Keel "Deposits" - What are they?

[FoxyCal]

We pulled our Cal33 last week and found rounded lumps of material on the keel's port side. They pop/scrape off and crumble into white powder. Here are two photos. What is this stuff?

[Manateeman]

We’ve seen split rudder on a 33 but can’t remember the keel construction. Anything inside near the keel look cracked?
Is the outside of the keel laminated glass over or just lead.
Tap it. Any filler or solid lead. Did you grind any stuff to see what’s underneath the antifouling?
More photos after removing the paint please.

[FoxyCal]

Thanks for responding, Manateeman. The keel is external lead with barrier coat. I have had to sand and epoxy some areas from time to time when white crusty spots have appeared before but this is a new level of “stuff”.

[JPA Cate]

I haven't seen exudate from keels that looks like that. So, I don't know at all. When you haul out, sand that back, and see what you find.

Ann

[Manateeman]

Sometimes fillers mixed in with epoxy will expand off the lead ..but that’s rare and is usually where too much filler was used without fiberglass as a reinforcement. I’ve seen a lot of home made lead keels have pockets of slag but not in production boats. A keel bolt problem on ONE side? That’s the interesting thing. Why just one side has got us flummoxed.
OK. Lead and aluminum form a soft oxide and maybe that’s what you have. We are thinking water down the keel bolts ? Are the nuts on top and inside OK ?
Is the hull being supported well enough to see if the keel is loose? How long sitting. Usually in the lift it’s easy to see if the keel is not tight..leaks, shakes...
but if things look tight, I’d do a little light grinding and picking and find a old plumber who remembers lead caulk joints and ask if he thinks it’s slag from the lead. Photos inside of the keel bolts please.
The manatee crew.

[Tetepare]

It’s filler.

[JC Reefer]

It crumbles? Put some of the crumbled dust into a cup of white vinegar. If it bubbles then you have calcium and likely some hardy coral that was making a reef on your keel.

[FoxyCal]

Manateeman, the keel bolts are clean and tight. JC Reefer, the substance dissolves in vinegar (takes several hours) but does not bubble. Not a lot of coral in Long Island Sound off the CT coast but could be some related organism I suppose. Tetepare, no filler on the keel as far as I know.

Thanks all.

[JPA Cate]

You might ask around the boatyard and ask if anyone has seen that kind of exudate or growth. If it is some kind of marine growth, someone else will have seen it. The distribution looks weird to me to be from filler, but like I said, I haven't ever seen something like that. I'd be tempted to sand it off, and see what's under it, if anything.
Interesting that it dissolves in vinegar, but not definitive, as there might be fillers that would, though it seems unlikely.

Ann

[rslifkin]

I've gotten a very similar substance on my aluminum anodes in fresh water. Only the ones on the trim tabs though (they see the least water movement). Never figured out what it is though.

[Searles]

Have witnessed similar deposits on a lead keel cast in the late sixty’s ,the ultimate result was anti fouling primer undercoats of a modern formular interacting with the impurities in the original casting,plus the fact that an earth strap for the radar and hf plus the engine to a seperate zinc anode ,changed the anode to alu and cut the keel loose ,fixed ,this had been a problem for many years on this vsl .⛵️⚓️

[goboatingnow]

From practical sailor. It’s a form of corrosion often from the antifouling

“
However, it is common to see lead keels with crumbly, whitish surface deposits, which when scraped away reveal a porous surface where the lead has corroded. Fortunately, the surface of a lead keel does not corrode and pit in the same manner as an iron keel, and reasonable repairs can be made without expensive equipment.

A drill-powered wire brush will usually grind away surface deposits and do an adequate job of cleaning out shallow corroded areas. It is important to remove as much of the crumbly oxidized lead as possible, to create a good surface for filler bonding.»

[Manateeman]

Boat keels poured in the back yard would have all sorts of defects mostly due to the impurities in the lead being melted. The stuff that floated to the top was called slag but nobody got it all skimmed off.
I stated I didn’t think you would find this in commercial keels but as far as quality goes, your talking about keels not defects in mast extrusions.
So maybe it’s just oxidation. Casting defects. Impurities in the lead.
Why one side is still interesting. Was that side in the sun?
Anyway...nothing to panic over.
Mark