Keel Electrolysis on Bavaria Vision 46

[Kibo]

Hi, does anyone have experience of cast iron keel corrosion apparently caused by electrolysis on any Bavaria? My 2014 V46 was in the water at a marina in the Caribbean for almost two years with the original epoxy osmosis barrier and antifouling and has had some of the epoxy coating "blown" off the keel. The keel trailing edge is also pitted showing evidence of corrosion. She was hauled once for cleaning during that time

She is currently on the hard undergoing inspection and testing but if anyone has experience please let me know any thoughts and possible remedies. I have had one or two suggestions as to cause: poor marina power grounding, internal leakage current. One suggestion as to remedy: fit extra anodes directly to the cast iron keel.

Thoughts please?

[Symphony]

Highly unlikely it is galvanic corrosion as the keel is cast iron and not connected with any other metals under water. What you have is probably straightforward rust, perhaps with some local imperfections in the casting causing local pitting. Anodes will not do anything to help. The only long term solution is to blast back to bare metal and coat with epoxy again. Alternatively, do what most people do and carry out local repairs to the surface every time you haul out.

Nothing to do with marina power grounding, nor with any internal electrical leakage as the keel is not electrically connected to either the AC or DC system.

[Kibo]

Thanks Symphony.

I am having the keel blasted and re-epoxied/antfouled before launch in November but wanted to make sure it was not going to end the same way when I haul again 6 months later....

I had several conversations with folks in the yard when we hauled in April (mostly owners) and I had assumed that as you say it was simply poor adhesion to the cast iron and re coating would solve it; it was worse on the "sunny side" of the hull since we spend much time at anchor or on moorings in the Easterly trade winds so I figured that maybe was the cause.

The subject of galvanic corrosion came up during those conversations and again now with the contractor I am using to do the bottom paint etc. 

I have a follow up question for you, you state that there is no electrical connection to the keel which I understand in terms of individual pieces of electrical equipment, however there is a grounding strap attached to the keel bolts which I assume is for possible electrical storm lightning strike grounding? I have traced this back to the house battery ground wire. I assume it is a standard Bav fit since the boat is new in 2014 and although I have added solar panels and wind generator in 2016 I did not have this strap added or cahnged. Would this transfer any possible leakage through to the keel? Should I disconnect this perhaps? Thanks again for any comments

[Lyra]

I am not sure what the reason for it is, but I also noticed this situation when the boat was lifted out 4 years ago, when 2 years earlier there was no sign of any corrosion.
After fixing all the pits I fitted anodes directly on the keel and they do get gradually "eaten" (and the keel since installation did not get any additional corrosion).
It is a simple fit so I think worthwhile if  you are not sure what the cause is.

[Harveyhall]

I am new to Bavaria's but just went through major refit before I purchased the boat 3 months ago. The bottom was sand blasted on the 2005 36 Cruiser. The keel pitted was filled and was sealed with a barrier coat then complete bottom was then reepoxed with 4 coats and 2 coats of bottom paint.

The rudder bearing housing was replaced due to Electrolysis. The Steering wheel was not only very stiff to turn but after close examination the lower bearing housing was badly corroded on exterior and almost starting to leak evident by salt crystals on the boat interior. As far as I could see the electrolysis of the aluminum caused swelling squeezing the nylon (or some composite) bearing to the point where it needed to be cut out of the housing.

After research into aluminum bearing housing both from respected marine surveyors and Jefa Rudder Bearing (http://www.jefa.com/electro-f.htm ) copper based bottom paint used overtop aluminum bearing housing, turns the boat into a metal boat and the rudder bearing housing in to an anode. (of course the same goes for aluminum sail drives if they were to be painted.)

I stand corrected if I am wrong.  Many of you have much more experience in this area. I will be interested in your comments.

[tiger79]

After research into aluminum bearing housing both from respected marine surveyors and Jefa Rudder Bearing (http://www.jefa.com/electro-f.htm ) copper based bottom paint used overtop aluminum bearing housing, turns the boat into a metal boat and the rudder bearing housing in to an anode. (of course the same goes for aluminum sail drives if they were to be painted.)

Yes, copper-based antifoul shouldn't be used on or near the rudder bearing or stock.

[Kibo]

Thanks Lyra. I think anode fit is what I will do   Can I ask is your keel grounded like mine is? Symphony said the (his?) keel is not attached to either the DC or AC systems but mine is definitely bonded to the neg terminal of the house bank. Also were you more in a marina or out swinging on the hook when you noticed the corrosion? Thanks again for your help.

[bobvee]

Hi Kibo

Did you end up putting anodes on keel and if so how has it gone?  If so, how were they attached to the keel and was it before or after the epoxy and antifoul were applied?  Also, how did you handle access to bottom of keel?

Thanks,

Bob

[altertraum]

I discussed the rust-on-keel-issue with an expert for antifouling and anticorrosion today. He is selling the stuff for underwater protection in Germany since decades (antifouling shop). His statement: The steel of all Bavaria and Beneteau keels is of a very poor quality. There are definitly patches of "strange" material included, which attract humidity, no matter if you have epoxy or other stuff between the steel and the water. He recommended to use a Chlorkautschuk-Primer on the rust patches and to apply antifouling on it. He also said, you have to renew that every three years, and if there is some unevenness: just ignore that and sleep well. I will do so. So for me: no sanding, no epoxy.

[JEN-et-ROSS]

"if there is some unevenness: just ignore that and sleep well. I will do so. So for me: no sanding, no epoxy".

  That, altertraum, is by far the most sensible advice I've heard in years, advice that I too will take.. ...Thanks for passing it on.

[altertraum]

Yes, sometimes life can be easy ... happy to share that

[Kibo]

Hi Kibo

Did you end up putting anodes on keel and if so how has it gone?  If so, how were they attached to the keel and was it before or after the epoxy and antifoul were applied?  Also, how did you handle access to bottom of keel?

Thanks,

Bob

Hi Bob,

Yes I fitted anodes to my keel. I had threaded bolts welded to either side of the keel so standard anodes can be fastened on with nuts. I had the keel totally refinished, sanded/grinding, primer and epoxy then antifoul. Last fit was electrodes, obviously not painted. Access to under the keel was achieved by using the travel lift over a weekend when the yard I was in does not launch or haul so once hanging access to under the keel was easy. After 6 months in the water no keel rust and some but minimal anode wear. They will last another season and probably more.

[Kibo]

Here photos of my project if interested.

Before, Epoxy primer, after with anodes (one either side)