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Old 12-07-2019, 11:28 AM
amaris amaris is offline
Join Date: Feb 2015
Location: Santa Ynez, CA
Posts: 269
Default Steel AN fittings on firewall?

I'm not sure where to post this, so I'll put it in my model type, but applies to all.

I'm concerned about using aluminum AN fittings (or any important aluminum components) in FF so people recommend steel. I've not seen stainless steel fittings, just steel. Is there not concern about galvanic corrosion between the stainless and the steel? Or does the benefit of steel on FF outweigh the risk of corrosion?

Allen Maris - 2020 Dues paid
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Old 12-07-2019, 12:12 PM
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rv8ch rv8ch is online now
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Default steel

I used all steel FWF and it is black with some kind of anti-corrosion coating. Seems to be the standard.
Mickey Coggins
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Old 12-07-2019, 01:01 PM
TS Flightlines TS Flightlines is offline
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Another never ending debate---Vans uses aluminum in some cases, and steel in others. We like stainless, but its a bunch costlier (?).
Personally I thinkn that if you had a fire hot enough to melt 2024T3 aluminum, then a lot of other things would go first.

Tom Swearengen, TS Flightlines LLC, AS Flightlines
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Old 12-07-2019, 01:13 PM
scsmith scsmith is offline
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The primary purpose for steel fittings FWF is for fatigue resistance in vibration environments. I use steel (or stainless) exclusively on the engine. On anything mounted firmly to the firewall, I will still use aluminum for large-size fittings.

Fire will likely burn through thin aluminum items (like a firewall-mounted cabin heat control valve) but in the time it would take to melt an AN fitting? A lot of other bad things will happen long before that happens.

One caution of using stainless fittings -- a stainless B-nut on a stainless flare fitting can seize and gall. Use a very light coating of nickel anti-seize.
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Old 12-07-2019, 02:43 PM
rapid_ascent rapid_ascent is offline
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Stainless fittings are available at among other places. They are more expensive, but I went ahead. I have my brake and fuel line bulkhead fittings in stainless. No aluminum passthrough of any type on my firewall.
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Old 12-07-2019, 09:34 PM
amaris amaris is offline
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Location: Santa Ynez, CA
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Thanks, everyone.

I think I'll go steel. It's a bit more but at least it's one less thing to be concerned with. Though as Tom points out, if it gets bad enough to worry about melting the fittings, I'm sure there will be many other issues to deal with too.
Allen Maris - 2020 Dues paid
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Old 12-08-2019, 05:47 AM
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DanH DanH is offline
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Use stainless rather than an oxide finish or plated steel. We want bulletproof fuel systems, so corrosion performance is notable. I've done one AOG call with rusty fittings. I don't know what got into the tanks, but a lot of steel parts looked like Brillo pads.
Dan Horton
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Old 12-08-2019, 07:43 AM
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acam37 acam37 is offline
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Steel and stainless steel JIC fittings can be purchased locally at just about any hydraulic shop. Most even carry braided SS teflon hose.
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Old 12-08-2019, 12:22 PM
amaris amaris is offline
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Location: Santa Ynez, CA
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I did look at the JIC but they were essentially the same price as the AN versions. All look to be about $35-45 regardless.
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Old 12-08-2019, 12:48 PM
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RV7A Flyer RV7A Flyer is offline
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Probably goes without saying, but just a reminder to make sure you get AN (or JIC) fittings, not SAE. That is to say, 37 degree flares, not 45.
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