LOVING YOUR BOAT TO DEATH – Electro-chemical Destruction / Underwater Rot

LOVING YOUR BOAT TO DEATH – Electro-chemical Destruction / Underwater Rot

The subject of electrochemical destruction and wooden boats has been covered extensively on WW – in fact the Chris McMullen articles are the most referenced stories on the site. At the end of todays story I have listed links to these stories.

Today thanks to Chris McMullen and Baden Pascoe we get to share an article they penned for the 2023 Mahurangi Cruising Club Year Book*, this article succinctly backgrounds the topic and suggests what as a wooden boat owner you should be looking out for and what to do to protect your wooden boat. READ IT. But if you are lazy – let me spell stout for you – DO NOT FIT ANODES or BOND YOUR WOODEN BOAT.

Note: PDF version below for easier viewing for the visually challenged – i.e. most of us 🙂

(*Article reproduction with the permission of the Mahurangi Cruising Club©️)






2 thoughts on “LOVING YOUR BOAT TO DEATH – Electro-chemical Destruction / Underwater Rot

  1. And still you see zinc appearing on wooden boats. What does it take to get the message across?
    Also need to remove all bonding wires if still lurking in the bilge.


  2. My old boat Northern Star currently has no anodes fitted, I was given one by the previous owner and told I needed to fit it, it appears to have had a couple in the past, the remains of either a strap on one side or the brass screws still fitted into the keel on the other. Philip Carey surveyed the old boat a year or two ago, sadly as a part of a deceased estate sale and noted significant green build-up on copper through hull fittings and his comments to me since were that this was a sign of fittings acting as a battery due to anodes being fitted and creating an electrical current with the salt-water, effectively creating a batteyr situation. He advised no anodes are need to be used on Northern Star, she has copper fittings and to do so would create an electrical current that would cause the aluminium portion so the fittings to erode, (I may not exactly recall this) that would eventually cause the fittings exposed to the salt water to weaken and fail… this makes sence, I look at the same fittings now he photographed and provided to me that were covered in a large green build-up and today they are nowhere near as bad in fact negligable after no anodes have been fitted for possibly a couple of years…whether that means anything or not, I don’t know.
    What I do know is the recent insurance inspection report that involved an out of water inspection by Phillip using a hammer and chisel/sharp-knife, inside and out of the boat all fo the timbers rang like a bell after 56 years….of hard-service, quite reassuring, I am following the advice of no anodes unless I can be convinicingly pursuaded otherwise.
    While recently out of the water I needed to replace a through-hull fitting the out-flow valve for the head,..the original bronze, through-hull fitting had at some time a mild steel sleeve screwed onto it and ontop of this a 316 stainless-steel valve. It literally broke of in my hand. (Lucky this did not happen on it’s mooring) The mild-steel was so rotten I could literally pull it apart using my fingers in places. I needed to cut-out the original through-hull fitting and remove this to replace it and this was as sound as it had been when it was originally fitted 50 odd years ago although I needed to destroy it getting it out because of the nasty mild-steel that had welded itself onto the fitting, It was interesting, three different metals and the mild steel had effectively destroyed itself first.
    I had a 32 foot Hartley built in 1978 before this and the white build-up shown in the photographs was evident on the top of the rudder shaft and oozing through the packing…this was quite significant, I also had significant green growth on through hull fittings…without knowing any of this I replaced a shaft anode and a large hull anode and added another anode to the rudder that was steel and had a stainless steel extension added to it at some time…..(that was probably the issue, disimilar metals rather than insufficient anodes) the white build-up continued unabated…..I might forward this article to the new owner,
    Like many unknowing boat owners we hear wooden hulls need anodes to stop electrolysis to timbers, expecially in marinas where each boat anodes-up and the problem of electrolysis passes along to the next boats in line….


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