Green on the through hulls

[Doghouse]

I was a bad boy and did not change my zincs early enough, and when I went under there was nothing there. Since then I have put on new zincs. The green has not spread on the through hulls, but is it ok to leave them a little green, or should I clean them back to shiny and new? I plan to re-check everything soon to make sure all is good.

[colemj]

I have to make some assumptions here, so I am assuming you are refering to your shaft zinc and bronze through hulls.

The green on the through hulls is the normal patina associated with bronze oxidation and is not a symptom corrosion. So you are fine here. Corrosion damaged bronze will turn pinkish and become spongy as any zinc in the casting alloy is eaten away. Most quality bronze will not readily undergo this damage.

The shaft zinc is protecting your propellor and shaft and, possibly to some extent, components of the engine/transmission. The exception is if you have your through hulls bonded to the engine. Then the zinc will also be sacrificial for them.

I think you are fine and do not need to worry about the green through hulls.

Mark

[Doghouse]

Thanks I was freaking out a little thinking I had messed up bad and was going to have to replace them... Big $$$$ flashing infront of my head

[Wahoo Sails]

The Green is actually a layer of oxidization that is beneficial to the bronze. The customary test is to scratch the thru hull with a pocket knife, if it looks like gold you're fine, if it looks pink the zinc has leached out & you're in need of replacement.
Bob