I read in a sailing article the other day that you must be careful to insulate stainless steel fittings on aluminum spars or the aluminum will corrode. I don't know anything about this but after reading this I noticed that all the corroded areas on my anodized aluminum mast are all near attached stainless steel hardware. Can anyone explain this phenomenon in more depth and explain what to do about it? Thanks.
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Paul Cossman
corrosion
I am not the one to explain any details about galvanic corrosion, but I am certainly familiar with its results. It doesn't only affect stainless/aluminum, but will also affect stainless/bronze and stainless/brass. For example, Hunter decided to use a bronze nipple fitting on my aluminum holding tank on my 1991 P42. It eventually corroded a 1-1/2 inch hole in the holding tank. Lucky it didn't sink the boat. The easiest answer on the corrosion you face on your mast is to use an anti-seize lubricant. Apply it liberally on all fittings you use on your mast. I have used it on stainless steel bolts that I have tapped into my mast, and it has retarded corrosion significantly. If your boat has an aluminum toerail, you may want to take a look at the corrosion where the stainless steel bolts are located on the toerail. You can also work to retard that corrosion by applying a protectant like Boeshield or something similar.
I am not the one to explain any details about galvanic corrosion, but I am certainly familiar with its results. It doesn't only affect stainless/aluminum, but will also affect stainless/bronze and stainless/brass. For example, Hunter decided to use a bronze nipple fitting on my aluminum holding tank on my 1991 P42. It eventually corroded a 1-1/2 inch hole in the holding tank. Lucky it didn't sink the boat. The easiest answer on the corrosion you face on your mast is to use an anti-seize lubricant. Apply it liberally on all fittings you use on your mast. I have used it on stainless steel bolts that I have tapped into my mast, and it has retarded corrosion significantly. If your boat has an aluminum toerail, you may want to take a look at the corrosion where the stainless steel bolts are located on the toerail. You can also work to retard that corrosion by applying a protectant like Boeshield or something similar.
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R.W.Landau
Corrosion
Aluminum is a very durable material. It does have it's downfalls. The mast was anodized when it was first made. This anodized coating helps to protect the aluminum from harmfull corrosion. It fails to function thru time. You can help it wear better by waxing it anually. Another way is to apply Marine Penitrol. This discolors the mast a bit but if applied evenly it is not noticable. If the mast is very bad already, a coat of good paint is the best protection. The corrosion is cause by electrolisis. The salts from the water attack it and the dissimilar metals cause some electrolisis. If you see a white powdery material or pits with white edges, this is the corrosion. If it is very severe, have someone look at it to make sure that there is not a structural problem. I like to make sure that the surface behind the fitting is in good shape. Then use nolox on the threads of the fasteners before installing them. Nolox, normally a gray cream that is used in electrical applications when joining aluminum to copper or steel connection in a electric panel. It is also used in automotive applications when connecting steel bolts into and aluminum head. The material helps to prevent galvanic action (Electrolisis) from occuring. Thats all I can tell you. Maybe someone else can suggest a better barrier between the metals. r.w.landau
Aluminum is a very durable material. It does have it's downfalls. The mast was anodized when it was first made. This anodized coating helps to protect the aluminum from harmfull corrosion. It fails to function thru time. You can help it wear better by waxing it anually. Another way is to apply Marine Penitrol. This discolors the mast a bit but if applied evenly it is not noticable. If the mast is very bad already, a coat of good paint is the best protection. The corrosion is cause by electrolisis. The salts from the water attack it and the dissimilar metals cause some electrolisis. If you see a white powdery material or pits with white edges, this is the corrosion. If it is very severe, have someone look at it to make sure that there is not a structural problem. I like to make sure that the surface behind the fitting is in good shape. Then use nolox on the threads of the fasteners before installing them. Nolox, normally a gray cream that is used in electrical applications when joining aluminum to copper or steel connection in a electric panel. It is also used in automotive applications when connecting steel bolts into and aluminum head. The material helps to prevent galvanic action (Electrolisis) from occuring. Thats all I can tell you. Maybe someone else can suggest a better barrier between the metals. r.w.landau
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GARRY @ S/V TASHTEGO
SS-Al Corrosion
I mounted a stainless based turning block on the end of my boom for the outhaul. Pretty soon rust was forming on the boom below the block. I removed the block, cleaned off the rust and made an eighth inch thick mounting pad from starboard (a plastic board available at West Marine and other stores) and reinstalled the block using Tefgel (TM) antisieze compound. No more problems. Just coating the fasteners was not enough when a stainless base plate was mounted on aluminum. Tefgel on the bottom of the SS plate might have been enough but I had a small piece of starboard left over from another project and felt it was a sturdier solution.
I mounted a stainless based turning block on the end of my boom for the outhaul. Pretty soon rust was forming on the boom below the block. I removed the block, cleaned off the rust and made an eighth inch thick mounting pad from starboard (a plastic board available at West Marine and other stores) and reinstalled the block using Tefgel (TM) antisieze compound. No more problems. Just coating the fasteners was not enough when a stainless base plate was mounted on aluminum. Tefgel on the bottom of the SS plate might have been enough but I had a small piece of starboard left over from another project and felt it was a sturdier solution.
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Brian Pickton
Rusting away again in ....
Dec.5, 2000 Dear Anthony, You've gotten some good advice from the other posts sent in response to your querry. For further information on galvanic action, any well written modern boat building text covers the topic, especially in the steel and aluminum boat building field. Check them out of your local library. Your going to have to dismount the hardware and isolate it mechanically from the mast. That means remounting it on a non - conductive base plate and isolating the fasteners using one of the insulating creams that have been recommended. Don't delay getting this done because the cost of repair or replacement can be horrendous if the galvanic process gets too far advanced. Structural damage to the mast can occur which can lead to the mast collapsing. Good luck with the project , and while your at it may I refer you to J. Cherubini's post on dealing with inanimate objects? Brian Pickton@BeneteauOwners.net Aboard The Legend, Rodney Bay, St. Lucia
Dec.5, 2000 Dear Anthony, You've gotten some good advice from the other posts sent in response to your querry. For further information on galvanic action, any well written modern boat building text covers the topic, especially in the steel and aluminum boat building field. Check them out of your local library. Your going to have to dismount the hardware and isolate it mechanically from the mast. That means remounting it on a non - conductive base plate and isolating the fasteners using one of the insulating creams that have been recommended. Don't delay getting this done because the cost of repair or replacement can be horrendous if the galvanic process gets too far advanced. Structural damage to the mast can occur which can lead to the mast collapsing. Good luck with the project , and while your at it may I refer you to J. Cherubini's post on dealing with inanimate objects? Brian Pickton@BeneteauOwners.net Aboard The Legend, Rodney Bay, St. Lucia
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Robert Fischer
old tire tube
I use an old bicycle tire tube cut to size for each area. It's thin and doesn't compress too much. It works very well. Always add something to the threads also. Good luck.
I use an old bicycle tire tube cut to size for each area. It's thin and doesn't compress too much. It works very well. Always add something to the threads also. Good luck.
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