Is this electrolysis ?

[Superaquarama]

Never had much trouble with electrics on various boats but, owning a Boston Whaler for a couple of years, I'm finding them a bit of a nightmare. She sits on a mooring, with the outboard lifted clear of the water when at rest.

Corrosion on terminals and wires breaking off at connectors, a Holt fusebox literally falling apart, etc. I thought at first that it was poor quality stuff, and indeed it may be, but it's got me wondering.

Fairly simple setup - 12v battery, electrics to the outboard, vhf, Garmin gps/fishfinder, nav lights, auto bilge pump and a 5w solar panel to keep the battery topped up.

Should I fit a sacrificial anode and, if so, where ? GRP hull, of course. Or should I just try and find high quality wiring connectors etc. (if so, what?) and beef up everything ?

Thanks,

Anthony

 

[vyv_cox]

I don't see how your problems can be galvanic with no metal parts in the water. I suspect you are seeing general corrosion in a marine environment. I assume you disconnect the battery when leaving the boat, as this would prove the point. Protection would seem to be the answer: I use Waxoyl on carbon steel parts like engine mountings, easily applied from an aerosol and dries to a fairly durable skin.

 

[dje67]

ACF50 is good - I've used it on many electrical and engine bits and it works well.

 

[Superaquarama]

Thanks, guys.

Well, the outboard itself is tilted clear of the water but the transom mount part of it is, at the very least, awash. I leave the battery connected to operate the bilge pump, without which the boat would just fill with rainwater / spray.

Just Googled ACF 50 as I'd never heard of it, but both it and Waxoyl sound useful and I'll try some.

 

[theoldsalt]

....... I leave the battery connected to operate the bilge pump, without which the boat would just fill with rainwater / spray......

No reason why you cannot fit a battery isolator switch for all domestics/engine start but wire the auto bilge pump on the battery side of the isolator via the correct fuse so that is the only device that is "live" when you leave the boat - fairly common practice and far safer than leaving everything connected to batteries.
.

 

[Superaquarama]

Thanks, Old Salt - sounds an excellent idea - the pump is already wired direct to the battery, so should be simple.

 

[Greenheart]

Six months ago I needed to bulk-out the shackle on my mainsheet block. I knew two pennies each side was the right width, so with a magnet I selected old copper ones, not the rusty modern steel ones...but it hadn't occurred to me that copper would degrade, too...

...is this electrolysis?

 

[VicS]

Six months ago I needed to bulk-out the shackle on my mainsheet block. I knew two pennies each side was the right width, so with a magnet I selected old copper ones, not the rusty modern steel ones...but it hadn't occurred to me that copper would degrade, too...

...is this electrolysis?

No, not unless you have a battery connected to it and hidden from view.

Probably just corrosion in a salty atmosphere but presumably it is doused in sea water regularly so there may be some galvanic ( dissimilar metals and all that stuff) action taking place while it is wet

 

[Lon nan Gruagach]

Galvanic corrosion eats holes, so the green pennies are not suffering (might be something nearby that is though). For it to occur there must be a circuit, the same body of water must touch both metals and there must be another connection between the 2.

 

[bitbaltic]

No. It's just electron exchange between the copper metal and salt in seawater/salty environments allowing oxygen to bond to the metal and form copper oxide. Ie, it's oxidisation- just the same as rust on steel.

 

[VicS]

Galvanic corrosion eats holes, so the green pennies are not suffering (might be something nearby that is though). For it to occur there must be a circuit, the same body of water must touch both metals and there must be another connection between the 2.

I'd say the green deposit was the result of slight corrosion of the pennies. Similar to the verdigris, usually considered to be basic copper carbonate, formed by prolonged weathering of outdoor copper structures. In this case probably a basic copper chloride produced more quickly as a result of being sandwiched between slightly more cathodic stainless steel items and frequently wetted with seawater.


It is difficult to imagine what other items there might be nearby and electrically connected in a GRP dinghy that might be suffering

 

[Greenheart]

Umm...please forgive my deep thickness here gentlemen...but I don't understand where electrolysis ends and galvanism starts.

In truth, even if you explain, in the next six months I'll probably post another pic of two adjacent yet dissimilar metals aboard my boat, one gradually dissolving the other, and I'll ask again what is going on and what I can do to prevent it.

But regarding my greenish mainsheet-block coinage, given that the hardware is stainless steel and the coins are copper, can I relax knowing that I'm unlikely to do more than four pence' worth of damage, however long the reaction continues?

Jeepers Vic, you must have sent that reply about five seconds before I did!

 

[VicS]

Umm...please forgive me deep thickness here gentlemen...but I don't understand where electrolysis ends and galvanism starts.

The term "electrolysis" is usually reserved for when the process is driven by an external voltage source. Remember the Hoffman voltameter . No dissimilar metals involved.

Galvanic corrosion refers to the situation when the process is driven by the small emf that is produced by a pair of "dissimilar" metals immersed in seawater ( or other electrolyte perhaps)

It is an informal distinction though which you may not find defined in the text books

 

[Lon nan Gruagach]

Umm...please forgive me deep thickness here gentlemen...but I don't understand where electrolysis ends and galvanism starts.

In truth, even if you explain, in the next six months I'll probably post another pic pf two adjacent yet dissimilar metals aboard my boat, one gradually dissolving the other, and I'll ask again what is going on and what I can do to prevent it.

But regarding my greenish mainsheet-block coinage, given that the hardware is stainless steel and the coins are copper, can I relax knowing that I'm unlikely to do more than four pence' worth of damage, however long the reaction continues?

Jeepers Vic, you must have sent that reply about five seconds before I did!

Electrolysis is the immediate result of galvanism, and it is actually the electrolysis that does the damage.
In detail.
Galvanism is the term for an effect discovered by Luigi Galvano (might get back to him later). He was experimenting with dead frogs and electricity. He observed that if the frogs were strung on an iron wire (a happenstance at one of his demonstrations) and a copper wire touched both the iron wire and the innards of the frog then the effect was the same as if he had used his regular source of electricity.
Not sure how far he got with measuring it, but each metal will generate a different potential when immersed in a corrosive solution.

So, with different metals immersed in the same solution they will generate different voltages, if you connect these together a current will flow. Something that may happen then is electrolysis (it depends on the metal and solution). At the more negative terminal electrons will leave the metal and enter the solution (ionizing its molecules). At the positive terminal its positive charges that try to make the reverse journey, the problem is that a positive particle can only be an atom missing an electron or so. Its these positively charged atoms that are your boat.

So, electrolysis can be forced to happen by applying a current, or the current can come from galvanism.


Now, we have all heard of the Volt from Alessandro Volta. Galvani might have had the limelight save for his belief that there were 2 types of electricity, the man made static electricity and a divine or animal electricity that could not be made. In his frog experiment he thought that it was animal electricity escaping that caused the frogs to twitch. Note though that at the time the only link between natural electricity (lightening and electric eels) and man made stuff was that a shock from either felt the same. Yup, you got it, lightning === static as they feel the same.

 

[macd]

The term "electrolysis" is usually reserved for when the process is driven by an external voltage source. Remember the Hoffman voltameter . No dissimilar metals involved.

Galvanic corrosion refers to the situation when the process is driven by the small emf that is produced by a pair of "dissimilar" metals immersed in seawater ( or other electrolyte perhaps)

It is an informal distinction though which you may not find defined in the text books

I bet that at this very moment, Dan is slapping his forehead and saying to himself, "Hoffman voltameter, you dummo, how could you possibly have forgotten?"

Vic, I value your expertise hugely. But if you think that 'Hoffman voltameter' or 'emf' (or even 'text books' on this particular subject) mean anything to dancrane, then I respectfully suggest you invest in shares in cloud cuckoo land.

No disrespect meant to you, dancrane, or your intellect. And certainly none to Vic's either. But I didn't expect to see an exchange like that since Monty Python went off air. It rather reminds me of the Jean-Paul Sartre sketch. But then I did used to frequent a pub where Wittgenstein once lived...:ambivalence:

 

[VicS]

I bet that at this very moment, Dan is slapping his forehead and saying to himself, "Hoffman voltameter, you dummo, how could you possibly have forgotten?"

Vic, I value your expertise hugely. But if you think that 'Hoffman voltameter' or 'emf' (or even 'text books' on this particular subject) mean anything to dancrane, then I respectfully suggest you invest in shares in cloud cuckoo land.

No disrespect meant to you, dancrane, or your intellect. And certainly none to Vic's either. But I didn't expect to see an exchange like that since Monty Python went off air. It rather reminds me of the Jean-Paul Sartre sketch. But then I did used to frequent a pub where Wittgenstein once lived...:ambivalence:

If one bumbling old pensioner can remember a Hoffman from his school days I dont see why Dancrane should not also.

However thanks for the investment advice. I will get onto my broker in the morning. I hope you are qualified to give financial advice .

Perhaps the explanation from Dougal Tolan will be more appropriate and helpful. I guess it will be if Dan's dinghy is full of frogs. It could be. I did hear of family of eastern europeans camping under an upturned dinghy in one nearby boatyard

 

[William_H]

Back to the OP question. No I don't have an answer but can report a similar problem. I use a wet NiCad battery permanently connected to a small solar panel. The bolts of the pos terminal are plated brass I think the nut is plated copper. I fit an AMP lug (copper) under the nut of the pos terminal. Large hole small lug with 18g wire. So last night race turn on lights no lights. I find the terminal corroded off. I am a wake up to this problem now. Got by by stripping the wire bare and clamping under the nut. Now I have certainly replaced this lug connection every winter and if i remember rightly this lug was replaced 3 months before the last failure. Yes I coat all the terminals in vaseline or grease.
It only occurs on the positive terminal. I presume it is an electrolysis driven by the battery voltage in the humid salt laden air.
Obviously for me the answer is heavier wire and heavier lugs. It might then last a bit longer. olewill