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

[Delfin]

Originally Posted by makobuilders

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?

All the ones I saw were riveted. Virtually indestructible, but I believe Corten is kind of in between cast iron and mild steel in terms of corrosion. If someone reading the thread has a Corten hull I'd love to hear from them on their maintenance experience.

[Standbly]

Originally Posted by makobuilders

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?

We call the material an old Dutch barge is made off "puddle-iron" It's probably quite similar to cast iron. It's a an early version of what is called steel nowadays. It contains a lot of carbon and unfortunately it rusts. Not as bad as modern steel and certainly not as bad as cheap steel (lots of scrap material). It's brittle but weldable.



One of the reasons Dutch barges last a long time is because of the fresh inland waters of The Netherlands. That and the fact that the hull often lies in the mud in the shallow inland waters, less oxygen in mud.

[Tricolor]

Originally Posted by Standbly

............ It's probably quite similar to cast iron. It's a an early version of what is called steel nowadays. It contains a lot of carbon..........

Nothing to do with cast iron, low carbon, not high, bad welding. Iron is an element while steel is a mix of iron and carbon.

[Juggerknot]

Braze or weld with high silver content rod

[Standbly]

Originally Posted by Tricolor

Nothing to do with cast iron, low carbon, not high, bad welding. Iron is an element while steel is a mix of iron and carbon.

A lot less carbon of coarse, stupid me.

[captlloyd]

Originally Posted by Delfin

All the ones I saw were riveted. Virtually indestructible, but I believe Corten is kind of in between cast iron and mild steel in terms of corrosion. If someone reading the thread has a Corten hull I'd love to hear from them on their maintenance experience.

Forget about both cast iron and Corten. Cast iron does not come in sheets, it is cast and it is brittle, hard to weld, just not suitable for boats. Corten is designed not to be painted, it forms a protective layer of rust on its surface and after that the oxidation stops. Also unsuitable for a boat.

[Lemsteraak]

Yes, the old steel barges in Europe are unpainted on the inside, won't hold a coat of paint. They use a product that is great for applying on rusted steel in the bilge. It penetrates, smells kinda nice, and dries to a soft finish that protects against oxygen and rust. You reapply ever couple years and it makes life with a steel boat bearable.

https://www.toplicht.de/en/shop/yach...oel-hansalux-u

You can order it from Toplicht, it is a not a "yacht" product. Normally sold at the refueling barges that cater to the commercial barge trade.

[Delfin]

Originally Posted by captlloyd

Forget about both cast iron and Corten. Cast iron does not come in sheets, it is cast and it is brittle, hard to weld, just not suitable for boats. Corten is designed not to be painted, it forms a protective layer of rust on its surface and after that the oxidation stops. Also unsuitable for a boat.

Really not sure where you get your information on Corten in boats, but it disagrees with the opinions of boat builders and designers worldwide. Kasten has a pretty good discussion of its use in small vessels here.

As Kasten notes, 1/8" Corten is about as strong as 3/16", which for weight savings is one reason it is so commonly used on smaller boats. Rusts more slowly, but still needs to be blasted, primed and painted.

[hellosailor]

The Wavertree, a tall ship built in 1885 and residing at the South Street Seaport Museum for 30-odd years now, has a hull built of "wrought iron" or "cast iron", depending on who you ask. I suspect the two are the same material. Either way, that WAS a leading edge technology when she was built. These days, they just say "Whatever you do, don't hit that hull, it can't be fixed." Apparently, simple welding is not an option.
But it is proof that even an "inferior" iron hull certainly can hold up for...gee, 134 years now?

[stainless guy]

A36 which is the most common general purpose steel. Has a minimum yield of 36ksi via charpie testing and minimum tensile of 80ksi

A588 "weathering steel" also know as cor-ten under one manufacturer has a min 50ksi yield and min 70ksi tensile. So slightly better with regards to punctures but will be more likely to get impact dents

So hull sheeting and deck from a588 and structural components made from a36 would be the best.

The tradeoffs are not enough in favor of the a588 to reduce material thicknesses

The hull welds would still likely be from er70-s2 which may defeat the purpose of using a588 as that filler material offers no more corrosion resistance than a36

[Arthurwg]

I believe I read somewhere that all steel boats, no matter how well they are painted, treated or maintained, lose a certain amount of material through wastage every year. Is this true?

[Delfin]

Originally Posted by Arthurwg

I believe I read somewhere that all steel boats, no matter how well they are painted, treated or maintained, lose a certain amount of material through wastage every year. Is this true?

Nope.

[RaymondR]

I think the difference between "wrought" and "cast" iron is the shape forming processes.

Wrought is heated and bent or extruded to shape by rolling or hammering and cast is made by pouring liquid iron into a mold. The modification of the carbon content is rendered by oxidation during the heating and reforming process and toughness instilled by the reduction in crystal sizes.