Disimilar metals
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Posted by: Bobby J. ®

04/25/2006, 20:56:22

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Can anyone tell me what I may expect to happen if I thread a brass, 1/8" male pipe thread fitting into a aluminum, 1/8" female pipe thread fitting. This is in the coolant system of my automobile and is therefore exposed to temperatures of 180 degrees F.
Thanks.







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Re: Dissimilar metals
Re: Disimilar metals -- Bobby J. Post Reply Top of thread Forum
Posted by: rconner ®

04/26/2006, 17:06:32

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While I'm not an expert in brass or aluminum fittings, if this were my old beat up car I'm not sure I'd worry much about this couple (I suspect any galvanic corrosion that might occur would probably be spread on the aluminum/anodic? side of the couple, and if there is a relatively large area of aluminum in the area I'm not sure there would be any significant attack for a good while.) I guess if this were in an easily visible area in your engine compartment and no electrical etc. stuff immediately below it the risk would be less, as you could sneak a peak at it in the future when you do routine maintenance? -- probably also wouldn't hurt to put a good wrap of some teflon tape on the male brass threads when making the connection.







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Re: Re: Dissimilar metals
Re: Re: Dissimilar metals -- rconner Post Reply Top of thread Forum
Posted by: Bobby J. ®

04/30/2006, 15:49:25

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Thanks to everyone for your response. I've gone ahead and installed the fitting.
Again Thanks,
Bobby







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Re: Disimilar metals
Re: Disimilar metals -- Bobby J. Post Reply Top of thread Forum
Posted by: Kelly_Bramble ®

04/26/2006, 08:22:16

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See the following webpages:

About Galvanic Corrosion
/corrosion/galvanic_corrosion.htm

and

Galvanic and Corrosion Material Capatability
/corrosion/galvanic_corrosion.htm








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Re: Disimilar metals
Re: Disimilar metals -- Bobby J. Post Reply Top of thread Forum
Posted by: Marky ®

04/26/2006, 08:09:14

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I'd be concerned with corrosion inside the brass fitting.







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Re: Re: Disimilar metals
Re: Re: Disimilar metals -- Marky Post Reply Top of thread Forum
Posted by: randykimball ®
Barney
04/27/2006, 15:46:02

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FYI... some recent (to remain un-mamed) auto makers... have not been so wise in this department. Several models have a pot metal heator hose outlet on the intake manifolds that turns to mush in a few years....




The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

Modified by randykimball at Thu, Apr 27, 2006, 15:47:17


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Re: Re: Re: Disimilar metals
Re: Re: Re: Disimilar metals -- randykimball Post Reply Top of thread Forum
Posted by: Kelly_Bramble ®

04/27/2006, 16:30:30

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It never ceases to amaze me when automakers miss obvious corrosion risk. When I think back at the old top post battery design, I just cringe. Copper - Lead - Lead + oxygen + battery acid. No wonder battery terminals where always causing problems and required constant maintenance. The newer side-post battery design is almost too obvious a design fix.

The Brass - Aluminum interface has a anodic difference .95 - .40 = .55, which is not good, except in a controlled environment. The following is my best application suggestion:

Use a thread sealing compound of some sort (RTV is a possible option). Just keep out the oxygen!
Always use anti-freeze in the cooling system.

Chances are the brass against aluminum will last for awhile without any of these precautions.

Your can't find an aluminum fitting?








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