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Old 11-02-2015, 01:10 AM   #1
Join Date: Nov 2015
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Green discoloration of bronze thru hulls

Hello boaters

My boat has green discoloration of all its bronze thru hull
They are unsightly. Is this a form of corrosion?
Or just oxidation of the metal

Is it not desirable ?

What are the downside to leaving it as is?

Thx in advance

Marina deal Rey CA

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Old 11-02-2015, 03:24 AM   #2
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Nothing to worry about Spaniards have had the same problem for many years with their ear rings

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Old 11-02-2015, 03:37 AM   #3
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Welcome aboard! Green is OK, pink is bad.
1984 Monk 36 Hull #46
Englewood, FL and Cape May, NJ
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Old 11-02-2015, 05:44 AM   #4
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Welcome aboard. Well, from what I remember from chemistry 101, oxidation IS corrosion (as a general statement). That green coating is called verdigris and is not terribly harmful. https://en.wikipedia.org/wiki/Verdigris
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Old 11-02-2015, 09:26 AM   #5
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Agree totally with High Wire , all good


Cheers Chris D Liberty Australia
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Old 11-02-2015, 10:15 AM   #6
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Can come from leakage, that's sort of bad. Or just condensation, which is normal. You can clean them up and spray with a corrosion block.
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Old 11-02-2015, 02:11 PM   #7
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You can use a product called Boeshield to stop the green corrosion. I am told it was developed by Boeing for aircraft corrosion control. The fumes are quite strong so you can only do a small amount in an engine room or lazererette at one time, but it works great. It will spread to the back side of a fitting that has been sprayed.
Tucker Fallon CPYB
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Old 11-03-2015, 05:31 AM   #8
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IF the bronze was factory polished to a smooth finish , polishing it is worth while.

IF its just a cast item , green is good enough,
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Old 11-03-2015, 07:42 AM   #9
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The green is not the concern. Its the color of the thru hull under the green. If the metal under the green is pink that is not good. It means the zinc in the metal has been used up weakening the thru hull which. So the green alone is not the primary factor.
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Old 11-03-2015, 08:25 PM   #10
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Salt water turns the thru hull green over time.
To bring the metal back to the original color, getting rid of all the green, wrap the fittings with Scott towels soaked in white vinegar and let it set. Come back and dampen them again and just wait. After a while all the green will be gone.
If you have areas of the boat that have a smell, just leave a small bucket or Tupperware half full of white vinegar in that area and the smell will soon be gone.

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