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Some of your puh-ro-feshunnal folks here may know something about this - or not.  Looks interesting, anyway, for new construction.  But perhaps only for commercial/large scale stuff? 

https://newatlas.com/materials/steel-anti-corrosion-alloy-coating/?fbclid=IwAR3NQQfJZJxyuAaZw5SBhmtaTLaNaDXRXjUCAfeSFsHP21mp6OKijzhOYpc

New alloy coating builds an inner shield to stop steel rusting

January 05, 2022

As useful as steel is, its main weakness may be its vulnerability to corrosion. Researchers in Korea have now developed a new alloy coating that boosts steel’s resistance to rust, by adding a simple extra step in the surface treatment.

Steel is often coated in other metals to improve its corrosion resistance, but the salty marine environment poses an extra challenge. Aluminum is a common anti-corrosion coating, but it itself tends to react with chloride ions in seawater and rust easily.
 

So for the new study, engineers at the Korea Maritime and Ocean University (KMOU) developed a new alloy coating made of aluminum, magnesium and silicon (Al-Mg-Si). The team started with aluminized steel, which is steel that has been hot-dipped in a bath of aluminum and silicon to coat it. The missing ingredient – magnesium – can’t be applied through this method, so the team coated the steel using physical vapor deposition. Finally, the coating was then exposed to a high temperature of 375 °C (707 °F), for different amounts of time.

The team then tested the corrosion resistance of the new coating by subjecting it to a standard salt spray test. They compared versions of the new alloy that had been heated for zero, five or 30 minutes, as well as a regular aluminized steel sheet and a galvanized steel sheet.
 

[cont’d]

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How would one construct anything without destroying the hot-dipped coating at the point of welding or exposing raw steel at the point where it was drilled to rivet or screw it together?  

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8 hours ago, Jud - s/v Sputnik said:

Some of your puh-ro-feshunnal folks here may know something about this - or not.  Looks interesting, anyway, for new construction.  But perhaps only for commercial/large scale stuff? 

https://newatlas.com/materials/steel-anti-corrosion-alloy-coating/?fbclid=IwAR3NQQfJZJxyuAaZw5SBhmtaTLaNaDXRXjUCAfeSFsHP21mp6OKijzhOYpc

New alloy coating builds an inner shield to stop steel rusting

January 05, 2022

As useful as steel is, its main weakness may be its vulnerability to corrosion. Researchers in Korea have now developed a new alloy coating that boosts steel’s resistance to rust, by adding a simple extra step in the surface treatment.

Steel is often coated in other metals to improve its corrosion resistance, but the salty marine environment poses an extra challenge. Aluminum is a common anti-corrosion coating, but it itself tends to react with chloride ions in seawater and rust easily.
 

So for the new study, engineers at the Korea Maritime and Ocean University (KMOU) developed a new alloy coating made of aluminum, magnesium and silicon (Al-Mg-Si). The team started with aluminized steel, which is steel that has been hot-dipped in a bath of aluminum and silicon to coat it. The missing ingredient – magnesium – can’t be applied through this method, so the team coated the steel using physical vapor deposition. Finally, the coating was then exposed to a high temperature of 375 °C (707 °F), for different amounts of time.

The team then tested the corrosion resistance of the new coating by subjecting it to a standard salt spray test. They compared versions of the new alloy that had been heated for zero, five or 30 minutes, as well as a regular aluminized steel sheet and a galvanized steel sheet.
 

[cont’d]

I think that would be neat in air.  Not sure how it would hold up under water given that both Magnesium and Aluminium are good anode materials.  I think I'd rather have zinc flamed if $ was no issue.

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Researchers...sounds mildly interesting. But only if you apply it to fabricated components like a crane foundation or a pump body or something. Obviously when you weld the ship you burn off the coating.

Modern epoxy paints are very very good at preventing corrosion. Stick with 1 supplier's system, follow their application protocols carefully (especially dew points) and you can have a rust free steel boat. But you've gotta be a bit OCD.

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no matter what sort of wondercoatings they have & probably will invent, the main difficulty for the protection of the steel hull is in the preparation & application on the INSIDE of the hull:

the ONLY 100% method is:

sandblast a surface that can be coated in say MAX 3-5 hours, clean up, coat, let dry

sandblast the next portion, clean up, coat, let dry,

& so forth.

IF the interior gets sandblasted at all before coating, this is usually done in one go, then cleaned up, the coated. This means that at least for some of the surface the time interval between blasting & coating has been sufficiently long for - invisible - oxidation to start.

Needless to say: the design of the framing, stringers, that allows any little pocket of water to remain standing without draining away is the devil's... 

 

(& imho: of one goes to all the above trouble (& expense if done by a professional) - one might as well build in aluminium)

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Best solution I have seen is the very large vats where they galvanize the large electrical power poles. A gentleman in the Rockwall, Texas was (may still be)  in the business of building boat trailers and the vat was large enough to also galvanize his trailers.  However, most steel hulls exceed the girth that such a vat and thus not a workable solution.  

Galvanized boat trailers look great in my opinion. That would be compared to painted steel trailers that much sooner than later develop a nice coating of rust and look like a place most Christians don’t want to go.  Horse and Stock trailers and steel bedded wheelbarrows can literally melt before your eyes from the damage that urine can do.  That’s why most modern horse and stock trailers are made from aluminum and any quality wheelbarrow has a composite bed.  (Plastic bedded wheelbarrows are no better than children’s toys) 

Speaking of wheelbarrows, we purchased a good one in 1987.  I have replaced the wooden parts of the frame and the wheel and tire but the galvanized parts of the frame and the composite bed are as good as new (despite three decades of use and abuse) This says a lot about what small to medium sized boats need to be built of.  Steel is strong but composite, when properly built can last pretty much forever (osmotic blistering excepted)

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  • 2 weeks later...
On 1/9/2022 at 8:44 PM, tane said:

no matter what sort of wondercoatings they have & probably will invent, the main difficulty for the protection of the steel hull is in the preparation & application on the INSIDE of the hull:

the ONLY 100% method is:

sandblast a surface that can be coated in say MAX 3-5 hours, clean up, coat, let dry

sandblast the next portion, clean up, coat, let dry,

& so forth.

IF the interior gets sandblasted at all before coating, this is usually done in one go, then cleaned up, the coated. This means that at least for some of the surface the time interval between blasting & coating has been sufficiently long for - invisible - oxidation to start.

Needless to say: the design of the framing, stringers, that allows any little pocket of water to remain standing without draining away is the devil's... 

 

(& imho: of one goes to all the above trouble (& expense if done by a professional) - one might as well build in aluminium)

I had EVERY piece of steel that went into my hull professionally blasted & sprayed with weld-through primer before it was welded into the hull. That way I knew there was no trapped mill scale anywhere and I only had to worry about the heat affected zone rusting. That dealt with the issues of blasting the interior after completion which is never better than a pious hope IMO.

As for light oxidation, simply not a problem if you use paint like Jotun 605 epoxy.

You do need to be pretty meticulous, for sure. I bought an ultrasonic paint thickness gauge to ensure I had at least 400 microns paint thickness on the outside of the hull. The interior probably has more paint as I basically spray-blasted it using a gun designed to apply underbody coatings. I got paint behind every frame and stringer, for sure. Lots of paint runs too. Didn't care, the point was cover & buildup, it was all going to be covered by the insulation & lining anyway.

3 years since launch, more or less, and you could eat off of the hull plate under the cabin sole.

As for the steel versus aluminium discussion, it all depends on what you're prepared to trade off. Steel is a lot more forgiving to work with and a lot easier to get paint to stick to. As for the corrosion issue, a friend of mine has been getting quite a bit of his aluminium 50' design re-plated. Pinhole corrosion you see.

The biggest hassle with a steel boat is keeping on top of the rust bleeds from paint chips and the like. At least it is on my boat. But the Jotun 605 is a 1:1 mix so easy to mix very small quantities - I just use disposable plastic spoons and a small cup. In fact I noticed a paint chip forward from careless anchor handling so I guess it's that time again...

FKT

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I have a (probably irrational) fear of aluminum boats, what with pinhole corrosion under tanks and the ever-present possibility that an errant strand of copper from a cut electrical wire will eat a lovely little hole right thru the hull.  This fear prevents me from lusting after a number of nice-looking new and used aluminum boats, which I probably couldn’t afford anyhow….  So, tell me I’m wrong, please.

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