cadillac-c...ictures-3.html
http://img403.imageshack.us/img403/3...purgevalve.jpg
http://img403.imageshack.us/img403/1007/backpurge.jpg

I'm aware of back purging when welding SS, but i'm only welding mild steel.

The reason I ask is I have seen people tig weld exhaust tube with nothing more than using a wire wheel on the outside and I've also seen people clean it good enough to eat off of... both with seemingly equal results. I, on the other hand not so good of results.

Cleaning the inside of the tubing (or back side of the weld joint) is important if you will be fully penetrating. That is usually the case with a butt welded joint on .065" thick tubing.

The main thing is to get any hydrocarbons off of there. Some solvent soaked into a paper towel can work, if the edge of the tubing isn't so ragged that it will cut the towel into bits. If it does have burrs, some deburring can be useful. There are little tools that can make quick work of deburring. I have a tungsten carbide scraper blade I just grab and use in my hands. It never needs sharpening. If you have new tubing, (especially mandrel bent pieces) it may have some oil from being manufactured. Possibly even a thick, wax type coating, which some heat and/or solvents can remove. To clean deep into a tube section, I like to wad a cloth rag into a ball, grab it with one of those flexible long reach type tools, solvent soak it, and run it in and out of the tubing.

Used exhaust tubing may have corrosion, soot, etc. To remove heavy scale you can use something like a Die grinder with a cartridge roll, cross buff, or flapper stick, followed by a solvent wash, if you want to get the inside really clean. If you don't have a die grinder, but have patience and some good ol' "elbow grease", a strip of emery cloth (sandpaper with cloth backing that comes in a roll...) over your finger can remove stuff. Follow up with a solvent wash. I find solvent in a spray can to be highly convenient sometimes. Can blow the solvent out with compressed air, or wipe it away with a paper towel or rag.

A cup or end brush that is sized to fit inside the tubing is yet another method.

If you weld on rusty steel, galvanized or other coated mild steel, don't breathe the fumes, and expect some live popping while welding. Take off any gas lens and use a regular collet body to save you gas lens screens.

Remember to never use chlorinated or fluorinated solvents like carb/brake cleaner or 1,1,1 tri...

Lots of good info, thanks!