tiny bumps on lead keel

[Bowdrie]

Originally Posted by Fishspearit

So to reiterate: SV Jedi unorthodox wiring=more likely to suffer stray current corrosion
ABYC standards=designed to reduce the risk of stray current corrosion.

You are putting the cart in front of the horse, and Jedi is correct.
In the "Old Days", the "higher end" boats had bronze seacocks, bronze thru hulls, bronze rudder shafts, bronze prop shafts, bronze struts, bronze fasteners, bronze props, bronze keel bolts, and the tanks, (both water and fuel,) were of copper-based alloys and used copper plumbing.
And everything co-existed peacefully with no bonding and no zincs.
As time progressed the use of inferior, (cheaper,) metals became more common and corrosion issues began popping up.
The "answer" was to bond everything to a sacrificial zinc to save the cheap metal.
Of course, then issues with delignification of the wood started appearing.
But we can leave that alone for now, as it's not germane to the discussion.
When AC became common on boats people started getting shocked, the answer was to keep the bonding and connect the AC green/ground wire to the bonding to form a low resistance path to the water.
That method is to protect people, it does nothing to prevent galvanic or stray current corrosion.
In fact, it promotes corrosion should a fault occur.
Today, boats have a "witches' brew" of all kinds of dis-similar metals, some in contact with the water, some not.
When they're all connected together the stage is set, now we just need a few electrons to find a path, and they will, and loose electrons are pretty devious.
Fortunately, we now have devices/gizmos that provide safety for people and safety for the metals in and on the boat, as well as a swimmer in the water next to the boat.
There are "Impressed Cathodic" systems, but they too are subject matter for their own discussion.

[Don C L]

Originally Posted by PeterWright

If I scrape them, they will come off, but leave a pit in the epoxy.

So just to clarify, a lead keel with an epoxy barrier coat? And when you scrape off the blister you still see epoxy underneath or you see lead? I have pondered whether stray current may somehow affect osmotic blistering because I have heard folks say something similar to what you are showing, in both hulls and keels that had never had blistering before, but I don't know of any confirmed electrical/chemical mechanism for that. (I'd love to hear about it if anyone knows.) The lead is not susceptible to corrosion in any way I am aware of and in fact you are describing blisters in the epoxy, not the lead, right? I wouldn't be concerned about them in any case except if you are racing and want to squeeze out that .001 of a knot.

[s/v Jedi]

Originally Posted by Don C L

So just to clarify, a lead keel with an epoxy barrier coat? And when you scrape off the blister you still see epoxy underneath or you see lead? I have pondered whether stray current may somehow affect osmotic blistering because I have heard folks say something similar to what you are showing, in both hulls and keels that had never had blistering before, but I don't know of any confirmed electrical/chemical mechanism for that. The lead is not susceptible to corrosion in any way I am aware of and in fact you are describing blisters in the epoxy, not the lead, right? I wouldn't be concerned about them in any case except if you are racing and want to squeeze out that .001 of a knot.

Yes, I noticed that in the OP too. If there is epoxy inside the holes and there is no exposed lead, then this damage occurred earlier and was fixed using a putty that now fell off.

[Don C L]

I've also pondered whether barrier coats and bottom paints may have some as yet undescribed incompatibility that may play a role.

But then I ponder a lot of odd things.

[s/v Jedi]

Originally Posted by Don C L

I've also pondered whether barrier coats and bottom paints may have some as yet undescribed incompatibility that may play a role.

But then I ponder a lot of odd things.

Bottom paints loaded with metal are questionable so a barrier coat needs to go onto the lead. Those are okay though, you can consider them just an epoxy with magic stuff like mica flakes that are not conductive.