Author Topic: Black Oxide Coating - Cylinder  (Read 1691 times)

Offline cwelkie

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Black Oxide Coating - Cylinder
« on: December 23, 2017, 10:34:13 PM »
I'm getting down to the "short strokes" on my Cirrus and have started putting black oxide on some of the parts for a bit of accent colour.  The Caswell coating kit is working well for me so far.

The main event is to be coating the cylinders.  It is simply for appearance; I think black cylinders will provide a nice contrast between the aluminium castings and the bar stock head.  I've taken a pause to sort through the consequences, if any, of getting black oxide on the inside (and already lapped) surface.  Have any of you experience or pointers to share in this regard?  My first thought is that it shouldn't be an issue; the coating will likely wear off quite quickly upon start-up.

Thanks
Charlie

Offline Vixen

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Re: Black Oxide Coating - Cylinder
« Reply #1 on: December 23, 2017, 11:16:47 PM »
Hello Charlie,

The black coating is not an iron oxide but is selenium (tin) based. The coating thickness is cosmetic and only molecules thick, it's not very hard.

I doubt it will make any difference if you get some of the black inside the cylinders, it will quickly wear off when the engine runs.

To be on the safe side, I pressed two rubber corks into either end of each cylinder, when I black coated the cylinders for by Bristol Mercury radial engine. It worked perfectly and completely masked the cylinder bore.

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Brian Rupnow

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Re: Black Oxide Coating - Cylinder
« Reply #2 on: December 24, 2017, 01:17:49 AM »
I used to work in a shop where a lot of our "stuff" was sent out for black oxide coating. It makes for a beautiful cosmetic appearance, but even though it was always said to add no measurable dimension to the coated parts, it would "gum up" mating parts and have to be removed. It made our machinists crazy. Perhaps it didn't actually add anything measurable, but it certainly screwed up surfaces that had to slide against each other.----brian

Offline cwelkie

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Re: Black Oxide Coating - Cylinder
« Reply #3 on: December 25, 2017, 03:10:55 PM »
Thanks Brian and Mike
I've decided, in the interests of science curiosity to plug the ends of two cylinders and leave the other two open.  Still don't think the colour/coating is so durable or thick as to cause a problem.  If it is, I can always re-lap those two cylinders a tiny bit.

BTW - small (1 1/8") replacement sink stoppers worked well to plug the cylinder ends.

Merry Christmas everyone.
Charlie

 

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