Cast iron keel

[Mechone]

For past 2 years after haul out I have had rust coming thru micron on keel , my buddy with his 375 first too. Hours of sanding and painting on 2000e epoxy coat
Last year we both installed 2 zincs on keel before launch teardrop style. Haul out today, both of us had no rust on our keels

 

[Daveinet]

If you sanded it, you did it the hard way. Grinding or sanding takes way too much time to remove the pitting. If you sand blast it, it will get rid of the rust, and not take off anywhere near as much metal. The surface will be rough but that can be fixed with paint. On my keel, I used Cold Galvanize paint. It has worked fairly well, although it does wear off after a while.

 

[Bob S]

I'm curious how you mounted a zinc on your keel? Any pictures?

 

[BrianRobin]

If you sanded it, you did it the hard way. Grinding or sanding takes way too much time to remove the pitting. If you sand blast it, it will get rid of the rust, and not take off anywhere near as much metal. The surface will be rough but that can be fixed with paint. On my keel, I used Cold Galvanize paint. It has worked fairly well, although it does wear off after a while.

Are you in fresh or salt water ?

 

[fstbttms]

Anodes do not combat oxidation

 

[Mechone]

Anodes do not combat oxidation

If the surface coating of paint is scratched rusting will take place immediately. This is not the preferred method of rust prevention for giant ships that often scrape against rocks, sand and barnacles. Instead, a sacrificial anode is used. A sacrificial anode is a block of metal that is more reactive than iron.
In other words you are totally wrong and I have 2 boats to prove it. Our boats are in fresh water Lake Ontario, however it should not matter. I have a winged keel and mounted them on the wing either side narrow part of tear going forward to cut thru water, my buddy no wing just mounted either side of keel small end of tear going forward

 

[BigEasy]

Are you sure that you were not having problems with galvanic corrosion on your cast iron keel instead of an oxidation problem?

 

[Mechone]

This is the style I used ,drilled and tapped 1/4 -20 316ss cap screw , I actually used zinc which ate away a bit ,my buddy used Magnesium which is for fresh water which ate more than the zinc

 

[fstbttms]

If the surface coating of paint is scratched rusting will take place immediately. This is not the preferred method of rust prevention for giant ships that often scrape against rocks, sand and barnacles. Instead, a sacrificial anode is used. A sacrificial anode is a block of metal that is more reactive than iron.
In other words you are totally wrong and I have 2 boats to prove it. Our boats are in fresh water Lake Ontario, however it should not matter. I have a winged keel and mounted them on the wing either side narrow part of tear going forward to cut thru water, my buddy no wing just mounted either side of keel small end of tear going forward

Well, I guess you learn something every day and I stand corrected. That said, you should've indicated that the words you posted were not your own and provided a link to the quote you used.

 

[Mechone]

Are you sure that you were not having problems with galvanic corrosion on your cast iron keel instead of an oxidation problem?

Impossible ,first my keel like most Beneteau's is not grounded both of us have gas charged lightening arresters that were installed by beneteau, secondly I was grounded thru the drive shaft ,but I installed a flexible coupling that isolates the drive from transmission and thirdly I have a Galvanic 150amp isolator on board that has Leds that show any leakage AC or DC . Before I installed the Isolator and coupling the anode on drive shaft would pit, this year it still looks like new