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Author Topic: Rust on Bohm heater cap  (Read 2212 times)

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Rust on Bohm heater cap
« on: July 30, 2025, 10:09:59 pm »
Anyone else every noticed rust on the heater cap of their Bohm engines?

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Re: Rust on Bohm heater cap
« Reply #1 on: July 30, 2025, 11:54:08 pm »
Scorched steel makes it easier to oxidize ..... and you live right near the ocean in a salt air environment.

Even here in the high and dry of the intermountain desert I find a thin layer of fine rust on the heat caps of some of my Solar Engines and PM Research Stirling Cycle Engines!
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Re: Rust on Bohm heater cap
« Reply #2 on: July 31, 2025, 12:02:36 am »
Quote from: Stoker on July 30, 2025, 11:54:08 pm
Scorched steel makes it easier to oxidize ..... and you live right near the ocean in a salt air environment.

Even here in the high and dry of the intermountain desert I find a thin layer of fine rust on the heat caps of some of my Solar Engines and PM Research Stirling Cycle Engines!

My PMR's all will get some surface rust if I don't oil the end caps after running them, but they are carbon steel.
The Bohm end cap is stainless, I've seen a slight rust stain even on 316 stainless in marine settings, but that's a fair bit of rust on that end cap.
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Re: Rust on Bohm heater cap
« Reply #3 on: July 31, 2025, 12:09:06 am »
I just sent an email to Bohm with the photos, be interested (if they ever answer me) to see what they say.
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Re: Rust on Bohm heater cap
« Reply #4 on: July 31, 2025, 12:31:03 am »
Didn't know that Bohm's heat caps were Stainless. But there is Stainless and there is Stain Less, depending on the alloy used. Check it with a magnet, as I know for marine rigging, Stainless wire-rope that will attract a magnet is considered to be very inferior at corrosion resistance!
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Re: Rust on Bohm heater cap
« Reply #5 on: July 31, 2025, 01:10:51 am »
Quote from: Stoker on July 31, 2025, 12:31:03 am
Didn't know that Bohm's heat caps were Stainless. But there is Stainless and there is Stain Less, depending on the alloy used. Check it with a magnet, as I know for marine rigging, Stainless wire-rope that will attract a magnet is considered to be very inferior at corrosion resistance!

A magnet is not interested in it.
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Re: Rust on Bohm heater cap
« Reply #6 on: July 31, 2025, 09:16:52 am »
The oldest Bohm I have is about 28 yo, no rust. I use 95% alcohol in the burner. Possible cause might be if a higher water content in the fuel combined with the heat would aid in forming rust.
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Re: Rust on Bohm heater cap
« Reply #7 on: August 01, 2025, 06:48:26 pm »
Bohm got back to me -


Hello,
we use 1.4305 Stainlesssteel,
Chemical X10CrNiS18-9,
Corrosion resistance Medium
Not resistant to intergranular corrosion
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