I had someone ask me if my seacocks were grounded as I have a fitting connected to one of seacocks that has deteriorated. I checked and don't see any of my seacocks as being grounded (wire from each to a zinc anode). Was it done from the factory or has anyone grounded all their seacocks. Gentleman on my dock said it would help prevent corrosion.
Seacocks Grounded?
- Thread starter Dadawada
- Start date
Beneteau and other European builders don’t always bond seacocks at the factory. I know mine on a 2014 Beneteau are not bonded. The idea behind their decision is that since the fittings are not connected to anything else they aren’t subject to dissimilar metal or impressed current corrosion from any other source. The downside is that since they’re not connected to the sacrificial anodes there’s nothing to protect from dissimilar metal corrosion within the fitting itself. On Beneteaus this problem is compounded by the fact that Beneteau sometimes used seacocks made of a form of brass that’s not very corrosion resistant.
If it were me I’d probably not try to add a bonding system to the boat. I’d replace the deteriorated fitting, and probably all of the other seacocks, with proper bronze fittings. At a minimum I’d inspect all of the others for any pink metal that’s a sign of dezincification and brittleness.
If it were me I’d probably not try to add a bonding system to the boat. I’d replace the deteriorated fitting, and probably all of the other seacocks, with proper bronze fittings. At a minimum I’d inspect all of the others for any pink metal that’s a sign of dezincification and brittleness.
It's somewhat of a debated issue as to what is best. Many boats don't have bonded (grounded) thru-hulls from the factory. It adds complexity and cost at the factory and requires you to keep the electrical connections fresh. If your thru-hulls are bronze or Marelon, there isn't much reason to be overly concerned beyond your normal maintenance routine about your thru-hulls experiencing corrosion, even if they're not bonded (you wouldn't bond a Marelon thru-hull anyway since they're non-metallic).
If you look around the net you will probably find some info from Nigel Calder advocating for bonded thru-hulls due to safety concerns related to an AC fault to a thru-hull or other underwater metal. From what I've read, bonding the underwater metals together can spread the AC fault across many different metals rather than a single, very hot metal. I would say that this is more of a manufacturer level discussion than an individual owner discussion. As someone who has been shocked while diving a boat (in salt water but from a fault at the dock, not from the boat itself) I can understand this concern, but I wouldn't say that you should feel overly concerned about it.
There are other, good ways to minimize AC shock risk. Keep your boat's wiring in good condition, make sure you know what you're doing any time you deal with an electrical project (especially having to do with 120V AC), shut off your shore power and inverter (if applicable) when your diver comes to visit to service your boat, and don't swim at your marina.
If you look around the net you will probably find some info from Nigel Calder advocating for bonded thru-hulls due to safety concerns related to an AC fault to a thru-hull or other underwater metal. From what I've read, bonding the underwater metals together can spread the AC fault across many different metals rather than a single, very hot metal. I would say that this is more of a manufacturer level discussion than an individual owner discussion. As someone who has been shocked while diving a boat (in salt water but from a fault at the dock, not from the boat itself) I can understand this concern, but I wouldn't say that you should feel overly concerned about it.
There are other, good ways to minimize AC shock risk. Keep your boat's wiring in good condition, make sure you know what you're doing any time you deal with an electrical project (especially having to do with 120V AC), shut off your shore power and inverter (if applicable) when your diver comes to visit to service your boat, and don't swim at your marina.
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Bonding is not settled science. The issue is galvanic corrosion from dissimilar metals immersed in sea water near by. Basically the metals form a battery with one metal becoming the anode, the other cathode. In order for the galvanic action to occur the circuit between the two metals must be completed by connecting the two metals with a wire. The no bonding advocates argue that isolated metals, seacocks for example, are immune to galvanic action because the circuit is not completed.
The Bonding advocates argue by connecting all the in water metals the electrical potential between the metals is equalized and galvanic corrosion won't occur.
I fall mostly in the bonding is unnecessary camp.
The Bonding advocates argue by connecting all the in water metals the electrical potential between the metals is equalized and galvanic corrosion won't occur.
I fall mostly in the bonding is unnecessary camp.
All metal thruhulls immersed in the same ocean are inherently all at the same potential and are grounded and bonded.
Not exactly. If they are dissimilar metals in an electrolyte (sea water) they are basically a battery. Connect a volt meter to a chunk of zinc and a stainless rod in salt water and you’ll see a potential. As long as the two aren’t also connected by a wire it’s like having a battery sitting on a shelf - the parts just sit there at their relative potentials. When the two parts are bonded by a wire electrons can flow through the wire, deteriorating the less noble metal (like discharging a battery). To prevent that from deteriorating the metal you care about you add an even less noble metal to the circuit to sacrifice itself.
This is correct. It is the mechanism behind the galvanic potential charts you see floating around in different places:
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 24,753
If you want to know for sure, there is a tool you can get from:
boatzincs.com
It is a corrosion reference electrode. You can use it to see the potential of metals on your boat. Unsure if the zinc is working on your shaft? This tool can let you know.
Corrosion Reference Electrode with User's Guide | BoatZincs.com
Corrosion Reference Electrode with User's Guide | BoatZincs.com | America's Superstore for Marine Anodes
boatzincs.com
Correct. I should have said “all similar” thruhulls instead of assuming they are.