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Old 10-02-2013, 02:23   #1
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Mounting stainless steel on aluminum

Lately, I have been supplying quite a few compressors and scuba tank fill panels to owners that are either building new or are retrofitting the all aluminum boats. However, I recently had two orders canceled because we use stainless instead of aluminum for the panel.

Since I have only done one installation and shipped off the rest to builders/refitters, I am not quite sure what is being used normally for insulation between the stainless and aluminum to minimize galvanic corrosion.

We used simple nylon insulating washers. Is there something different that the boating community uses that we can suggest instead?
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Old 10-02-2013, 04:08   #2
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We have recently replaced some outlet plates with stainless steel equivalents on our aluminium mast and used Duralac Barium Chromate paste to isolate the two dissimilar metals, this is widely used in the marine industry to prevent corrosion. I hope this helps. Regards Magnum
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Old 11-02-2013, 18:47   #3
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Re: Mounting stainless steel on aluminum

Tef Gell Comes in little tubes that you could send with the parts.
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Old 11-02-2013, 19:25   #4
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Re: Mounting stainless steel on aluminum

I found both items and they both sound great if we were screwing stainless into aluminum. However, it really sounds like they are both primarily anti seize. I will keep them in mind for some of our other projects.

However, what the owners are concerned about is where the flange of the filler panel comes in contact with the bulkhead ... not the holes.

From the picture, you can see the 1" flange where we drill holes so that it can be bolted to the bulkhead. On the one installation I did, I used nylon insulating washers for the four holes and it made the panel stand out a tiny bit from the bulkhead. The owner didn't notice it until I said something and he told me I was being too picky. But, that's just me!

Will the grease/gel work here? I guess my question should be what should I put between the flat to flat parts?
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Old 11-02-2013, 19:29   #5
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Re: Mounting stainless steel on aluminum

Tef gel is not just an anti-sieze it has body and does not flow. It would work fine as a barrier between 2 flat surfaces, In my experience.
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Old 11-02-2013, 19:31   #6
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Re: Mounting stainless steel on aluminum

I believe that butyl tape is a simple solution for this application.
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Old 11-02-2013, 19:32   #7
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Re: Mounting stainless steel on aluminum

Quote:
Originally Posted by rcontrera View Post
I found both items and they both sound great if we were screwing stainless into aluminum. However, it really sounds like they are both primarily anti seize. I will keep them in mind for some of our other projects.

However, what the owners are concerned about is where the flange of the filler panel comes in contact with the bulkhead ... not the holes.

From the picture, you can see the 1" flange where we drill holes so that it can be bolted to the bulkhead. On the one installation I did, I used nylon insulating washers for the four holes and it made the panel stand out a tiny bit from the bulkhead. The owner didn't notice it until I said something and he told me I was being too picky. But, that's just me!

Will the grease/gel work here? I guess my question should be what should I put between the flat to flat parts?
You could mount the panel to a plastic or wooden plate and send with. And then they can mount the plastic/wood to their boat.
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Old 11-02-2013, 19:41   #8
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Re: Mounting stainless steel on aluminum

In this case the mounting bolts need tuff gel, and between the flange and the hull there needs to be an isolater. I would think a full leingth strip of 1/16 starboard (or gasket material) would be ideal.
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Old 11-02-2013, 19:48   #9
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Re: Mounting stainless steel on aluminum

Whatever you bolt-up to untreated metal of any type (almost) where there's a flange/thread involved it will possibly allow a cell to become active where moisture and dust can microscopically accumulate.

The Duralac that Magnum refers is very good and is my choice, the thin nylon/teflon washers you used are a great idea, but just seal with Duralac by brushing on, in the mated area and it will not let you down.

It must be re-coated if unbolted in the future. I've retired from metal boatbuilding but continue to use Duralac on our current boats ally and SS.

Cheers there may be similar products.
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Old 11-02-2013, 19:49   #10
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Re: Mounting stainless steel on aluminum

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You could mount the panel to a plastic or wooden plate and send with. And then they can mount the plastic/wood to their boat.
Woods not good Delmarrey it will hold moisture like a sponge and will no doubt have acidic Tannins etc in it.

Wood straight on any metal is corrosion city.

Cheers.
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Old 11-02-2013, 19:50   #11
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Re: Mounting stainless steel on aluminum

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Originally Posted by svtrio View Post
I believe that butyl tape is a simple solution for this application.
Carbons in Butyl tape will or may attack the ally.

Cheers.
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Old 11-02-2013, 19:58   #12
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Re: Mounting stainless steel on aluminum

I 2nd the use of butyl tape.

Need Butyl Tape ?? Photo Gallery by Compass Marine at pbase.com

Tuff Gel just on the screws and thread
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Old 11-02-2013, 20:01   #13
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Re: Mounting stainless steel on aluminum

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Originally Posted by Lagoon4us View Post
Woods not good Delmarrey it will hold moisture like a sponge and will no doubt have acidic Tannins etc in it.

Wood straight on any metal is corrosion city.

Cheers.
Yeah! I agree!
In my mind I was thinking wood coated in epoxy, I just didn't state that.
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Old 11-02-2013, 20:07   #14
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Re: Mounting stainless steel on aluminum

The epoxy is good but you'll still need to protect the ally where the natural oxides fail. Duralac can be relied on it is simply good stuff, like Vegemite essential!

Cheers
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Old 12-02-2013, 23:49   #15
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Re: Mounting stainless steel on aluminum

Thanks all for the feedback. I really can't bolt on a plastic or wood back as that would make annual maintenance (checking all fittings and connections) more difficult.

I will pass on the information.
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