Discolored hull paint, bonded thru hulls with no anode

[Bowdrie]

Originally Posted by boatpoker

As a retired Certified Marine Corrosion tech I don't agree (completely) with a single post on this thread.

I'm quite sure that any of us who've posted on, (or even been reading,) this thread could say the same thing.

[boatpoker]

Originally Posted by Bowdrie

I'm quite sure that any of us who've posted on, (or even been reading,) this thread could say the same thing.

At least no one (yet) has claimed it was 'electrolysis'

[Bowdrie]

Originally Posted by boatpoker

At least no one (yet) has claimed it was 'electrolysis'

We'll probably have to get into this thread for a few more pages before that word pops up.

Anyway, just to throw out some stuff.
We all know that the Tiawan boats of that era generally had problems with their "stainless" steel.
The same, (to a lesser degree,) also with "Bronze".
As Tiawan was a big player in the shipbreaking business, all the copper-based alloys from the ships got "thrown into the pot" to be melted down and made into deck fittings/steering gear parts/portlights/seacocks/thru hulls/cabinet hardware, and a myriad of other things.
This basically led to next to nothing being produced from a "Certifiable alloy".
Then in many cases all the "mixed metals" were connected-up with non-tinned wire, (frequently with fittings and orientation which would allow water ingress into the wire strands,) and including the steel/stainless steel/aluminum tanks into a bonding scheme.
Playing "fast and loose" with the ships wiring never helped either.
Now, we add that into stainless keel bolts, (usually having bilge water around them,) going into an iron keel, and an engine connected electrically to the prop shaft/prop.
Electricity does not take the path of least resistance; its flow takes all available paths in its quest to get back to its source, the flow being proportional to the resistance of each path, (resisters in parallel).
Taken as a whole, it's a wonder that there aren't more problems.

[boatpoker]

Originally Posted by Bowdrie

We'll probably have to get into this thread for a few more pages before that word pops up.

Anyway, just to throw out some stuff.
We all know that the Tiawan boats of that era generally had problems with their "stainless" steel.
The same, (to a lesser degree,) also with "Bronze".
As Tiawan was a big player in the shipbreaking business, all the copper-based alloys from the ships got "thrown into the pot" to be melted down and made into deck fittings/steering gear parts/portlights/seacocks/thru hulls/cabinet hardware, and a myriad of other things.
This basically led to next to nothing being produced from a "Certifiable alloy".
Then in many cases all the "mixed metals" were connected-up with non-tinned wire, (frequently with fittings and orientation which would allow water ingress into the wire strands,) and including the steel/stainless steel/aluminum tanks into a bonding scheme.
Playing "fast and loose" with the ships wiring never helped either.
Now, we add that into stainless keel bolts, (usually having bilge water around them,) going into an iron keel, and an engine connected electrically to the prop shaft/prop.
Electricity does not take the path of least resistance; its flow takes all available paths in its quest to get back to its source, the flow being proportional to the resistance of each path, (resisters in parallel).
Taken as a whole, it's a wonder that there aren't more problems.

I don't believe thats ..... oh... wait a minute, I agree with every word

[LifesBetterWhenYoureBeating]

Originally Posted by goboatingnow

Definitely try and keep ac and Dc ground separate , if worried with a whole boat RCD as additional AC protection

The simpler way seems to be to replace the main breaker on my AC panel with an ELCI one? Is that good enough?

[goboatingnow]

Originally Posted by LifesBetterWhenYoureBeating

The simpler way seems to be to replace the main breaker on my AC panel with an ELCI one? Is that good enough?

RCDs are great use them everywhere. At least one in the AC panel 30 mA trip

[mitiempo]

Originally Posted by LifesBetterWhenYoureBeating

The simpler way seems to be to replace the main breaker on my AC panel with an ELCI one? Is that good enough?

An ELCI is there for safety. It has nothing to do with corrosion protection.

The choices for corrosion protection from other vessels on the same circuit are a galvanic isolator (good) or an isolation transformer (best).
Neither of these items will protect your underwater metal from problems on your own boat.

[goboatingnow]

Originally Posted by mitiempo

An ELCI is there for safety. It has nothing to do with corrosion protection.



The choices for corrosion protection from other vessels on the same circuit are a galvanic isolator (good) or an isolation transformer (best).

Neither of these items will protect your underwater metal from problems on your own boat.

Well yes and no. You can take the view that a RCD allows you to degrade direct connections to seawater as the RCD aids safety. Disconnecting sea water to earth wires connection with more RCD projection does improve corrosion resistance.

May not be “ code” of course but it’s the thinking person response

[mitiempo]

Originally Posted by goboatingnow

Well yes and no. You can take the view that a RCD allows you to degrade direct connections to seawater as the RCD aids safety. Disconnecting sea water to earth wires connection with more RCD projection does improve corrosion resistance.

May not be “ code” of course but it’s the thinking person response

True, if ABYC isn't followed.

Unlike the EU, ABYC requires the AC ground to DC negative connection with or without an ELCI (RCD).

[nofacey]

No anode is your main issue - bad for all underwater metal. Buy 2, keep one on hand

[goboatingnow]

Originally Posted by mitiempo

True, if ABYC isn't followed.



Unlike the EU, ABYC requires the AC ground to DC negative connection with or without an ELCI (RCD).

Oh I know but realistically ABYC has its head up it’s “ rear end” ( insert national slang here ) in relation to this. It’s entirely focused on swimmer electro shock issues when realistically this is a NEC supply protection. Issue.

[s/v Jedi]

The best thing that you can do is disconnect all wires from those thru-hull fittings.

The second best thing is to have a professional review your boat electrical system. It is not as easy as popping a different breaker in somewhere.

If you use shore power then make sure to at least have a galvanic isolator or better (like an isolation transformer). Do not leave the boat in a slip with shore power connected when you don’t have these.

[goboatingnow]

Originally Posted by s/v Jedi

The best thing that you can do is disconnect all wires from those thru-hull fittings.



The second best thing is to have a professional review your boat electrical system. It is not as easy as popping a different breaker in somewhere.



If you use shore power then make sure to at least have a galvanic isolator or better (like an isolation transformer). Do not leave the boat in a slip with shore power connected when you don’t have these.

Listen to father Nick

[LifesBetterWhenYoureBeating]

Originally Posted by s/v Jedi

The best thing that you can do is disconnect all wires from those thru-hull fittings.



The second best thing is to have a professional review your boat electrical system. It is not as easy as popping a different breaker in somewhere.



If you use shore power then make sure to at least have a galvanic isolator or better (like an isolation transformer). Do not leave the boat in a slip with shore power connected when you don’t have these.

I don't usually need shore power so this had been low on my todo list. I'm now going to leave the boat on a slip and so want to get this right.

All my underwater metals are now isolated.

My AC ground and DC negative are not connected

My DC negative is connected to my engine and that provides a path to earth via the prop shaft

As I understand it, this configuration will stop galvanic corrosion from current generated by other boats but won't provide safety against AC faults on my boat?

If I connect my AC ground to my DC negative and install a galvanic isolator, will that provide safety from AC faults with no risk of galvanic corrosion?

Sent from my SM-A225F using Cruisers Sailing Forum mobile app

[boatpoker]

Originally Posted by LifesBetterWhenYoureBeating

As I understand it, this configuration will stop galvanic corrosion from current generated by other boats but won't provide safety against AC faults on my boat? [/URL]

Altho' theoretically possible, after hundreds of corrosion surveys I have yet to see another vessel be the issue. I have always found the corroding boat to be the master of it's own disaster. It seems that owners prefer to blame someone else rather than look at their own boat.