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Need to reattach a bronze (brass?) hold down plate in the bilge. It's not submerged in seawater. Originally secured with a bronze 1/4' bolt & nut. The nut vibrated off and is now lost. My neighborhood hardware store does not carry brass fasteners but said stainless & Bronze are compatible. I can either go with SS locking nuts or SS bolt & nut without issue.
Thought I'd run it by the forum. Is brass/SS OK?
Last edited by Passages; 03-27-2006 at07:40 AM
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In general brass is more subject to corrosion than bronze. You should be able to get a bronze nut from a marine supply store. It's preferable to retain all bronze with bronze components if that's what was original. You can use marine stainless, but that's less desireable with bronze components. Defender and Hamilton Marine online likely sell marine bronze nuts...you want silicon bronze....as original.
I should have mentioned: If the hold down plate is not regulalrly in bilge nor other water likely a brass nut will last many,many years....
Bronze, brass and stainless are all compatible. Your prop shafts are stainless, your props are bronze or brass. They connect directly to each other.
The concern is where there can be a current passing through or between them if they're in salt water...then galvanic action will corrode the more susceptible of the two metals. Particularly since yours is not regularly in salt water, any of them will do just fine.
Doug Shuman
Brass (bronze, whatever, it's made of copper) and stainless are NOT compatible in an electrolyte. We get away with it re our props and shafts only because there is a sacrificial anode (zinc) that is less noble than either of the other metals, and sacrifices (ionic flow to the more noble metal) thereby protecting the shaft/prop. If you combine ANY unlike metals in an electrolyte without a sacrificial anode you're asking for trouble. Even combining two different alloys of stainless (304/316/316L) in seawater is a problem.
Stick with bronze nuts on bronze bolts/parts.
"The older I get, the faster I was......."
1979 60C "Ohana" hull# 331
He said it's not in seawater.
For the purposes of corrosion, anything on a boat must be viewed as if it were in seawater to some extent, as it lives in a very humid invironment, so there is always some ionic flow between the dissimilar metals. That's why the connectors on the back of your salon TV corrode.
"The older I get, the faster I was......."
1979 60C "Ohana" hull# 331
I am little confused on this subject. Recently, I changed out the impellor on my raw water pump (Johnson pump). When I went to put the cover plate (which is stainless steel) back on the pump (which is bronze), I broke the head off one of the screws and could not get a replacement in bronze. I did replace it with stainless steel. My question is, if the pump cover plate is stainless and the pump itself is bronze, is there a problem with stainless screws holding the cover plate to the pump? BYW, I am in saltwater.
George
Yes, there's a problem with it, but if you assemble the parts with grease smeared on everything, it will likely be ok even though it's wrong. Remember, almost nothing in this world is really done "right".
"The older I get, the faster I was......."
1979 60C "Ohana" hull# 331
The corrosion resistance is highest with stainless, then bronze with brass last. I'd go with the stainless fastener. If there is any corrosion it will be on the plate, which is probably thick enough that it won't be a problem. A brass nut will corrode off in no time at all. Notice how brass always needs polishing but bronze statues are around forever? A brass nut will turn into a green crusted crumbly copper nut real quick. If the parts were under water I'd spend some time looking for bronze but stailess is ok for this.
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Join Date: Aug 2008
04-30-2016, 10:22 PM Reply
I want to use a stainless steel ball valve ( http://amzn.com/B00O5D1ERG ) at the point where my heater hose connects to my engine. There are already some bronze (I assume... guess they could be brass) fittings in the current valve-less connection, and I'd like to keep those - especially since one of the parts I couldn't find in stainless steel anywhere. (I could get a bronze valve, but it actually costs more and will take longer to ship.)Is there any problem with connecting bronze to stainless steel above the waterline, but with (hot) water going through the connection? Corrosion is my concern. I'm guessing it's probably okay, since a bronze/brass fitting is currently connected to the port on the engine.Thanks...
Join Date: Nov 2006
04-30-2016, 11:43 PM Reply
That is 304 Stainless and it should not be affected by the bronze or brass it is in contact with but it may cause some increase in the corrosion in the bronze. That's more important if you are in brackish or salt water. I would put connect it in my own boat but it would be worth checking after the first season and occasionally after that. The corrosion properties are very tough to get an accurate reading on as you need to know exactly what the components of the alloys are and how conductive the water is. It should be better than the connection with cast iron.
I am not an expert in metallurgy..
Join Date: Aug 2008
05-01-2016, 8:07 AM Reply
Thanks for the info.I decided to play it (hopefully) safer and paid more for a bronze valve: http://www.pbsboatstore.com/apollo-b...-way-valve.htm After reading about corrosion between different kinds of metals, I felt slightly concerned about the brass connection to the cast iron engine housing, since apparently brass will corrode cast iron only slightly less than that 304 stainless steel ( http://www.ssina.com/corrosion/galvanic.html ).
Join Date: Aug 2014
05-05-2016, 8:34 PM Reply
The fittings you are talking about are brass not bronze(similar but different)
As a piping engineer that designs , builds and sells high pressure(up to 150,000PSI) systems for subsea and offshore oil and gas platforms, I can tell you that there is absolutely NO issue with combining Brass and Stainless in your situation.
There is also NO corrosion issues as mentioned above. Stainless steel is actually LESS corrosion resistant to Chlorides(salt water NaCl) than brass. The above statement by Art is false in regards to any type of increase in corrosion resistance.
VERY IMPORTANT!!!
When installing your SS fittings into your SS valve you MUST use some sort of thread sealant/compound(teflon tape or pipe dope) to prevent gauling and to ensure a seal as the threads are tapered. This includes opening up the box and test fitting the fittings in your hand. Just by hand tightening the two SS fittings in your hand, you can cause gaulling. Gauling is basically the fittings welding themselves together in your hands in ambient room temp. You will NEVER be able to take them apart once they gaul.
Join Date: Aug 2008
05-05-2016, 8:39 PM Reply
Thanks for that info Mark!
I'm definitely going to use teflon tape, but I hadn't heard about gauling... very good to know.
Join Date: Nov 2006
05-05-2016, 8:50 PM Reply
Thanks Mark I always appreciate specific knowledge.
Join Date: Aug 2014
05-05-2016, 8:54 PM Reply
Thanks for not taking that personally Art!!!! I only wanted to clarify things for the original question.
Join Date: Aug 2014
05-05-2016, 9:02 PM Reply
Interesting thing about galling.....
If you were to hand screw the brass fitting into an SS fitting, it cannot gaul
I have literally seen it hundreds of times when a rig hand test fits some fittings(of the same SS material) in their hands, not even tightened, just loosely assembled, and spends hours and uses cheater bars to try to separate them again. They will never come apart.
Join Date: Jan 2004
05-08-2016, 9:19 AM Reply
Interesting too that it's galling not gauling...gall not gaul. Of course this may be galling to some.
Join Date: Oct 2007
05-08-2016, 2:52 PM Reply
I will share what I have learned while being in the marine biz. Proper marine plumbing fittings are indeed bronze, and quite different then the brass fittings you find at the hardware store. You can get some reaction between dissimilar metals such as bronze and stainless. I do not suggest brass residential and commercial plumbing fittings from the hardware store, for your boat. For a freshwater trailer boat, I doubt you would ever see an issue with a bronze and stainless mating. Different story for a wet-slip boat or one used in salt or brackish waters.
Join Date: Aug 2014
05-09-2016, 9:21 AM Reply
Quote:
bftskirOriginally Posted by
Interesting too that it's galling not gauling...gall not gaul. Of course this may be galling to some.
Damn autocorrect...
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