How scary is this? The white powder at the base of the thru hull is salt (from, I assume, an incredibly slow leak - no standing water is observed).
Thru Hull Corrosion
- Thread starter zds
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The scary part is no thru bolts in the flange base holes of that or the other one in the pic 
Without those bolts, it might be possible that the thru-hull can work and break the seal there. Not enough to dribble, but enough to let salt water creep in? Next time you pull it out, I would be sure to rebed and thru bolt those. . .
I will let others chime in if this would be considered an emergency
Without those bolts, it might be possible that the thru-hull can work and break the seal there. Not enough to dribble, but enough to let salt water creep in? Next time you pull it out, I would be sure to rebed and thru bolt those. . .
I will let others chime in if this would be considered an emergency
Yup. There are no bolts. Haven't been for >5 years, including one significant offshore passage and a great many inland (ICW) passages. That said, I do plan to correct that this winter...
But the corrosion is more on my mind. I assume this is simple seawater intrusion...
But the corrosion is more on my mind. I assume this is simple seawater intrusion...
Oh, okeydokey then
That was my thought though, no bolts allowed the seal to work a creeping leak into it. If you think it is salt, I would taste a little of it. I don't know of any chemical reaction with bronze that would produce white powder
As for the blue/green. . .I thought that was normal. All the thru hulls in my boat are solid blue/green except for the stuffing box which I cleaned and the 2 I replaced. And the stuffing box is slowly changing, as is the thru hull that sweats when the temp is right. The other thru hull is in the main cabin under a settee and not exposed to much stagnate moist air and is still bronze. As long as they don't turn pink I've been told. . .
That was my thought though, no bolts allowed the seal to work a creeping leak into it. If you think it is salt, I would taste a little of it. I don't know of any chemical reaction with bronze that would produce white powder
As for the blue/green. . .I thought that was normal. All the thru hulls in my boat are solid blue/green except for the stuffing box which I cleaned and the 2 I replaced. And the stuffing box is slowly changing, as is the thru hull that sweats when the temp is right. The other thru hull is in the main cabin under a settee and not exposed to much stagnate moist air and is still bronze. As long as they don't turn pink I've been told. . .
Just about all bronze includes at least a wee bit of zinc to enhance 'machinability', without the zinc the bronze becomes a 'btcih' to machine. The white powder is possible zinc oxide due to galvanic action attacking the zinc (using the wee zinc in the alloy as an 'anode'), the zinc has been extracted from the allow & has oxidized on the surface. Carefully remove the powder and scrutinize if that the base metal has become 'spongey-looking' or 'pink'; if yes, consider to replace immediately.I don't know of any chemical reaction with bronze that would produce white powder
If you can remove the component without marring or destruction and with all the 'clatter trap' of hoses, etc. removed, strike the side of the component with a small hammer --- if 'rings' when hit with a hammer its probably still intact bronze; if it sounds dead/dull when hit, its probably weakened (missing components of the alloy due to galvanic action) and should be replaced.
Such valves 'should' be connected to the bonding system and the bonding system be terminated with at least one independent (zinc or magnesium according to the salinity) anode. Without electrical bonding connection ultimately to a 'zinc', if electrolysis happens the wee bit of zinc will be removed from the alloy.
Once we hauled out the boat for a bottom job we replace all the thru-hulls.
We went from a catastrophe waiting to happen to a little mind at ease.
Just a little tap of a hammer broke the fittings.
Bub
We went from a catastrophe waiting to happen to a little mind at ease.
Just a little tap of a hammer broke the fittings.
Bub
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That seacock should be threaded tightly to the thru-hull fitting and likely not going anywhere. Follow Rich's advise and tap them lightly to test the metal. I have seen some just crumble. Getting off this issue it is recommended that you tie an appropitely sized wood plug to each thru-hull so in case of accidental failure you do not have to hunt for one. Drill a small hole at the end of the plug and tie with fishing line. Do not see a problem but test the metal periodically.
Your pics are an excellant visual aid to RichH brief on galvanic action. If you don't bond the new parts, it'll happen again.
Zinc eh? I learned something today
Also on things I've read, was to NOT bond thru hulls less they be electrically connected and potentially dissolve due to electrolysis. . .as long as they were isolated, there was no need. . .
Also on things I've read, was to NOT bond thru hulls less they be electrically connected and potentially dissolve due to electrolysis. . .as long as they were isolated, there was no need. . .
I appreciate the comments from all. Thanks.
I'm quite certain the white powder is salt, having tasted it. I also brushed the flange (as much as I could, given the space) and it shows a nice bronze color underneath. A picture is attached.
You can see the companion thru hull in the photo (the one with the corrosion is the lectrasan waste, the one without is the head seawater intake).
I suspect the corroded thru hull is simple experience a very minor leak from the lack of bolts, producing the salt deposit (I'm in brackish water) and the green...
I'm quite certain the white powder is salt, having tasted it. I also brushed the flange (as much as I could, given the space) and it shows a nice bronze color underneath. A picture is attached.
You can see the companion thru hull in the photo (the one with the corrosion is the lectrasan waste, the one without is the head seawater intake).
I suspect the corroded thru hull is simple experience a very minor leak from the lack of bolts, producing the salt deposit (I'm in brackish water) and the green...
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I have a Groco bronze sea chock that's about 15 years old. Never installed because it was the wrong size. It's been stored in the garage in a zip lock, yet there is a large dark green area of corrosion on it. It appears that the corrosion is superficial.
My sea cocks on the boat all have some green corrosion residue. From what I have read, one should scrape off the green stuff and look for pink spots on the metal. You will most likely only see pink, indicating major corrosion, on brass or low quality bronze.
My sea cocks on the boat all have some green corrosion residue. From what I have read, one should scrape off the green stuff and look for pink spots on the metal. You will most likely only see pink, indicating major corrosion, on brass or low quality bronze.
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