Corten Steel

[HVYJimmy]

i believe Corten Steel only surface rusts than seals itself like aluminum , so it doesn't blister like mild steel ,witch sounds good to me . is there a negative side to the story ?

[stillbuilding]

Corten is marginally more difficult to shape and bend.

Will still corrode from electrolysis underwater.

I think it does hold up better with rust. Tends to get a flakey surface scale which is somewhat self protective.

Difficult to find in Australia at times - had to source mine from NZ at that time.


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[Hydra]

Jimmy,
I don't see the gain you expect from using Corten steel on a boat. The protective layer isn't airtight as on aluminium, so rusting still happens, especially if there is salt in the water. I wouldn't have steel with some copper in the alloy on my boat.

I suggest you look at https://en.wikipedia.org/wiki/Weathering_steel

Alain

[Gone Gypsy]

Wow! A boat metallurgy question! Indeed Corten is a copper bearing steel that improves the atmospheric (not salt water) CORrosion resistance by factor of of TEN. The copper changes the outer rust layer to reduce, not eliminate, further rusting in normal exposure to rain and open air. It only works if you let it thoroughly rust and do not remove that outer rust layer. It has minimal resistance to initial rusting. Looks rustic while being functional (10x longer than unprotected steel) for the exterior of buildings - if you let it uniformly and thoroughly rust. No paint, no buff, no scratch. See the Deere & Co world headquarters (where I work as a metallurgist). If you must have steel boat, you will want to paint it and keep it from rusting, which defeats the entire purpose of Corten. I would save money on steel to use on buffing pads and paint.
Fair Winds, Mike


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[HVYJimmy]

thanks everyone
it would seam cor-ten steel isn't as good on boats as i had been lead to believe

cheers

jimmy

[Stumble]

Originally Posted by HVYJimmy

thanks everyone
it would seam cor-ten steel isn't as good on boats as i had been lead to believe

cheers

jimmy

As a rule the Marine market has probably tried everything at least once. Unless there is a substantial change in new materials, technology, or cost it is incredibly difficult to come up with a new fundamental idea.

This goes double for anything that would act to reduce or eliminate corrosion. The cost of salt water corrosion is so high anything that may work has been tried, and there are very good research studies out there indicting the effects. Even something as expensive as a boat built entirely from titanium has been done.

The titanium boat btw was a huge success.... But massively expensive. It would actually be a cost effective option, but only if you assume a service life of >150 years.

[HVYJimmy]

Originally Posted by Stumble

As a rule the Marine market has probably tried everything at least once. Unless there is a substantial change in new materials, technology, or cost it is incredibly difficult to come up with a new fundamental idea.

This goes double for anything that would act to reduce or eliminate corrosion. The cost of salt water corrosion is so high anything that may work has been tried, and there are very good research studies out there indicting the effects. Even something as expensive as a boat built entirely from titanium has been done.

The titanium boat btw was a huge success.... But massively expensive. It would actually be a cost effective option, but only if you assume a service life of >150 years.

i believe some Russian subs were made of titanium

[garrobito]

Originally Posted by HVYJimmy

i believe some Russian subs were made of titanium

Akula type.. I think no one still on service...

[ryon]

Originally Posted by HVYJimmy

i believe some Russian subs were made of titanium

American too! I remember seeing a huge titanium frame waiting to be shipped from one of my customers, back in the nineties. I doubt it was for corrosion resistance though.

[s/v Beth]

There were a few boats made of Nickel alloy- no bottom paint ever. That would be the one I would want

[roverhi]

Corten is more corrosion resistant than mild steel but still needs to be painted to last in a marine environment. About 40 years ago Corten roofing and steel in general was trumpeted as the solution to our salt rich environment here in Hawaii. They sold uncoated Corten steel as the answer to galvanized roofing. In practice had a nice patina but unfortunately rusted through in a few years. They built Aloha Stadium in Honolulu out of Corten Steel and it's been a nightmare to stay ahead of the corrosion issues.

I would build a boat out of Corten in preference to mild steel but it's not an answer to the corrosion problems of steel. Just a way to delay the inevitable with steel construction.

[Pelagic]

My 33 year old Dutch built Corten Steel boat is in fantastic shape, but...A few truisms:

1....Steel boats rust from the inside out.
2....The quality of your coatings at Construction will pretty much dictate the lifespan of your hull.
3....Corten Steel will definitely help to preserve any improperly coated or damaged interior steel in those hard to reach places.
4.....Corten Steel's strength to weight ratio is better than normal boat building steel, so you can build with smaller scantlings for a lighter displacement.

[dannc]

Kasten has a good write up on the good and bad points of various metals, Metal Boats For Blue Water - Kasten Marine Design, Inc.

Corten has greater strength than mild steel but it still has to be prepped and painted like steel.

If only we could afford a hull built of Copper Nickel or Monel....

Later,
Dan

[Ukeluthier]

Originally Posted by roverhi

Corten is more corrosion resistant than mild steel but still needs to be painted to last in a marine environment. About 40 years ago Corten roofing and steel in general was trumpeted as the solution to our salt rich environment here in Hawaii. They sold uncoated Corten steel as the answer to galvanized roofing. In practice had a nice patina but unfortunately rusted through in a few years. They built Aloha Stadium in Honolulu out of Corten Steel and it's been a nightmare to stay ahead of the corrosion issues.

I would build a boat out of Corten in preference to mild steel but it's not an answer to the corrosion problems of steel. Just a way to delay the inevitable with steel construction.

Indeed.

I used to work in a building that was sided in unpainted Corten steel panels when it was built with the promise that it would be maintenance-free and last practically forever. The panels rusted through inside of 10 years and had to be replaced with painted panels.

And this was 20 miles from the nearest salt water.

[puffcard]

Worked on a Corten steel boat for years, became very impressed after getting suck in 3in of ice way up in the Potomac. It does rust and you need to stay on it. It just didn't seem to get out of control as fast with the big blisters of rust like the mild steel boat. When the owner built the new boat the cost of the Corten steel was prohibited. While the Corten is very strong it's less flexible and will crack before the mild steel. I know there are more knowledgeable people here, I was just so impressed with the Corten and it's strength.