bronze to stainless?

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bigdogeh
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bronze to stainless?

#1

Post by bigdogeh » Sun Nov 09, 2014 5:11 pm

Just had a question regarding the main water intake in my boat (intake for cooling water to heat exchanger). most as you know are made of bronze that i've seen. mine included. I wanted to plumb in a tee where there is an elbow and have one end plugged. the reason for this would be to make it easier to hook up my clear hose I use for winterizing. I would just remove the plug and thread in my clear hose ....at the moment I have to remove the heavy seawater hose (hydraulic) from the hose barbed elbow and it's always fight getting the hose end off. I usually end up stabbing myself once or twice on the reinforcing wire that protrudes from the end of the hose and i'm usually physically exhausted by the time i get it removed from the hose barbed ftg.... then hook up my clear plastic hose that i use to flush the system with rv antifreeze. my question is I have all the proper ftgs to replumb this (the complete seacock intake) in stainless. but just wondering if that would be a no-no and if i should just stick to the bronze?
thxs for any feedback, suggestions, etc... :thumbsup:
bigD

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Gypseas
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Re: bronze to stainless?

#2

Post by Gypseas » Sun Nov 09, 2014 7:14 pm

Instead of doing all that work would you be able to use one of these?

http://www.ebay.com/itm/Marpac-Marine-B ... 82&vxp=mtr

cheers

bigdogeh
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Re: bronze to stainless?

#3

Post by bigdogeh » Sun Nov 09, 2014 11:50 pm

thxs for the link gypseas.
Interesting idea. I actually tried shoving a hose that fit tight in the thruhull but unfortunately my trailer "hull support runner" covers about half the intake so it was impossible to get a good fit. if it wasn't in the way that would probably have worked though...

Chaps
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Re: bronze to stainless?

#4

Post by Chaps » Mon Nov 10, 2014 12:15 am

surprised to hear you've got a bronze thru hull on an aluminum boat. stainless would be way better as its fairly non-reactive (unlike bronze)
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bigdogeh
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Re: bronze to stainless?

#5

Post by bigdogeh » Mon Nov 10, 2014 4:22 pm

good to know Chaps,
Yes I have two bronze thruhulls/ seacocks... one for each engine. They have turned light blue with corrosion as most do. but that looks to be the only corrosion and doesn't seem at all serious. the aluminum itself doesn't seem to be reacting or corroding at all. that's why I was wondering if I should leave the system as is in bronze and just add a bronze tee with one end plugged. but seems a shame if i have all the stainless ftgs sitting here to completely do the project over. just want to do it the way that will be least reactive corrosion-wise I guess. the ftg itself that goes through the hull may be stainless, then from there converted over to bronze. I'll have to check next time i'm at the boat. it's either stainless or bronze, plated in some sort of chrome plate as it is a shiny silver colour with no hint of corrosion.
not sure if this pic will show the thru-hull very well. it's the only one I can find right now though. thruhull is in the bottom left hand side of the pic.
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Re: bronze to stainless?

#6

Post by Chaps » Mon Nov 10, 2014 7:46 pm

That's a Maxweld isn't it? Andy wouldn't have used bronze unless it was properly isolated from the hull.
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bigdogeh
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Re: bronze to stainless?

#7

Post by bigdogeh » Tue Nov 11, 2014 11:31 am

Yes, it's a maxweld (love the boat!).
Sounds like I should change over to stainless if it's less reactive. with the bronze at least the corrosion seemed to be concentrated on the bronze itself and not the aluminum. I would hope with stainless that the corrosion would be concentrated on the stainless rather than aluminum, but think it would be aluminum that would shed atoms... at least seems to be what i've seen when stainless fasteners are threaded into aluminum. I'll make sure I use plenty of locktite PTFE (liquid teflon tape) at the connections. (always wondered if this was basically the same as tef gel....)
thxs for your help Chaps!
bigD

Chaps
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Re: bronze to stainless?

#8

Post by Chaps » Tue Nov 11, 2014 2:42 pm

The corrosion issue between stainless accessories or fittings and bare aluminum from my observations is primarily with threaded fasteners, especially SS sheet metal screws into aluminum and that's where you want to use tef-gel. Teflon tape or pipe dope is suitable for threaded plumbing fittings in order to get better fluid sealing so they are very different products from Tef-Gel. Where your SS thru-hull fitting comes into contact with the alloy hull plating I would use a conventional bedding compound like Life Caulk. If your current thru-hull is bronze it is likely isolated from the hull with a non-metallic spacer or bushing and if that is in good shape you should re-use it along with fresh caulk. Tef-gel is not a caulk for thru-hulls. Personally I think the fibreglass re-enforced nylon (Marlon) fittings are the better thru-hulls for alloy boats if you want 100% prevention of galvanic corrosion. I also like alloy pipe welded in as a fitting.
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bigdogeh
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Re: bronze to stainless?

#9

Post by bigdogeh » Wed Mar 25, 2015 10:00 pm

ok,
just got back to this project and it looks like the thru hull is stainless itself with all bronze components. the threaded thru hull is threaded stainless with a 2" straight thread. the thin jam nut that sandwiches it to the hull and backing plate is bronze. then a 2" to 1-1/2" reducing coupling (bronze), bronze close nipple, then bronze 1-1/2 ball valve, and 1-1/2 bronze street elbow to 1-1/2 hose barb. from there it connects to the hose.
I've just removed everything off the thru hull from the !-1/2" reducing coupling to the street elbow... I noticed the reducing coupling on both sides was only holding on by a couple threads. this kinda makes sense since the thru hull is a straight thread and the reducing coupling npt (pipe thread)
how can I fix this situation? I'd like to replace everything with stainless if that is a better way to go but am worried about only having a couple threads holding. doesn't seem like a good situation with vibration in the engine room and the weight of the components being supported by only a few threads... :hammer:
looking for some help guys, :beer:
thxs
bigD

Chaps
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Re: bronze to stainless?

#10

Post by Chaps » Wed Mar 25, 2015 11:08 pm

A straight thread (NPS) thru-hull needs to be matched up with a flanged seacock valve with mating (NPS) straight threads on the bottom (input) side.

Flanged Seacock

Image

The principal is you tighten the seacock down to tightly sandwich the backing block between the seacock and the hull (with liberal application of sealant on everything) then put 3 lag screws through the base of the seacock into the backing block. After all that is secure and the sealant has fetched up then you can assemble pipe thread (NPT) components to the top of the seacock which will have the typical pipe thread (NPT) female outlet. That's how I was taught to do it anyway.

Or get a flange adapter which has the straight thread (NPS) on the bottom (inlet side) and pipe thread (NPT) on the upper side so you can attach pipe threaded elbows, valves, etc. The thin nut that holds everything together right now needs to be tossed.

Flange adapters

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bigdogeh
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Re: bronze to stainless?

#11

Post by bigdogeh » Wed Mar 25, 2015 11:28 pm

thxs Chaps!
well that makes sense now. So looks like maybe it wasn't put together properly to begin with. is there a reason all the seacocks I see online are made of brass? would it be OK to go with a stainless seacock? I may have a machinist make an adapter to go from straight thread to npt as I have a couple of 2" stainless valves here I'd like to use if possible. anyone know if there is anything already made like that? I probably won't be so lucky... I was wondering if the reason for using bronze was so that the bronze would shed electrons rather than aluminum... is that correct or would stainless be OK to use as a seacock and other components for the thru-hull? pretty sure the straight threaded part of the thruhull itself that goes thru the hull is stainless....

bigdogeh
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Re: bronze to stainless?

#12

Post by bigdogeh » Wed Mar 25, 2015 11:30 pm

looks like I was asking my questions while you were still editing and adding pics... Thxs. I see the question about a flanged adapter seems to be answered. Hopefully I can find one that is stainless if stainless is acceptable...

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Re: bronze to stainless?

#13

Post by Chaps » Wed Mar 25, 2015 11:56 pm

Flanged seacocks are bronze because its a great material for marine plumbing. Doubt you'll find them in SS and if you do they'll be big $$. Using bronze on your SS thru hull is not an issue IMO (its what you have now). Flanged seacock is much stronger than a ball valve on a nipple, just sayin'
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bigdogeh
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Re: bronze to stainless?

#14

Post by bigdogeh » Thu Mar 26, 2015 12:38 am

Chaps wrote:surprised to hear you've got a bronze thru hull on an aluminum boat. stainless would be way better as its fairly non-reactive (unlike bronze)

Hi Chaps, sorry but I guess I'm gonna bug you again... you seem to be the only one with an opinion on this and I appreciate your time!
In this post earlier you mentioned you were suprised I had a bronze thru hull on an aluminum boat. but after having a closer look today I noticed the threaded thru hull looks like it's actually stainless with bronze components sitting on top of it.
do you think it would be better to get the 2" bronze flanged adapter (nps to npt) for the stainless thru hull, or if you had a choice do you think it would be better to get a stainless flanged adapter (nps to npt)? I have a machinist friend who could prob make a couple for me... if I can't find them which I probably won't be able to... (assume that I could have them made though and money is no expense in that regard...)
If you suggest using the bronze flanged adapter, I assume I should stay with the original bronze components I removed?
thxs for your help. I just would like to do this properly. but if stainless is less reactive on an aluminum boat I would prefer to stay with stainless as I have most of the components at this time... just would have to have 2 flanged adapters fabbed or sourced...

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Re: bronze to stainless?

#15

Post by Chaps » Thu Mar 26, 2015 11:39 am

Again, as long as your bronze components are isolated from the hull via your SS through hull (and wood backing block) I don't see a problem and see no need to have custom SS adapters made. I would at least put on the bronze adapter to get rid of the NPS/NPT thread mismatch though personally I'd choose the flanged seacock as it is less susceptible to breaking off if some gorilla mechanic decided to step on your intake plumbing.
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bigdogeh
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Re: bronze to stainless?

#16

Post by bigdogeh » Thu Mar 26, 2015 1:01 pm

thxs for getting back to me Chaps,
I'll see what I can come up with...
in most installations do they try to isolate the thru hull with the hull? (skin) should there be no continuity between the thru hull and skin or does it not matter that much?
edit, that sounds like what you mentioned earlier but just want to make sure. I'll bring my continuity tester with me next time i'm at the boat...
hopefully my last question.
have a good one,
bigD

kmorin
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Re: bronze to stainless?

#17

Post by kmorin » Thu Mar 26, 2015 1:58 pm

Chaps, bigdogeh,

another way to solve the copper alloy issue in fitting on the hull is to create a SS seacock. http://www.nibco.com/Valves/Ball-Valves ... ISO-Mount/

By butt welding a short length of SS pipe to the flange that is mounted to the hull, and the other end to his (disassembled) 3pc. ball valve's butt weld end a 'no thread' joint is formed to the hull's SS plate and the valve's flange end. These valves or others like them are designed for hundreds psi service pressures and will stand rebuilding if the trim seats leaked (unlikely) so they represent an alternative means of putting a valve onto the hull without threaded connections.

Any SS used would serve best if it were passivated http://www.mmsonline.com/articles/how-t ... teel-parts, valves, caps screws, nuts, washers and flanges all become less subject to corrosion of both major types involved in through hulls.

I'm not discussing the cost of building this fitting stack -( not low) but I am suggesting there is a long term savings over having a patch of corrosion on your hull from the copper ions dripping off brass/bronze/copper in just normal condensate in the bilge; that saving alone is worth the effort IMO.

Just more to consider if you have someone to TIG some SS to this 3pc valve type's butt weld end piece.

Cheers,
Kevin Morin
Kenai, AK
kmorin

Chaps
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Re: bronze to stainless?

#18

Post by Chaps » Thu Mar 26, 2015 7:42 pm

bigdogeh wrote:thxs for getting back to me Chaps,
I'll see what I can come up with...
in most installations do they try to isolate the thru hull with the hull? (skin) should there be no continuity between the thru hull and skin or does it not matter that much?
edit, that sounds like what you mentioned earlier but just want to make sure. I'll bring my continuity tester with me next time i'm at the boat...
hopefully my last question.
have a good one,
bigD
Its not so much a question of continuity, the issue relates more to physical contact between metals with a high difference in nobility
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bigdogeh
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Re: bronze to stainless?

#19

Post by bigdogeh » Fri Mar 27, 2015 12:30 pm

kmorin wrote:Chaps, bigdogeh,

another way to solve the copper alloy issue in fitting on the hull is to create a SS seacock. http://www.nibco.com/Valves/Ball-Valves ... ISO-Mount/

By butt welding a short length of SS pipe to the flange that is mounted to the hull, and the other end to his (disassembled) 3pc. ball valve's butt weld end a 'no thread' joint is formed to the hull's SS plate and the valve's flange end. These valves or others like them are designed for hundreds psi service pressures and will stand rebuilding if the trim seats leaked (unlikely) so they represent an alternative means of putting a valve onto the hull without threaded connections.

Any SS used would serve best if it were passivated http://www.mmsonline.com/articles/how-t ... teel-parts, valves, caps screws, nuts, washers and flanges all become less subject to corrosion of both major types involved in through hulls.

I'm not discussing the cost of building this fitting stack -( not low) but I am suggesting there is a long term savings over having a patch of corrosion on your hull from the copper ions dripping off brass/bronze/copper in just normal condensate in the bilge; that saving alone is worth the effort IMO.

Just more to consider if you have someone to TIG some SS to this 3pc valve type's butt weld end piece.

Cheers,
Kevin Morin
Kenai, AK

interesting thoughts kmorin. I do have a few friends that are stainless tig welders. definitely food for thought. I'll get this sorted eventually. definitely won't be putting the npt valve onto the nps thru hull as it was originally. I'm just thankful that I hadn't had any issues with it like that in the past. that looks like a recipe for disaster. looking on the web (google) it's interesting to see how many people have done that and gotten away with it. and even reports of other boats coming from the factory (some big name builders) setup like that also... not good at all..

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