Lead ballast in steel keel and salt water

[matan]

I suspect that there is salt water in the keel. The yacht is steel and the inside of the keel was well painted before lead was put in. The top was sealed with waterproof cement and an acrylic layer was sealed over the concrete. Saly ater is frequently on top of the cement. I am worried that there may be salt water and lead inside the keel. Would this have a bad effect?

[RaymondR]

Nothing will effect the lead but the steel will corrode. Do you know how the lead was fixed in place and whether it was cast blocks or shot.

[Pelagic]

Did you do the lead ballast installation yourself or are you relying on what you were told?

If unsure. You can do a week long test with fresh water, during a hot dry period as long as you can keep your bildge dry from other sources.

1. Measure the amount of fresh water it takes to level off at a high mark above the cemented ballast

2...in a week see how much has leeched under the cement by refilling to same mark.

If a significant amount then you gave a potential rusting issue down the road.

One solution when Drydocked is to drill tiny drainage holes in bottom (use hammer to hear void spaces) and let the water drain out. Hopefully not to Rusty but if so
.
Temorary plug holes then pour Turco rust convertor on top to drain down into void spaces to stop any further oxidization.

Drain again then pour a light oil like liniseed oil on top to drain into ballast area for a final flush.
Then burn rod into drill holes to seal off '

Keep poring oil on top to refill cavities.
then try and improve on your top seal coating to keep future seawater from displacing the oil

[matan]

Raymond and Pelagic
The lead was in sheets and has been rammed into the void that was left for that purpose. It is the front 40% ofthe keel the back 60% was installed before i saw it. I think it is welded shut. Would lead inthe keel with salt water create a galvanic current that couldlift the paint below the water line.
If you drill the keel when the yacht is out of the water and water comes out how would you dry the remaining lead before filling the keel withoil. Since oil floats on water any water leaking in later could be below the lead.

[Pelagic]

I honestly don't know about the increased galvanic action of a mix of salt water, mild steel and lead. Perhaps a metallurgists can tell you.

But Rust can be an issue if seawater is sitting in an area and the coating was damaged when the lead was hammered into the void.

For iron to become iron oxide, (Rust)
three things are required:
iron, water and oxygen.
By draining the water, treating the area with Turco,
https://youtu.be/k002TCz8JcY
then filling with oil, you stop oxygen from getting to the steel.
Last step, would be to better seal that area so the oil is not displaced

Perhaps with a bitumastic coating
http://www.ultracote.net/Home/products/BM360

[RaymondR]

Lead is more noble than steel so the steel will corrode to protect the lead. Consequently you need remove any water and seal the keel. The best way to ensure no future problems to plate it over. One of the better ways to check for leaks is to pressurize the void with air and then spray the outside with soapy water and look for bubbles. Be very carefull not to put more than a couple of psi of pressure on the void.

[Strabo]

Be very carful about pouring oil into voids. Oil in the voids will make welding the hull a fire hazard. Drilling drain holes has a major drawback. To stop the galvanic action all moisture must be removed. At least moisture which is conductive, i.e. salt water. Ultrsound transducers are available for rent. With a grid pattern placed on the hull present thickness of plates can be recorded and compared to future tests. Tough issue to resolve.

[Crusty Joker]

Group, suggest that the potential difference should be measured between lead and the hull / ground of the steel vessel. If there is different potential you have isolation that will create a battery and cause corrosion / electrolysis. Use zinc bolted solidly to steel. Connect lead to your bonding system if there is isolation so that potential difference is zero. You may also isolate zinc with an insulated plate and run to the zinc through a potentiometer to control voltage and current to protect hull and all things connected to the bonding system and slow sacrifice of your zinc. With a meter in this circuit you can monitor performance on a daily basis. It is important that wires of the bonding system be inspected and potential checked to be sure that there is electrical continuity. Rudder shaft, prop shaft, etc all need to be bonded to ground. Use shaft wipers with good spring load bronze and a split bronze bearing. Good luck with your project. Please post details if you notice any significant changes or observe corrosion / electrolysis. All metal goes to grounded bonding system. This goes to zinc. One zinc better than many in different places as long as bonding system is complete. This from Robert Shorey and Torrey Bartel.

[jakkum]

yes, lead and iron or steel in dalt water is a battery and the iron will corrode.
I think step one should be a thorough ulyradonic check for keelplate thickness.
To thin in places? Cut oyt and repair.
The good thing is that stap 2 is a lot easier: dry the inside of the keel and nake sure that no salt is left.

I the plates are still tbi k enough, find a eay to flush out the salt water and dry the inside.
Step three is to make sure that no salt eater can get back in
If possible, weld a top over the keel
I that is not posdible, you can fill the voids with an epixy, a solidifying bitumen or perhaps even a thin concrete.
If the top is on fact sort of airtight a bit, a vacuumpump can help yo get yhe stuff you eant to put in EVERYWHERE so there is nopmace for saly water anyeay

[t588143]

Corrosion needs a constant supply of significant amounts of oxygen which is not the case in your keel. Galvanic corrosion needs a constant supply of fresh solute( seawater) and a constant drain of saturated solute. Furthermore a significant potential differential is required, for steel this is - 0,43 volts and for lead -0,13 volts. This differential is not sufficient to cause any destructive galvanic corrosion. So do not drain any liquid which is already saturated but concentrate on casting the best possible seal.

[a64pilot]

Originally Posted by t588143

Corrosion needs a constant supply of significant amounts of oxygen which is not the case in your keel. Galvanic corrosion needs a constant supply of fresh solute( seawater) and a constant drain of saturated solute. Furthermore a significant potential differential is required, for steel this is - 0,43 volts and for lead -0,13 volts. This differential is not sufficient to cause any destructive galvanic corrosion. So do not drain any liquid which is already saturated but concentrate on casting the best possible seal.

Interesting to me was discovering that you could take a 55 gl drum and fill it with water and seal it by putting the top on or screwing on the caps.
A tiny bit of rust will form, but then all the O2 in the water will be consumed and the barrel will never rust from the inside, it will only rust from the outside in, even after decades the inside will still be pristine as long as there isn’t any O2 introduced.

[Pelagic]

Originally Posted by t588143

Corrosion needs a constant supply of significant amounts of oxygen which is not the case in your keel. Galvanic corrosion needs a constant supply of fresh solute( seawater) and a constant drain of saturated solute. Furthermore a significant potential differential is required, for steel this is - 0,43 volts and for lead -0,13 volts. This differential is not sufficient to cause any destructive galvanic corrosion. So do not drain any liquid which is already saturated but concentrate on casting the best possible seal.

That is great if there is no risk of galvanic corrosion.
But one question,
If that keel section is already saturated with sea water and as the OP stated, it is common for sea water to lay there....
..Why worry about trying to seal better?

[Pelagic]

Originally Posted by Strabo

Be very carful about pouring oil into voids. Oil in the voids will make welding the hull a fire hazard.

Yes, you should weld up the drain holes before saturating void spaces with oil as I clarified in my 2nd post.

I am not worried about putting oil in void spaces on a steel hull. It is a common practice to prevent corrosion.

My own Dutch steel boat was originally Skin Cooled ie long box sections about 3" deep from midships to aft cabin were built on either side of keel.
Engine and generator fresh cooling water was circulated thru there and the heat dissipated via the outside hulls contact with cool seawater.

At some point engine and gen were upsized and they switched to salt water cooling with heat exchangers.

Those void spaces were filled with diesel oil to stop internal corrosion as is my large rudder


On my first drydocking I opened and drained the diesel oil to check for corrosion. Absolutely zero. So I pumped back in the same old diesel (about 200 gallons) till topped up at header pipes, then sealed.

Obviously if you were doing any serious plate welding it would need to be gas free.
But in the OPs situation that is not the case.