Rust in steel Schooner bilge? Some say "run"?

[Standbly]

Epoxy tar is a very common product supplied by almost all marine paint manufacturers. Google it!

[mako]

I wasn't referring to epoxy tar but to actual hot, melted tar like the stuff you spread on your flat roofs or build shower pans out of. The sleazy "repair" to inside corrosion in a steel boat is to pour it into the spaces. The PO of my boat did that. The problem is that you can't see it. You have a nice flat or smooth surface that is black, in the deep recesses of the bilge. In my case it was the forefoot and the area was painted black as well. Survey didn't pick it up. Had to burn it out. Nasty.

[Standbly]

Originally Posted by makobuilders

I wasn't referring to epoxy tar but to actual hot, melted tar like the stuff you spread on your flat roofs or build shower pans out of. The sleazy "repair" to inside corrosion in a steel boat is to pour it into the spaces. The PO of my boat did that. The problem is that you can't see it. You have a nice flat or smooth surface that is black, in the deep recesses of the bilge. In my case it was the forefoot and the area was painted black as well. Survey didn't pick it up. Had to burn it out. Nasty.

That is nasty! Hope you got it out and the steel wasn't too bad.

Concerning the epoxy tar, I was referring to Hellosailor who said: /quote "Coal tar epoxy?? Coal tar is one thing, epoxy is another. Sounds like mixing fresh sushi and lean hamburger: A perfectly good waste of two good materials combined that way." /Unquote

[hellosailor]

Tar can actually be a damned good sealer. Some of the best gasket sealers used to be a tar product. Withstood chemicals, didn't migrate...traditional for steel in places where it doesn't have wear issues and such. I'd expect that someone didn't clean the steel, or didn't pour enough tar, and from what you said, someone then just used black paint the next time around with predictable results.

Tar is one of those things where if you ask the pros how to remove it they just smile and say "Oh that's easy, mechanical removal." Right, coupla underpaid guys, some scrapers, lots of rags and solvent...Easy, right.

[RaymondR]

Originally Posted by hellosailor

Tar can actually be a damned good sealer. Some of the best gasket sealers used to be a tar product. Withstood chemicals, didn't migrate...traditional for steel in places where it doesn't have wear issues and such. I'd expect that someone didn't clean the steel, or didn't pour enough tar, and from what you said, someone then just used black paint the next time around with predictable results.

Tar is one of those things where if you ask the pros how to remove it they just smile and say "Oh that's easy, mechanical removal." Right, coupla underpaid guys, some scrapers, lots of rags and solvent...Easy, right.

My steel boat had a very difficult to access place where the hull plating met the stem bar. It was a deep, narrow V shaped slot which ran all the way down from the stem to the first frame. In 1986 whilst fitting the hull out and after cleaning it out thoroughly I slowly poured molten tar into the slots whilst heating the metal with a hot air gun. In late 2011 whilst carrying out a hull refit I cleaned out a number of short sections to check for underlying corrosion, there was non and I remelted the tar back into the places where it was disturbed. You need to get the hot tar to wet the metal before it cools to get good adhesion so that water cannot access the metal's surface.

Used appropriately it's an excellent corrosion preventive agent for steel boats.

[Raggedglory]

Originally Posted by makobuilders

Tatheelrod22, word of advice. Find the deepest, darkest, nastiest corner of the bilge. Usually deep in the forefoot under a tank, or below the packing gland. If you investigate and it's filled with what was once hot melted tar, then run for the hills. Sleazy scam artist seller.

Only a fool would buy a boat like that. Don't ask me how I know

Could you please expand on your statement?
Was this tar put there to hide corrosion which would otherwise not be visible or did putting this substance in as a supposed preventative measure perhaps cause water to be trapped causing corrosion?
Your comment struck me with concern as i just bought a steel boat and the only place which does have this tar is under the packing gland.
The boat is 39 yrs old and the majority of the steel hull looks in great condition.
I just removed the volvo md11c and replaced it with a beta 30 so this area was easily visible. Now i' m wondering very interested in your findings.

[mako]

Originally Posted by Raggedglory

Could you please expand on your statement?
Was this tar put there to hide corrosion which would otherwise not be visible or did putting this substance in as a supposed preventative measure perhaps cause water to be trapped causing corrosion?

Good morning. So in my situation the PO definitely poured tar in the spaces to try to hide or slow down existing corrosion on the inside. This was all confirmed by the shipyard and the marine welding team who I hired to repair the works.

Even with the tar, the corrosion continued and reached the exterior. I discovered (after closing) the many hidden little "gems" that the PO left me, so my point of view here is from the sleaziness factor of using tar.

However I have to respect RaymondR's comments above. He describes a legitimate use of tar, applied in a proper manner. Perhaps your situation under your stuffing box is also a proper install, but perhaps not. You could have that particular area audio-gauged the next time you haul out.

In my opinion though, for my next steel boat if there are any hidden, hard to reach areas, then I would prefer to weld them shut like a box. Sandblasting, epoxy primer, coatings and lack of oxygen from a closed space... those are the best ways to protects.

But honestly I'm just sharing my opinion from my own experience, I'm not negating others'.

[Delfin]

Originally Posted by Raggedglory

Could you please expand on your statement?
Was this tar put there to hide corrosion which would otherwise not be visible or did putting this substance in as a supposed preventative measure perhaps cause water to be trapped causing corrosion?
Your comment struck me with concern as i just bought a steel boat and the only place which does have this tar is under the packing gland.
The boat is 39 yrs old and the majority of the steel hull looks in great condition.
I just removed the volvo md11c and replaced it with a beta 30 so this area was easily visible. Now i' m wondering very interested in your findings.

No oxygen, no rust. The only thing paint does is to provide a coating that keeps oxygen from oxidizing the protected metal. Tar, properly applied, is a very durable way of accomplishing the same thing, which is why it is issued extensively in quality boat building. The Dutch, in particular.

It can be used, as Mako unfortunately found out, to perfume the pig, but audio gauging the hull should be a required part of a metal boat survey, and it will tell you whether the tar is covering a problem, or preventing it.

I use Petrotape to wrap all metal fittings and sanitary hoses (to prevent stink). I have a grade 8 bolt at the gooseneck, and stick some Petrotape over the hex head, which would be fully exposed to the sea air otherwise. If I take the tape off, after 12 years, no rust. No oxygen, no rust.

[Raggedglory]

Originally Posted by Delfin

No oxygen, no rust. The only thing paint does is to provide a coating that keeps oxygen from oxidizing the protected metal. Tar, properly applied, is a very durable way of accomplishing the same thing, which is why it is issued extensively in quality boat building. The Dutch, in particular.

It can be used, as Mako unfortunately found out, to perfume the pig, but audio gauging the hull should be a required part of a metal boat survey, and it will tell you whether the tar is covering a problem, or preventing it.

I use Petrotape to wrap all metal fittings and sanitary hoses (to prevent stink). I have a grade 8 bolt at the gooseneck, and stick some Petrotape over the hex head, which would be fully exposed to the sea air otherwise. If I take the tape off, after 12 years, no rust. No oxygen, no rust.

Thanks for your insights. I did have the hull tested by a surveyor and there was 13% loss evidently which i was assured was " nothing ".
I just wondered whether that tar filled bilge section would hide possible corrossion as well as fool the testing.
It makes sense that that area should be protected due to possible water leakage.
The black/brown tar is extremely thick. There is a hole in the section which if water did ingress would spill into the next section which is much deeper and has a bilge pump at the bottom.
Only time i've ever seen water in there was the first trial run after i installed the new motor as the gland nut was loose and spray was happening till i tightened the nut.
Thanks again for everyones input.

[Raggedglory]

Originally Posted by makobuilders

Good morning. So in my situation the PO definitely poured tar in the spaces to try to hide or slow down existing corrosion on the inside. This was all confirmed by the shipyard and the marine welding team who I hired to repair the works.

Even with the tar, the corrosion continued and reached the exterior. I discovered (after closing) the many hidden little "gems" that the PO left me, so my point of view here is from the sleaziness factor of using tar.

However I have to respect RaymondR's comments above. He describes a legitimate use of tar, applied in a proper manner. Perhaps your situation under your stuffing box is also a proper install, but perhaps not. You could have that particular area audio-gauged the next time you haul out.

In my opinion though, for my next steel boat if there are any hidden, hard to reach areas, then I would prefer to weld them shut like a box. Sandblasting, epoxy primer, coatings and lack of oxygen from a closed space... those are the best ways to protects.

But honestly I'm just sharing my opinion from my own experience, I'm not negating others'.

Thanks for your response and insights. I will keep a sharp eye on that area as best i can.

[RaymondR]

One of the better strategies for preventing corrosion in a steel boat is being fanatical about keeping the inside dry.

For many years I battled corrosion in my steel boat. Eventually I realized that the problem would be well mitigated if I became fanatical about keeping the water outside. To this end I replaced the prop shaft gland from a packing type to a Packerless Sealing Systems mechanical type seal and installed a similar disk and plate seal on the rudder stock.

With these two measures about 80% of the water-in-the-boat problem disappeared and it was then largely a matter of fixing any deck or hose leaks to minimize the problem.

[Raggedglory]

Originally Posted by makobuilders

Good morning. So in my situation the PO definitely poured tar in the spaces to try to hide or slow down existing corrosion on the inside. This was all confirmed by the shipyard and the marine welding team who I hired to repair the works.

Even with the tar, the corrosion continued and reached the exterior. I discovered (after closing) the many hidden little "gems" that the PO left me, so my point of view here is from the sleaziness factor of using tar.

However I have to respect RaymondR's comments above. He describes a legitimate use of tar, applied in a proper manner. Perhaps your situation under your stuffing box is also a proper install, but perhaps not. You could have that particular area audio-gauged the next time you haul out.

In my opinion though, for my next steel boat if there are any hidden, hard to reach areas, then I would prefer to weld them shut like a box. Sandblasting, epoxy primer, coatings and lack of oxygen from a closed space... those are the best ways to protects.

But honestly I'm just sharing my opinion from my own experience, I'm not negating others'.

Thank you for your explanation. I appreciate it.

[yttrill]

3mm??? On a 72 footer? RUN! The hull plates should be at least 6mm.

Almost all corrosion on a steel boat will be in the superstructure because of exposure to abrasion and UV which damages the paint, allowing rainwater to get past the paint. There should never be rust inside because there should never be water inside. The usual rust spots are near showers and toilets, kitchen, engine room, and anywhere there's been a spill that wasn't cleaned up.

Rust in the superstructure is easily repaired: grind, paint, grind, paint, and finally cut it out and weld a new piece in. Makes a mess of the interior which has to be removed completely near the repair to avoid a fire when welding.

Interior repairs are very much harder because of access issues. There's no way to get a tool into a corner. Spot blaster is the only way, and that won't work until most of the rust is gone. Usually the welds rust first. You will also get deep pits which cannot be ground out entirely because you'd end up with no steel left. Do the best you can, remove as much rust as possible, and paint, paint, paint.

If you get water in the bilge, after the pump has done its job, use a wet and dry vacuum in wet mode, and then get on hands and knees with rags and remove all moisture. The only place that gets wet that usually is less of a problem is in the engine room because oil spills protect the steel.

Rust in the hull plates is rare because seawater contains a lot less oxygen than air, and because the exterior surface is usually smooth the epoxy undercoat sticks well, and in any case is covered with anti-foul. Chine boats like my Roberts 53 are susceptible to corrosion on or near the chines, but near the waterline is the main issue because of marine growth, turbulence, and strikes from flotsam and dinghys which scratch the paint.

Remember: steel boats are made of paint. The steel is only there to hold the paint up. Its the paint that keeps the water out. And its the paint that keeps the oxygen out. Remember also, 1mm of steel produces 6 to 10mm of rust. So if you see 2mm of rust, you lost around 0.4 mm of steel: nothing to worry about. It looks worse than it is. IF it's the first lot of rust in that spot. The big problem is, rust retains water and O2 and once it starts, its really hard to stop. Paint slows the corrosion rate down by cutting off the O2 supply, but the paint is fractured by even a small amount of rust: that's why it's hard to stop. Typical paint coats are only a few microns, so for repairs use high build epoxy and multiple coats.

As long as the steel is in reasonable condition, the boat will last for ever with maintenance. There are barges in the Dutch canals that are over 100 years old. Of course there's probably not a single piece of the original steel left. Once the steel is generally poor, it is no long possible to repair it properly, you cannot weld rusty steel.

[Delfin]

Originally Posted by yttrill

3mm??? On a 72 footer? RUN! The hull plates should be at least 6mm.

Almost all corrosion on a steel boat will be in the superstructure because of exposure to abrasion and UV which damages the paint, allowing rainwater to get past the paint. There should never be rust inside because there should never be water inside. The usual rust spots are near showers and toilets, kitchen, engine room, and anywhere there's been a spill that wasn't cleaned up.

Rust in the superstructure is easily repaired: grind, paint, grind, paint, and finally cut it out and weld a new piece in. Makes a mess of the interior which has to be removed completely near the repair to avoid a fire when welding.

Interior repairs are very much harder because of access issues. There's no way to get a tool into a corner. Spot blaster is the only way, and that won't work until most of the rust is gone. Usually the welds rust first. You will also get deep pits which cannot be ground out entirely because you'd end up with no steel left. Do the best you can, remove as much rust as possible, and paint, paint, paint.

If you get water in the bilge, after the pump has done its job, use a wet and dry vacuum in wet mode, and then get on hands and knees with rags and remove all moisture. The only place that gets wet that usually is less of a problem is in the engine room because oil spills protect the steel.

Rust in the hull plates is rare because seawater contains a lot less oxygen than air, and because the exterior surface is usually smooth the epoxy undercoat sticks well, and in any case is covered with anti-foul. Chine boats like my Roberts 53 are susceptible to corrosion on or near the chines, but near the waterline is the main issue because of marine growth, turbulence, and strikes from flotsam and dinghys which scratch the paint.

Remember: steel boats are made of paint. The steel is only there to hold the paint up. Its the paint that keeps the water out. And its the paint that keeps the oxygen out. Remember also, 1mm of steel produces 6 to 10mm of rust. So if you see 2mm of rust, you lost around 0.4 mm of steel: nothing to worry about. It looks worse than it is. IF it's the first lot of rust in that spot. The big problem is, rust retains water and O2 and once it starts, its really hard to stop. Paint slows the corrosion rate down by cutting off the O2 supply, but the paint is fractured by even a small amount of rust: that's why it's hard to stop. Typical paint coats are only a few microns, so for repairs use high build epoxy and multiple coats.

As long as the steel is in reasonable condition, the boat will last for ever with maintenance. There are barges in the Dutch canals that are over 100 years old. Of course there's probably not a single piece of the original steel left. Once the steel is generally poor, it is no long possible to repair it properly, you cannot weld rusty steel.

1. I believe it is a 42' boat, as are most all Gazelles.
2. The boat is made of Corten steel, as I mentioned earlier. 1/8" is equivalent to 3/16" steel sheet.
3. Because it is Corten, typical observations about steel and rust are not applicable. Corten is very rust resistant - not impervious, but resistant. It is why it is the kind of steel used in construction where the steel is unpainted. It gets a patina of rust, then it slows down and stops corroding.
4. Those Dutch barges you mentioned that are 100 years old are cast iron. No steel replacement necessary, just a replace a rivet occasionally.

But you quite correct. If a steel point is maintained with appropriate coatings, they last a very, very long time.

[mako]

Originally Posted by Delfin

4. Those Dutch barges you mentioned that are 100 years old are cast iron. No steel replacement necessary, just a replace a rivet occasionally.

I was just thinking that. So where can we buy sheets of cast iron to build our next boat from? How the heck to you weld it?