Stainless steel question

I've obtained a dip tube that is stainless steel, but the nut portion of the compression fitting has a nasty black coating. It is labeled Parker 316 TW. I tried scrubbing off a bit of the black stuff and saw some shinier metal underneath, but I'm not sure I could clean the whole thing since it's seemingly permanently attached to the dip tube.

The black stuff rubs off on my fingers and is difficult to remove, so I'm concerned about putting it in contact with my beer.

Anybody know what the black crud is and/or how to remove it?

 

Got a pic?

Parker 316 TW

 

You can see the partially cleaned area on the left.

 

I would just sand it down and scrub the heck out if it with BK Friend. One thing to possibly do is put it in an acid solution and see if anything comes off the nut. You are in SA so go to HEB and get their high strength vinegar ~9% and soak it in that for a while and that might help a bit.

-G

 

I keep a gallon of that handy for making a cleaning solution for my showers, so I'll give it a whirl. Thanks.

 

Looks like anodizing.

http://en.wikipedia.org/wiki/Anodizing

I've heard that lye or oven cleaner might remove the anodizing.

 

If the nut is stainless steel it is not anodizing but more likely Black Oxide coating or simply a paint of some sort. If the nut is aluminum it could very well be anodizing but that does not typically rub off on the fingers.

I would try the solutions mentioned above first but if that does not work find someone to bead blast it for you.

 

I actually have 2 nuts (!!!), so I just put one in a 9% vinegar solution and the other in a strong PBW solution. I'll let them soak all day and see if either dissolves the mystery gunk.

 

It's a molybdenum coating. I called Parker about this last year as a few of us on the forum got some coated ones like that. It won't come off. I tried sanding before calling them. It's bonded on there with something. The guy I talked to said not to use it in an immersed situation. I replaced it with nuts from the A lok series.

 

You're right, I just looked it up and found the information below. They certainly do feel a bit greasy.

I'd like to replace them, but the straight end of the tubes seems to be enlarged slightly and I can't seem to get the nut to slide over the bend in the middle.

 

I have those kind of nuts on my thermowell adapters on the outside of the pot, they should be OK there shouldn't they?

 

I would think so. I don't think the liquid would come in contact with the nut itself.

ETA: ....but I'm not totally sure.