Need some quick Zinc/corrosion help and suggestions - Page 2 - SailNet Community
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post #11 of Old 01-25-2009 Thread Starter
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Cam, and SD - Thanks for the comments...I think I will be able to sleep at night now knowing this isn't something bad I was pretty worried for a while there.

SD - The zinc I was referring to IS on the outside in the water. I can see it from the dock if I bend down and look under the stern as the prop, shaft and zinc is visible. I am on my way down there again now. I bought one of those $50 grouper fish zincs and I am going to attach the wire to the shaft inside the boat and lead the fish zinc into the water for protection because I know the external zinc is shot.

Thanks again though

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post #12 of Old 01-25-2009
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Originally Posted by nk235 View Post

Ok so here is the update. I uploaded a picture of what the shaft looks so now that you can all see it firsthand, what do you think? Also I coudl see that the zinc on the shaft is very deteriorated and half missing so I know there is a problem some where.



[IMG][/IMG]
My main concern is with the hose clamps on the stuffing box hose. Replace those before you do anything! Also use AWAB non-perforated hose clamps when you do so..

Beyond that clean up the stuffing box & shaft with a brass brush and some Scotch-Brite. The box and shaft should be a uniform color with no splotches of a pinkish tinge.

Contrary to popular belief many marine bronzes do contain small amounts of zinc and can show signs of dezincification.

Tobin Bronze, what most marine shafting was made from, is generally 60% copper (Cu), 39% zinc (Zn) and 1% Tin (Sn). Tobin Bronze contains rather large amounts of zinc. If you are going to see dezincification it would more than likely be on the shaft rather than the stuffing box which is most likely a real bronze with a very low zinc content..

The difference between brass and bronze is essentially Zinc content. Brass is loaded with it and Bronze, real bronze, not Manganese or Tobin, do not, in content above 15%.

The main alloys of brass are, copper and zinc. The main alloys of bronze are copper and tin. The names of said alloys can cause lots of confusion as “Manganese Bronze”, what lots of props are made from, and “Tobin Bronze”, sometimes called naval brass, are actually alloys of 60/40 brass with about 1% manganese or 1% tin added. Even this little bit if Sn puts them in the bronze category instead of brass.??

These spots are dezincification of brass. It will look similar on a Tobin Bronze prop shaft..

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post #13 of Old 01-25-2009
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Exactly where are you seeing a zinc in this photo.
I don't think he was indicating that he was seeing a zinc in the interior end of the shaft. I think he was saying he noticed some corrosion on the inside (pictured above) and was hoping to be able to see the zinc on the shaft underwater (visibility permitting) and determine if it had been badly depleted or or not.

nk235, here are the web sites for a couple New York dive companies. One is based on Long Island, not sure about the other. Looks like you get a zinc installed for less than $100:

Boat bottom cleaning hull cleaning

BottomDwellers.net - In water cleaning,salvage and repairs
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post #14 of Old 01-25-2009 Thread Starter
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I cleaned up the shaft and stuffing box a bit and a lot of what I thought was corrosion just came off. Also when I was cleaning the shaft, I rotated it a little bit and then when I looked at the prop again from outside, low and behold I actually still hade my Zinc oops. I guess I couldn't see it for whatever reason yesterday and this morning so all and all I guess this post was really for nothing so I apologize. I am 24 so I know I have a lot to learn but I take great pride in careing for my boat and when I noticed this I freaked out. I did attach the fish grouper zinc with copper wire around the shaft just for peace of mind added protection. Again thanks to everyone who replied to help me out. Also those 4 rusted house clamps are being switched out this week.

Here is what it now looks like:

[IMG]Photobucket[/IMG]

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post #15 of Old 01-25-2009
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I'd hose clamp that wire to the shaft if I were you. Won't take much to make it lose whatever tenuous connection it has otherwise.
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post #16 of Old 01-25-2009 Thread Starter
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I'd hose clamp that wire to the shaft if I were you. Won't take much to make it lose whatever tenuous connection it has otherwise.
It actually is. You just can't tell from the picture but thanks anyway.

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The green corrosion is common on bronze, brass, and copper, and other such or smiler metals when in contact with air and water, The fact that your zink is gone in about five months is likely a result of being in the marina and your shore power connection. If you have or know someone that has a Amp clamp that will go around you shore cord you can check for AC current leeks on your vessel. You should see less then .03 or three one hundredths of an amp. It may be the near buy boats to, AC or DC.

The hose clamps need immediate attention
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