Tig welded keg with some rust?

[pointhunter75]

Well I finally completed my electric keg setup and boiled some water, drained water and a few days later I shine a light in the keg and there's a little rust around the bottom drain and side element hole where they're burned through a little from the tig. Is that ok and common? I didn't think this stainless would rust. Used stainless bungs on the outside. The rust is on the little burned through nipple spots where the tig got a little hotter than other spots.

[corene1]

That doesn't look right at all. Do you know what filler rod they used? Looks like some puddle contamination while welding. Can you reach in and grind the surface clean? Then wash thoroughly with some lemon juice or citric acid to re pacify the area. I would also take a good magnet and set it on the weld bead to make sure they used stainless filler rod. I have seen people use ferrous steel rod to do the welds before and it looks similar to your picture. If they did use a ferrous steel filler rod the weld bead will be a blend of the 2 and be slightly magnetic. It will also rust constantly.

[pointhunter75]

It was welded with 316 rod he thinks. Gotta wait to see his son that tigged it and ask him. We tried a magnet on the rod he used and it won't stick at all...haven't tried the keg yet. What do I do? Grind the bungs off and take it to a welding shop?

[frunobulax]

It doesn't look like he made a sanitary weld by using a shielding gas (argon) on both sides of the weld.

[RedwoodHillBilly]

It doesn't look like he made a sanitary weld by using a shielding gas (argon) on both sides of the weld.

My thoughts also. How much room do you have for access to the weld? A thought that I had was to do an electro-polish on the inside. It isn't that hard, all you need is some phosphoric acid, an electrode and a power supply. This will passivate the weld.

I've done it with a small SS rod wrapped with exhaust wrap from the auto parts store. For a power supply, you could use a manual battery charger, 'tho I used a bench power supply that I could control current.

BTW, phosphoric acid is nice to have in your tool box for controlling ph.

[pointhunter75]

This is a follow up....I got another keg and had another friend tig it and I've still got a little rust on the inside of one of the welds. He purged with argon. There bottom drain weld looks fine but the side weld for the heater element has a little rust. I'm gonna try some lemon juice on it. I'll update. Tungsten electrode and stainless304 tig stick was used. I'm so frustrated.