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Natural Patina-color for A286 CRES?

Natural Patina-color for A286 CRES?

Natural Patina-color for A286 CRES?

(OP)
Background... I was handed [3] JO-Bolts, and was told they were A286 CRES. I was asked about their coatings.

Two-of-the-3 obviously had solid film lubricant finishes on the sleeve... but each had different head markings. The SFL finish on one was smooth/fine... the second was rough and 'thick'.

The 3rd one had a 'ruddy yellow-brown metallic patina' that was definitely NOT chromated-cadmium plating. Soooo I ass-u-me-d it was bare A286. However, It started bugging me, because the natural patina for A286 that I was familiar with was more 'light-golden-yellow-tinged-dull-silver'. The more I looked at the JO-Bolt, the less I was convinced it is A286.

Is there a realistic probability that this bolt is A286 but with heat-treatment darkening or staining of some-kind??

NOTE.
I just-happen-to-have an [unserviceable] Inconel [Nickel Alloy] 625 hot-air-duct assembly on a cabinet top near-by... and it struck me that the JO-Bolt's and the Duct's patinas were strikingly similar... ruddy yellow-brown . All-of a sudden it hit me: could this JO-Bolt may be an Inconel 718 JO-Bolt.

See attachment for fairly decent color photos of the JO-Bolt... assuming Your monitor's colors present like my monitor... http://files.engineering.com/getfile.aspx?folder=a...

Your comments? Speculation? appreciated.

NOTE.
This JO-Bolt has head markings that are fairly inscrutable, so I'm gonna-hafta figure-out the coding... and probably get a spectrographic analysis of the cleaned part sleeve.

What a pain... these 3-parts were all mixed together in the same stock-bin for general structural use.

Regardless The SFL coated bolts are 'OK' in aluminum... but the bare JO-Bolt is guaranteed to be highly dissimilar to aluminum.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: Natural Patina-color for A286 CRES?

Looks like standard heat tint from aging to me.
The color (oxide thickness) is a function of temp, humidity, and surface finish.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Natural Patina-color for A286 CRES?

(OP)
Ed... do You think most of the A286 fasteners [bare passivated] I'm used-to seeing get this surface color stripped-off during final-grind/passivation processing?

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: Natural Patina-color for A286 CRES?

A good surface and careful processing usually results in a lot less color.
Often these end up bead blasted, machined, or pickled and then passivated, these would be bright.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Natural Patina-color for A286 CRES?

(OP)
ES... Hmmmm... potential quality issues also... lovely.

Also..NOTE.
Head markings are a LOT more obscure than I anticipated... can't make sense of the info.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: Natural Patina-color for A286 CRES?

(OP)
Kwan thumbsup2

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: Natural Patina-color for A286 CRES?

A286 is so easy to get heat tint. it discolored even after bright anneal, say <-40F H2 anneal. For annealed products, acid clean or polish grinding is often added to clean heat tint.

RE: Natural Patina-color for A286 CRES?

(OP)
Kwan, MagBen, All... Thanks for shedding light on this!

I removed the drive-nut and used an old-fashioned abrasive-rubber '#2 pencil eraser' to clean-up the head, so markings stood-out. Yep A286!

MagBen... all-other bare [aerospace] A286 fasteners I've seen have a 'dull-silver-metal with a slight yellowish-sheen' appearance... because they have been appropriately acid-passivated [typ AMS2700] which removed the discoloration.

I shudda-known... over almost 40-years doing this I have discovered several fastener OEM awsh*ts as a result of miss-processing parts one-way-or-the-other.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: Natural Patina-color for A286 CRES?

Passivation will not remove the heat tint, pickling will.
And in aged A286 a pickle should be followed by a bake out cycle.
We get A286 out of Bright Anneal with no discoloration, but it is much more difficult to prevent it in aging (requires lower O2 and DP at the lower temps).

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

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