electrolysis in wood

Anyone have any good reference links? Considering a wood boat, iron fastened, but is showing "signs of electrolysis" in some fastenings through the stem. The boat is on another continent, so I want to educate myself before going any further. Can it be local only?

 

Electrolisis causes a chemical reaction resulting in a mild acid. That is what deteriorates the wood. However, iron fastened hulls (it must be really old) also have damage from scale or pack rust. The oxidation expands the fasteners. Your best bet is to find a surveyor with knowledge of old wooden boats.

 

Yar, I had to cut out some damaged mahogany where some anode studs went through, but it was only local damage. Im familiar with rust expansion with iron, especially in oak. The owner is not entirely clued up, did not have a survey before he purchased or since. He says its electrolysis, but it could just be iron in oak reaction. 55 year old boat. He says it only local to one fitting, fine if accurate, but i have seen an entire below the waterline planking fastners being mostly pink powder. One is worth taking on, the other not so much.
I tried last year to organize a boat lift and survey but the 3 individuals involved could not make a date that worked.

 

Where is the boat?

 

San Francisco, California. Boatyards dont seem to want to touch anything anything wood, I got turned down even for temporary berthing, and thats by those who could be bothered to respond to email. Any good DIY yards on the Bay?

 

I am not familiar with that area. Marinas have had too many bad experiences with old wooden boats sinking and then abandoned.

 

Spaulding is a wood only yard in Sausalito.
Svens in Alameda has a competent wood write. The owner used to race a vintage wooden sloop.
Berkeley is an awesome diy yard.

Try contacting the Master Mariner's Society or the Wood Boat Racing Association.

 

They used to call it "Iron sickness" or "Nail sickness".
The Tannin in the Oak forms Tannic acid, fresh water is worse, no salt to fight against the acid.
Also, the term "Electrolysis" is not correct. Electrolysis is what happens when DC polarity is
intentionally reversed.
It's widely used for removing rust from parts, the parts being immersed in water with a little soda added.
The part to have the rust removed is hooked-up to negative, the sacrificial anode being positive.
In boats we're more concerned with stray current and/or galvanic action.
I'd be wary of any "surveyor" or boat inspector who uses the term "electrolysis", regarding boats.

 

For boats of a particular age and type, iron sickness is common. Wooden work boats were not built to last forever, just be economically viable in construction and operation. Then drive it up on the beach and burn it....
Try this reference and the Wooden Boat forum.
Wood: a Manual for Its Use as a Shipbuilding Material https://www.google.com/books/edition/Wood_a_Manual_for_Its_Use_as_a_Shipbuild/4LosAQAAMAAJ?hl=en&gbpv=1&dq=inauthor:%22United+States.+Navy+Department.+Bureau+of+Ships%22&printsec=frontcover
https://forum.woodenboat.com/forum/building-repair/1214-iron-sickness-pics

EDIT: xpost with rangebowdrie

 

Electrolysis, process by which electric current is passed through a substance to effect a chemical change. In boats with zinc anodes and iron fasteners a battery is formed which will generate electrolysis. The same will happen on a fiberglass boat with zinc and stainless. However, fiberglass is not affected by weak acids. Electrolysis is not a result of reversing DC polarity. It is the process that breaks water into oxygen and hydrogen. All acids contain hydrogen.

 

No, the Zinc anode/iron fastener issue is one of an "integral" current being formed, it is rightly forming its own battery, NOT electrolysis.
Electrolysis is dependent upon an OUTSIDE current being impressed upon the material(s).
And when we see the white punky wood around a bonded seacock, that is also NOT electrolysis, it's Hydrolysis.
A longtime friend of mine wrote the corrosion syllabus for the School of Wooden Boats.
He is also a court recognized expert witness in lawsuits that deal with boat/ship corrosion and has testified in several cases.
He also taught corrosion classes at the Coast Guard Academy and traveled around the US giving the ABYC classes and exams, you could say that he is the teacher of the teachers.
As an aside he is also a court certified expert witness on what's called "Electro-shock-drowning, ESD".
Yes, for years the word "electrolysis" has been bandied about by all kinds of writers and "so called" knowledgeable people but it is not correct.
IIRC, you won't find any part of the ABYC material on electrical/corrosion issues that uses that term as a definition for any forms of corrosion.

 

It is all about 'dissimilar metals' and whether there is means for an 'electrolyte' to occur - the flow of electrons between the 2 surfaces via a media that can carry the electrons from one surface to another.

More technically:- any corrosion reaction in aqueous solution (electrolyte) must involve oxidation (anodic reaction) of the metal and reduction (cathodic reaction) of a specimen in solution, with consequent flow of electrons between the two items that are reacting. Thus having dissimilar metals in a solution, electrolyte - seawater - creates a cell. The amount of eletrcial potential between the dissimilar metals governs the rate and amount of reaction and hence the amount of corrosion that occurs.

If the dissimilar metals are fully isolated, i.e. no path for the flow of electrons between the 2 metals, the only reaction/corrosion, will be the slow effects on the metal itself, in the seawater.

There is also of course the possibility (depending upon the metals) for erosion to occur as well.

 

I have no idea what "integral current" means. None of my electrical or electronic courses ever covered that. Could you please explain?
What do you mean by "forming its own battery"? A chemical battery is formed by two parts at different levels of the electrolytic scale. Electrolysis is the separation of oxygen and hydrogen from water. There is a redox reduction.

 

Granted, perhaps a poor choice of words to describe an action.
I said after that, "forming its own battery".
Maybe it would be plainer to say; "A situation which creates its own potential as opposed to one in which electricity is introduced from the outside".
A zinc connected to a bronze seacock by a bonding wire, vs. the same set-up that has the bonding wire "hot" from some source, as the neg on the batteries are generally connected to the engine/shaft/zinc on shaft.
We see similar issues when current leaks from bad connections on a bilge pump switch that's sitting in water that's around the keel bolts.

 

Thanks for the info Blueknarr.
Thanks all, maybe "hydrolysis" is a more accurate word, the majority of books on my shelfs regard metal wasting of 2 dis-similar metals on the scale as electrolysis. Waiting to hear back from a "marine surveyor", on his wood boat experience, before going further. What photos I had did not show any zincs on the hull, so I am wary that all the fastenings below the waterline may be effected, but that usually leads to blown bungs, weeping rust and distorted planks, which is not readily apparent.
On another note, i hear that teredo worm are common in the Bay area, so a haul out inspection for that also would be wise.