Corrosion on bronze through-hulls?

[Peregrine1983]

Hey all, curious to hear your input. The previous owner installed all new beautiful bronze Perko through hulls shortly before he sold the boat to me.

There are several on the boat (1983 Pearson 424). During the survey it was flagged that none of these new through hulls had been electrically bonded. The old bonding wire was just laying next to all the through hulls and had been cut and never re-attached.

I went over the whole boat with brand new 8GA wire and bonded every through hull to the motor and thus the negative ground on my electrical system.

There was a tiny bit of green oxidation (?) on the through hulls before I bonded them. I figured that this would stop once I bonded everything. The oxidation seems to be spreading on some of them. Is this just normal for bronze (IE the Statue of Liberty), or do I have a bonding problem?

[Cheechako]

Green oxidation is normal on bronze. There is a running debate on bonding or not bonding. I'm a bit in the "not bonding" camp. If you are not bonded then you wont have them effected by other things in the boat.
If the boat had new thru hulls and the bonding cut that would tell me something.

[Peregrine1983]

Originally Posted by Cheechako

Green oxidation is normal on bronze. There is a running debate on bonding or not bonding. I'm a bit in the "not bonding" camp. If you are not bonded then you wont have them effected by other things in the boat.
If the boat had new thru hulls and the bonding cut that would tell me something.

I hear ya... Thanks

[roverhi]

There is some controversy whether bonding is worth the hassle and some think it's detrimental. Have had two boats without bonding and they were fine. Two boats with bonding. One was fine and the other had serious electrolysis issues that we weren't able to solve. Fortunately it was just with the C/B cable so more of a nuisance than a fatal flaw.

As far as the green stuff, believe it's called verdigris and is a normal oxidation on brass/bronze/copper. The oxidation actually protects the metal from corrosion. What you don't want to see is bright metal with a pinkish tinge, that's electrolysis

[malyea]

Originally Posted by Cheechako

If the boat had new thru hulls and the bonding cut that would tell me something.

What would it tell you?

[MarkSF]

The problem with bonding is that it is fine with everything connected properly. But if a connection fails, you can accelerate corrosion by having through hulls connected together, but not to the engine.

[MarkSF]

Originally Posted by malyea

What would it tell you?

That someone liked new through hulls, but didn't like bonding

[rwidman]

Originally Posted by MarkSF

That someone liked new through hulls, but didn't like bonding

Or that they forgot to finish the job.

[Cheechako]

Originally Posted by malyea

What would it tell you?

Nothing definite really, but it could indicate a previous problem also... if the first thru hulls lasted 30 years, why cut the bond?

[Blue Stocking]

Guarantee me that EVERY piece of bronze exposed to the water is the exact same alloy, and I'll go along with not bonding. Until then, Bond.

[wrwakefield]

Separate from the bonding question... We spray all our bronze through-hulls, valves, etc. that are inside the hull with Corrosion-X and never have any corrosion build-up.

Spray a light coat. Wipe up the excess that drips onto the hull interior. Repeat every 5-10 years, or whenever you install a new, or wipe all the C-X off a fitting...

In case this is also of interest.

Cheers! Bill

[Cadence]

Originally Posted by Blue Stocking

Guarantee me that EVERY piece of bronze exposed to the water is the exact same alloy, and I'll go along with not bonding. Until then, Bond.

That is something I hadn't heard before. Basically your speaking of it creating a battery. I'm not sure the difference in alloys would be significant enough to cause deterioration in the short term less that twenty years?

[Elie]

Strangely, I discovered a baffling problem regarding corrosion. On my boat, the external ground(for 110 ac) consist of plate of what I presume is bronze, a large zinc anode, trough bolted with stainless steel bolts(2) and nuts . One of the bolt serves as a post for the AC ground(green wire). My Volvo Engine MD22L is ground insulated. That post nut is completely corroded and crumbling. The bolt to witch it is attached, and the other bolt are perfect. I hardly use shore power.
Any explaination?. Is this having to do with a poor quality nut, or some strange galvanic corrosion? Baffled!

[zeehag]

green is good pink is bad.
green is also patina.
pink is sick electrolyzed unreliable remnants.