ELECTRO-CHEMICAL DAMAGE IN WOODEN BOATS UPDATE
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!
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 😉
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I have a 50ft 1936 yacht she has no bonding as such, although there is a connection to Earth from the HF, from memory it goes to a a keel bolt. I have three anodes. One on the stainless prop shaft, one on stainless steel cheak plates on the timber rudder and one on a stainless component that supports the rear rudder bearing, should I get rid of the anodes?
FYI. This is the most visited story on WW.