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Old 09-10-2009, 07:51   #1
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Monel vs Stainless

How can you tell the difference between monel and stainless, for example, when a seller tells you that the fuel tank is monel? What are the best materials for water and deisel tanks?
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Old 09-10-2009, 08:11   #2
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Good question on how to tell the difference. Not sure there...but I do know monel is supposed to be a superior alloy to stainless steel in terms of corrosion resistance etc. Very expensive stuff. Probably not something you're going to go buy these days for a fuel tank or whatever, but if it's there, and in decent shape, I'd leave it right where it is.

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Old 09-10-2009, 08:58   #3
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Monel has a somewhat duller appearance as it has no chromium. It's a nickel-copper alloy. The K-500 version includes some titanium for strength. I had some valve stems made of K-500 monel for acidic salt water service (oilfield, produced water in a CO2 flood) where 316 SS was dying in 3-4 months. Last I knew, those valve stems had lasted 6 years.

If you attempt to polish a small section, it will be pretty obvious that it's not SS due to the dull appearance. It will look much more like nickel than like chrome. Monel is very, very corrosion resistant, but is typically much more expensive than even 316L stainless.

Monel is a superior fuel tank material, hard to imagine anything better. If you could afford it, it would probably be great for water tanks, too, but at the high end these are usually 316L stainless.

I am aware of only one US production boat manufacturer who has used it for fuel tanks - Hinckley - but there may be others.
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Old 09-10-2009, 09:11   #4
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We have monel tanks. it's a dull grey and the fittings are (supposed to be) bronze rather than stainless or plastic. If exposed to spray, it may have some greenish flecks.
I can maybe take a pic this weekend.
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Old 09-10-2009, 09:19   #5
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Thanks, that is what I needed. Asking because I might go look at a boat adv. in YW and didn't want to go in blind. After monel and 316 what is next best?
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Old 09-10-2009, 09:39   #6
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Polypropylene or aluminum I'd guess for water. I don't like the idea of fibreglass tanks.
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Old 09-10-2009, 09:51   #7
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I havent looked but I dont believe monel will normally be magnetic....? Stainless will often be magnetic... at least slightly... Monel is extremely good stuff but you dont see it much anymore, although I think it's still available readily for prop shafts.... you wont see any rust on monel.
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Old 09-10-2009, 09:54   #8
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Thanks, that is what I needed. Asking because I might go look at a boat adv. in YW and didn't want to go in blind. After monel and 316 what is next best?
Ultra High Molecular Weight Poly Ethelene (UHMW, UHMWPE; UHMW-PE) comes to mind.

It's rated as food grade and is very chemically resistant
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Old 09-10-2009, 09:58   #9
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I havent looked but I dont believe monel will normally be magnetic....? Stainless will often be magnetic... at least slightly... Monel is extremely good stuff but you dont see it much anymore, although I think it's still available readily for prop shafts.... you wont see any rust on monel.
Monel is non-magnetic. It can get a kind of dark green corrosion on it, but not significant (even after 45 years).
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Old 09-10-2009, 10:09   #10
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Ultra High Molecular Weight Poly Ethelene (UHMW, UHMWPE; UHMW-PE) comes to mind.

It's rated as food grade and is very chemically resistant
If I have to fabricate a tank will this stuff work? I mean that most tanks are shaped irregular so does this stuff come in sheets, rolls, etc.?
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Old 09-10-2009, 12:04   #11
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If you can sketch it, try Tank Depot...
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Old 09-10-2009, 12:36   #12
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Thanks. I'll file this site.
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Old 09-10-2009, 15:12   #13
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If I have to fabricate a tank will this stuff work? I mean that most tanks are shaped irregular so does this stuff come in sheets, rolls, etc.?
It does come in sheets. Try garland manufacturing or any of number of others

Another alternative that comes to mind (for water and wastewater) since you mention the irregualar shape is a flexiable tank that hardens.

You put the flexible out tank in the space, inflate it and insert a UV bulb which hardens the tank. Then you put in the liner tank which is made up of food grade polythene.

Cheechako: I checked your link for any reference to UHMW with no results, were you speaking of something like plastic or ... something else?
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Old 09-10-2009, 17:09   #14
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They made a great custom Plastic Blackwater tank for me. reasonable prices. Nice thick stuff like 3/8. Have to ask if they do diesel tanks though...
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Old 09-10-2009, 17:15   #15
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Polypropylene or aluminum I'd guess for water. I don't like the idea of fibreglass tanks.
Fiberglass tanks for water are great way to go - jellycoat inside. Gellycoat is inert to water and does not rust. But a GRP tank probably just possible in a new build.

The MONEL things we have here are - more goldish in colour than SS and (...) more expensive - how much would a tank be??? (A monel rivet is 200% the price of SS I guess (?)).

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