Electro-Chemical Damage In Wooden Boats Update

rudder electrochemical damage

A Special Post By Chris McMullen

Recently I received a note from Chris where he questioned if the story we posted last year on ww about electro-chemical damage to wood  was a little too long & were people reading it. Well I can tell you that the post is the single most visited story on ww, ever, & gets read by people all over the world. Its frequently referred to on the hugely popular WoodenBoat Forum in the USA. The link below takes you to the original story.


For the impatient ones out there 🙂 Chris has done a ‘Readers Digest’ version & refers to a vessel that recently featured on ww.
I encourage all of you to read today’s story & if you own a classic wooden boat – read both versions – the problem is the biggest risk to the life of our classic boats.

In Chris’s words:
“I received the above disturbing images of another woody being destroyed by an owner who I believe is unintentionally loving his boat to death.

The use of anodes and bonding on a wooden boat is fatal. The cathode or protected metal makes hydrogen gas and this combined with saltwater makes Sodium Hydroxide (Caustic Soda). This chemical is used to pulp wood in the paper making industry. Not on my boat thank you! I say again, there is no reason to use anodes and bonding on any boat. The only exception, steel hulls require anodes. If copper or bronze are being corroded it is due to a positive DC leak and Zinc anodes will not help. Find the electrical leak is the cure. If there is brass or manganese bronze underwater it will corrode due to the
zinc in the alloy. Anodes will possibly stop the corrosion but at the expense of wood damage. A better plan is to replace the brass with proper marine bronze.

Bronze and copper should last indefinitely in the sea. To prove that statement, I ask you to look at the Roman coins and artifacts salvaged from ships wrecked in the fourteenth century. There was no anodic protection and the metal is well preserved. So what is the difference to the copper and bronze on your boat? There is absolutely no difference so why waste your money buying anodes that will in time destroy
your wooden boat.

Three or four bottles of wine will cost the same as anodes and will make you and your boat happier.”

Note: ww is read all around the world, if there is water & boats, there are people reading ww. So a little about the man for non kiwi’s  – Chris is one of NZ’s most respected boat builders (retired) and at one time was the Lloyds (Honorary) Wood Boat Surveyor in Auckland. Chris’s (the original company) ‘McMullen & Wing’ built and repaired wood, steel and marine aluminium vessels. They built the first welded aluminum vessels in NZ. Chris is the current holder of the Classic Yacht Association of New Zealand ‘Outstanding Achievement Trophy’ for services to classic boating.

14-05-2016 Photo Update
Gavin Gault sent in the below photos of a Nova skeg floor that he believes were probably damaged due to engine – anode bonding failure. Pretty graphic !!

10-07-2016 Reply from Chris McMullen

“Wow. Thank you Gavin Gault for sharing your very graphic images. Very sad, small consolation but yours will not be the only wooden boat affected by this scourge.
Maybe, at last some of the Flat Earth Society will start to believe what I have been saying. The worst detractors are some in the Marine Industry who have been preaching the Anode, Bonding party line for years.  Now there is no where to run for cover,  they continue to conjure up excuses and it seems, refuse to accept a simple scientific fact.
“If you have a positive and negative electrode in salt water, the negative cathode or protected metal makes hydrogen gas and this combined with salt water makes Sodium hydroxide.”
This chemical is also known as caustic soda and removes paint and destroys wood.  There is no doubt about this fact. You do require a power source and bonded dissimilar metals ( zinc and copper) provide sufficient current to do the damage, but slowly.
If there is a negative DC leak (to the sea)on a bonded boat the process is accelerated. If there is a positive leak any metal becomes an anode and will waste away. It is important to isolate the DC power from contact with the sea. Again bonding is just asking for trouble. Please remove Anodes and Bonding from your wooden boat now!
Chris McMullen”

06-09-2106 In case you were not to sure what to look out for – the below photo should be a wake-up call to a few woodys 😉



13 thoughts on “Electro-Chemical Damage In Wooden Boats Update

  1. Pingback: What Does Electrochemical Deterioration In a Wooden Boat Look Like | waitematawoodys.com #1 for classic wooden boat stories, info, advice & news

  2. Our boat is Orion, a kauri trawler 52 ft 30 tons built by Harold Saunders in Paremata in 1962. We acquired her in 2015. After reading Chris’s article I have progressively reduced the number of anodes. This year we’re down to no anodes and no bonding. The electrical activity around the stern gland used to produce a cluster of crystals that I would wash away every weekend. Now it seems to be about every three months that there’s a hint of them, and I wash them away with kettle water and then coat the area with lanolin grease. I’d strongly endorse Chris’s view that anodes and bonding should be removed from kauri launches, based on our own experience.


  3. Pingback: Want to see what electrolysis does to a wooden boat? | waitematawoodys.com #1 for classic wooden boat stories, info, advice & news

  4. Hi Owen, It was me who took the photos. You were sealing the bottom of the boat as I took them and as you were going like hell, I did not bother you. If you remember I asked you the question” do you know what is causing this wood decay”, your answer was “no”. Then I went on to say, “are you a CYA member and do you follow Waitamata Woodys”? I think you said yes to both and then I recommend you read Chris McMullen’s well researched and proven articles on electro chemical destruction of wood.Then I left. I was going to call back but I have been out of the country for two weeks. . Please take this advice as constructive. I love your boat as it was built for Wren Carey, father of Roger Carey. The Carey family are personal friends of mine, in fact my son is named after Roger, a man I deeply respect.
    This issue can be rectified on your next slipping . Only too happy to help.


  5. To Alan and Chris,

    I unreservedly apologise for my comments. They were unfair and wrong.

    This article came as a complete shock to us after literally hundreds of backbreaking man hours over the last 3 weeks, performed by some very hard working and talented people who have put in huge days helping with all the maintenance we thought was required.

    I do wish you had contacted us while we were slipped as it would have made rectification a hell of a lot easier and it is disappointing the article begins by criticising our boat (and the owner) when we have only just purchased her and have already invested a enormous effort trying to preserve and do the right thing by her.

    My comments were still inappropriate and wrong though and again I apologise to yourself and Chris and the photographer.

    I wish you all the very best.


    Alan H Reply – thank you Owen. All good at this end & with CMcM. What size T-shirt are you, I’ll send you a ww shirt


  6. Good morning Owen
    I write in reply to your comments above.
    Firstly – the classic wooden boat community in New Zealand is full of passionate people who mostly have one core desire & thats the preservation & celebration of our maritime heritage. The waitematawoodys weblog was launched to provide a meeting point for these people. Somewhere to capture the growing interest in old wooden boats and to encourage and bring together people passionate about their preservation. From day one ww has always encouraged the exchange of knowledge about the care and restoration of these old vessels. Its for that reason that ww publishes articles like the one you have objected to.

    Owen – you have been very quick to criticize the writer of the article, myself & waitematawoodys – normally I would not waste the time replying but the writer is a friend & does not deserve to have your comments go un-answered.

    I have summarized below what I know about the photos.

    In early April you were hauled out at the Pier 21 slip, during this time numerous woodys sent me photos – some of which I published on ww. A passionate & very knowledgeable woody sent me the close-up photos of the rudder/keel area. He told me he spoke to someone working on the boat at the time & there was no interest in a conversation. I chose not to publish those photos. I understand that this woody emailed the photos to the ww article writer as evidence of whats happening to some of your vessels.
    At the same time (11-04-2016) I received the email below from a gentleman working on your boat
    11-04-2016 “Currently doing some work on xxxxxxx at the moment and thought I would share some pics now the hull has been stripped back showing the planks in fantastic condition. She’s so well made and still in great nick. Great to work on ones like this.”

    I replied
    ” Hi X, Thanks for these photos, yes she looks very smart. Interesting that I was sent some photos of xxxxxxxx by another ww follower last week, concerned that these was a lot of corrosion to the metal fittings. Have you noticed any?”

    I received on 12/04 the reply below
    “Hi Alan – Have not really noticed any corrosion on any metal. Bit of calcify de lignification around the prop stern tube but all pretty normal considering age. Getting rid of a few surplus metal fittings under the waterline as well. X”

    So Owen after reading the above & re-reading your comments above, I think most people would agree that all the people you are taking a pot-shot at are to use that great saying ‘standing on thick ice’ – I think it might be time to take a big bite of the old humble pie……………… what say you?

    p.s. I would suspect the the writer did not even know the name of you boat, they were just using the photos to support the story. A story that is trying to enlighten people on how they can preserve our classic wooden fleet.


  7. One would have to question the motives of the people who put together this article. Is it to assist and aid the preservation of classic wooden boats?

    In Chris’s words:
    “I received the above disturbing images of another woody being destroyed by an owner who I believe is unintentionally loving his boat to death.”

    Nasty and malicious words towards us and our boat – yet why? Whoever was crawling around under the hull to take the pictures didn’t even have the common courtesy to speak to us about this issue. We would have been only too happy to attend to anything that needed rectification to preserve our boat had anyone bothered to let us know. Not only did the authors and collaborators of this article say absolutely nothing, they waited 3 weeks until we were back in the water before publishing this – making any remedy extremely expensive and complex, when it could have been dealt with right then.

    We have not owned the boat 3 months. We have never owned anything like this before and are completely dependant on the advice and expertise of others. Instead of assisting us to do what is required to look after our beautiful vessel, people have collaborated to criticise and malign when they could have chosen to help and demonstrate the correct maintenance procedure instead. Where is the love of wooden boats in that?


  8. An informative article. Peerless needs major surgery to keel, hog and some floors for this reason. I will be considering an eventual return to a bronze prop shaft to reduce the need for zinc, and various other bits of steel have been added over the last century (steel rudder and sternpost and steel coach bolts in the stem). The sad thing is that some people are still providing paid professional advice to owners advocating more zinc on their copper, bronze and wood-constructed classics.


  9. The pohutukawa stern knee on Waitere II (H2, 1913) had been in place at least since 1972 when I acquired her. Suddenly last year she was blasted into splinters, wood-dust and white crystals extending out from the keel-bolt that tied her in. (I would include photos if I knew how to do it).

    I have always had a zinc on her propeller shaft housing, but had only the year before bonded this to the rudder pintle as well. I had also suspended overboard another zinc attached in the bilge to a strap on her new stainless steel drive shaft.

    George and Pam Emtage of Whangateau Traditional Boatyard had informed me regarding McMullen’s and Alan’s warnings. George replaced the knee with wonderful work, and found no further sign of wood or keelbolt deterioration in the prop log or stern centrepost beneath it. He left it to me whether or not to disconnect the new bonding. I decided to keep it all as it had been for the last year, but also keep a close eye on that keelbolt and all other troublespots… and hope for the best.

    Thanks for your support,
    Steven Webster, Ponsonby.


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