Rust inside TC racking arm tube

wootz001

Not sure that rust is the right word, but I have 2 brand new stainless racking arms with the same issue. There is a white powder and straw/brown discoloration inside both tubes right where the "indicator" rod was tacked onto the outside of the tube. I've scrubbed down to bare metal with barkeeper's friend, and run through a citric acid passivation step (4% ~1hr at 140F), but it keeps coming back. Sorry, really hard to get a good picture. Any ideas what it could be, and what to do about it?

wootz001

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hotbeer

Stainless steel will rust in the right conditions. But what you are describing sounds more like some deposits of some kind from the things you had in it. Or just stuff from manufacturing such as welding that didn't get cleaned off properly and maybe you missed seeing it before first use.
I am sort of taken aback by the machining marks still left inside the fitting in your last picture as well as some of the stuff I think I'm seeing on the flange in the blurry part of the pic.
Even the very inexpensive SS sanitary fittings I've been getting from sellers on AliExpress are more well finished with few machining marks inside them or on them.

wootz001

Both are brand new, never used other than cleaned and put through the Passivation step I described. The top is a Spike brewing, bottom came with a conical from Stout Tanks.

hotbeer

I'd ask them if that the quality finishing they really want to be known for. Even the second pic showing where the smaller tube is entering the bigger tube looks pretty lousy welding and/or finishing.
But admittedly the pics themselves are blurry and it might be better than what I'm able to see.

wootz001

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hotbeer

Outside looks better in that pic than I was thinking. Still a lot of dings and minor scratches than I prefer to see. Did they have plastic covers on the flanges when they were new?
My biggest concern though was the markings down inside the hole going well down the inside.
You probably need to get some opinions from others. I've only got the stuff I ordered and received as a frame of reference for how well the finish should be. And I'm highly impressed with the finish externally and internally on the fittings I received.
If you don't keep those fittings installed and wet with beer but for the time you are actually transferring beer, I'd probably have no issue with them. Other than I might up my sanitizing with something stronger and broader.
edit...
And now going back and inspecting the more recent order of sanitary fittings I just got a few days ago, the one with the smallest hose barb, 3/8th inch external, has some brown stuff just below the hole. Looks much like it may be some flux or something they applied before welding together.
Very smooth and evenly brown the entire inner radius. Tried to get a pic, but I couldn't get a good angle on it with the camera. But I did note that the camera does seem to exaggerate the scratch marks some over what they look like with a bare eye or magnifying glass.
Still not too concerned about that as the hose barb will only be used briefly. Though I will try to get it off through various methods. The other fittings and larger hose barb looked good though.

McMullan

Cheap Chinese crap. Internal finish doesn't look polished and fit for sanitary purposes. I've had one or two TC fittings like this from AliExpress. They have reasonable quality TC ferrules, but pipes and barbs welded to them are absolute shite quality inside. Difficult to capture in a photo, but here's one:

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wootz001

I'll go ahead and inquire with the sellers and see what they have to say. Any thoughts on actually being able to fix and use these items in my fermenters? I get they may not be of spectacular quality, but they are what I have on-hand, and there is beer to brew.

McMullan

I'd sterilise them in a pressure cooker or oven before using them on the cold side.

wootz001

Thanks, I probably would not have come up with that on my own. Nice simple solution, at least for now.
I am guessing the machine marks and roughness of the tubing are a place to harbor nasties, just like scratches on plastic… the inside should be polished smooth right? I’ll say the marks show up worse in the pictures than in person. The inside of the tubing feels smooth, but definitely has a grain to it.
Any recommendations on where to get a master-crafted racking arm polished so finely it burns brighter than the sun?

Bobby_M

What you're seeing here

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and here

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Is less than ideal back gassing/argon shielding of the welds that happen mid-tube. The expected welding jig sends argon into the tube so that when the weld pool is molten, it can't come into contact with oxygen because it makes metal look like burnt sugar. I've done this before when I'm in the middle of welding and the phone rings so I turn the purge valve off. Then when I get back to it, I start the weld and realize I forgot to turn the gas back on. In these pictures, it just looked like the flow was a little sketchy because if it were off, it would look WAY worse. No solid answer as to why those circular gouges other than possibly insertion of a stiff rotary wire brush to try to clean up the weld sugar.

wootz001

Thanks, @Bobby_M for the explanation. Makes sense, and good to know its a manufacturing process related issue. Would you see any issues using these in a fermenter? And/or, is there anything I can do treat the sugaring and get them usable? I'd rather not junk them if I don't have to.

wootz001

FYI—Contacted Spike about their arm, customer service replied that it looks good to them and I should have no problems using it.