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Old 03-22-2013, 04:02 AM   #1
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Default 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?

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Old 03-22-2013, 04:06 AM   #2
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Got a pic?

Parker 316 TW

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Old 03-22-2013, 04:12 AM   #3
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You can see the partially cleaned area on the left.

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Old 03-22-2013, 05:36 AM   #4
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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.

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Old 03-22-2013, 05:44 AM   #5
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Quote:
Originally Posted by HDIr0n View Post
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.
I keep a gallon of that handy for making a cleaning solution for my showers, so I'll give it a whirl. Thanks.
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Old 03-22-2013, 11:15 AM   #6
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Looks like anodizing.

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

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

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Old 03-22-2013, 02:56 PM   #7
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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.

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Old 03-22-2013, 03:25 PM   #8
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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.

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Old 03-22-2013, 03:33 PM   #9
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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.

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Old 03-22-2013, 03:46 PM   #10
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It's a molybdenum coating.
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.

Quote:
Molybdenum disulfide coated bolts are commonly used to improve the performance in extremes of load carrying capacity, operating temperature and coefficient of friction. This coating provides effective lubrication in a wide range of loads, in many cases exceeding 250,000 psi. Moly coatings lubricate sacrificially by transferring lubricant between the two mating surfaces, which helps to reduce both wear and the coefficient of friction. Moly coatings are a combination of molybdenum disulfide lubricant and high performance resins. The coating is thermally cured to bond thoroughly with the base metal of the coated part. Moly coated bolts can solve problems associated with corrosion, chemical exposure, and abrasion. offer excellent corrosion and chemical resistance and a barrier protection better than phosphate. With Moly’s exceptional barrier protection, it is appropriate for more severe environments and is often used in chemical processing and oil field equipment.
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