I’m replacing the rudder on my (new) Typhoon. Nauset Marine made the new rudder with a stainless steal pin, but it looks like the gudgeon is brass. Should I be worried about galvanic corrosion of the gudgeon? Would putting a zinc on it help? The gudgeon is fiberglassed into the keel, so replacing would be a lot of work.
Thanks,
--Bill
b4usail@aol.com
Brass Gudgeon/ S.S. pin - galvanic corrosion ?
Moderator: Jim Walsh
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matt cawthorne
Re: Brass Gudgeon/ S.S. pin - galvanic corrosion ?
Bill,
I am not familiar with the details of the gudgeons on the Typhoon so take from this post what applies to you and ignore the rest. If they are below the water line then a zinc would be essential. Better yet, get the pintles changed to bronze. If they are above the water line then adding a zinc will do no good unless you actually plate the gudgeons.
Brass or Bronze? Be careful here. Brass is copper with zinc as the primary alloying element. Brass can dezincify, particularly below the water line. The catch here is that when brass dezincifies it gets weak even though it has the same shape that it did when it was new. It's color tends to get more red.
Bronze is a copper with tin as the main alloying element. It does not get weak unless the material is wasted away. Bronzes tend to be a darker color when new. Brass is much more yellow.
To add to the confusion there are several brasses that have the word bronze in their name. "Tobin Bronze", and I believe "manganese bronze" are two of the brasses that have misleading names.
For what it is worth, Spartan tended to make things in Bronze and I suspect that the gugeons on your boat are no exception. If the original pintles were bronze, then I would try and get them changed unless you know for some reason that the originals were unacceptable.
good luck,
Matt
mcawthor@bellatlantic.net
I am not familiar with the details of the gudgeons on the Typhoon so take from this post what applies to you and ignore the rest. If they are below the water line then a zinc would be essential. Better yet, get the pintles changed to bronze. If they are above the water line then adding a zinc will do no good unless you actually plate the gudgeons.
Brass or Bronze? Be careful here. Brass is copper with zinc as the primary alloying element. Brass can dezincify, particularly below the water line. The catch here is that when brass dezincifies it gets weak even though it has the same shape that it did when it was new. It's color tends to get more red.
Bronze is a copper with tin as the main alloying element. It does not get weak unless the material is wasted away. Bronzes tend to be a darker color when new. Brass is much more yellow.
To add to the confusion there are several brasses that have the word bronze in their name. "Tobin Bronze", and I believe "manganese bronze" are two of the brasses that have misleading names.
For what it is worth, Spartan tended to make things in Bronze and I suspect that the gugeons on your boat are no exception. If the original pintles were bronze, then I would try and get them changed unless you know for some reason that the originals were unacceptable.
good luck,
Matt
Bill McMahon wrote:
I’m replacing the rudder on my (new) Typhoon. Nauset Marine made the new rudder with a stainless steal pin, but it looks like the gudgeon is brass. Should I be worried about galvanic corrosion of the gudgeon? Would putting a zinc on it help? The gudgeon is fiberglassed into the keel, so replacing would be a lot of work.
Thanks,
--Bill
mcawthor@bellatlantic.net
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Bruce Lumsden
Re: Brass Gudgeon/ S.S. pin - galvanic corrosion ?
Bruce LumsdenBill McMahon wrote: Bill- I have an older CD 25 whose rudder armature/heel bearing is similar to that on the Typhoon. I would be very surprised if Spartan made a brass heel bearing. I completely rebuilt my rudder a couple of years ago, reusing the stainless armature/pintle and heel bearing. I found no signs of dezincing on the heel bearing and pounded on it pretty hard while peening over the pins with which the heel bearing is fastened...not a sign of problems. I suppose it can't hurt to add sacrificial anodes, being careful not to puncture the voids around the moulded-in ballast. Hope this is helpful.
CD25 'Sabine'
Hull 312
Harpswell, Maine
Bill McMahon wrote: I¹m replacing the rudder on my (new) Typhoon. Nauset Marine made the new rudder with a stainless steal pin, but it looks like the gudgeon is brass. Should I be worried about galvanic corrosion of the gudgeon? Would putting a zinc on it help? The gudgeon is fiberglassed into the keel, so replacing would be a lot of work.
Thanks,
--Bill
JLumsden@gwi.net
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matt Cawthorne
Configuration
Bill,
If the Ty has the same rudder configuration as the larger CDs then the stainless shaft in a bronze shoe is perfectly acceptable. The bronze shoe does protect the stainless rudder shaft, but there is not much stainless area exposed so the amount of material that is lost each year is very minimal. In addition the bronze does not have a weakening problem like brass does under water. Eventually the shoe will disolve away, but the rate is so low and the fitting so heavy that it will not be a problem in our lifetime.
Matt
mcawthor@bellatlantic.net
If the Ty has the same rudder configuration as the larger CDs then the stainless shaft in a bronze shoe is perfectly acceptable. The bronze shoe does protect the stainless rudder shaft, but there is not much stainless area exposed so the amount of material that is lost each year is very minimal. In addition the bronze does not have a weakening problem like brass does under water. Eventually the shoe will disolve away, but the rate is so low and the fitting so heavy that it will not be a problem in our lifetime.
Matt
mcawthor@bellatlantic.net