Steel hull maintenance?

[GTom]

I am about to buy my first boat and while doing my research for months just took a step back: what about building materials?

My specific question would be, how long can a steel boat be left alone in a tropical marina, before I have time to jump down for a rust-hunt?

[Captsteve53]

Thats a loaded Question for SURE! (HOW LONG IS A PIECE OF STRING?),

1) Degradation of a steel hull is totally dependent in the first case as to how was she protected from the build and the type of steel used, was it sand blasted?,what type of Primer and top coats (twin pack epoxy/single pack etc)
2) Is the hull successfully protected by the correct grade/amount of Zinc Anodes
3) Is the any stray currents on board seeking to ground
4) Are the thru hulls isolated from the steel (if metallic)
5) Are any dissimilar metal combinations under the water line

After all that the anti fouling used will be the deciding factor on growth patterns,(same as any vessel,

Commercial steel vessels have a normal 25 year life span,

Cheers Steve

[GTom]

Thanks Steve! Internal sandblasting is my worry, if it was done properly or not... Outside it's easy to redo I suppose, but in case the inside of the hull wasn't treated properly I can hardly imagine that a degutting+sandblasting could be economical.

Can a surveyor judge the quality of the internal finish properly? Any tools to show if there is a proper zinc layer everywhere?

[Captsteve53]

Originally Posted by GTom

Thanks Steve! Internal sandblasting is my worry, if it was done properly or not... Outside it's easy to redo I suppose, but in case the inside of the hull wasn't treated properly I can hardly imagine that a degutting+sandblasting could be economical.

Can a surveyor judge the quality of the internal finish properly? Any tools to show if there is a proper zinc layer everywhere?

There are indeed paint thickness gauges and these days very good ultra sound equipment that dosent even need the paint to be removed and in fact can be used under water, A good ultra sound test on the out side should show any bad area's which can be followed up from both out side and inside,

Interior inspections can be problematic due to so many fixed items where you can not get to, couple that to the fact numerous steel vessels are coated with insulation either sprayed or fixed by adhesive - this is normally done above the water line, so a good visual inspection below the water line normally reveals any issues,

If getting a Survey done look for a surveyor with small steel ship experience and with the latest ultra sound device(with experience). find that and a good Survey starting with a comprehensive exterior check will usually put your mind at ease,

You assume correctly trying to re blast the Interior is some thing you dont want to get involved with, you dont necessarily need a Zinc coating on the interior many steel vessels are just coated with Epoxy Primers /Coal Tar or similar top coats, saying that every steel vessel I have built we used pre sand blasted /Dimet Zinc coated plates and touched up at the end of every day's welding resulting in longevity,

Cheers Steve (MIIMS-Lloyd's Maritime Surveyor)

[Captsteve53]

Below a couple of pictures as the bad side of steel and the good side

The corrosion on the hull is a twenty year old yacht left sitting for 3 years in a Marina also suffering from Galvanic Corrosion assisted by very bad wiring inside the vessel,

The other shows how strong a steel yacht is! not a leak when happened

Can you imagine any other Yacht Material absorbing that impact and not being at the bottom of the sea?

Cheers Steve

[gjordan]

Steve, have you seen dry-ice blasting? I have seen it in an industrial setting but never on a boat. It was great, in that there was no grit left other than what was blasted off. The unit that I saw was a little bigger than a regular commercial sand blaster (and probably more expensive) but in redoing a boat interior it would be so much safer for the existing gear. The dry ice arrived in a big insulated tub on a pallet. Just curious! ____Grant.

[Captsteve53]

Grant:

We have discussed this approach with in the IIMS and took a visit to shipyard (UK) using the technique and was personally impressed with the results but nothing that advanced in the Philippines (Damn it's nearly impossible to find dry ice at all).

The only one draw back was the possible formation of moisture under certain humidity and temperatures (not common) but the hotter the conditions the better, it also aids in the action of breaking down the surface due the thermal difference, There can also be compressor issues if the air is not 100% dry and not to hot-hence why quite often an after cooler is used in the system.

So it can be a little more technical than at first glance, but the advantages i feel far out way any alternative (especially in the clean up process)- Shaving size etc can come into play as well depending on the finish you require,Some painters we spoke to in the yard questioned the finished profile of the steel regarding the grip/key of the surface? compared to normal sand/ steel shot/bead etc

Back to steel yachts for a minute, the main issue with having to blast a interior if suffering from corrosion issues is that you cant get get behind the frames and stringers where quite often the corrosion is at it's worst!

Cheers Steve

[GTom]

These are exactly the two aspects pushing me between FG and steel. It seems I'll start my own cruising life in cold waters (UK) and go even colder (Iceland, Svalbard, maybe Greenland), where whatever happens you don't want to climb in a liferaft. Sturdiness is absolutely a great bonus.

The corrosion side is worrisome, question is how much work is needed to keep it at bay. I'd want a model with a proper zinc layer, which apparently my first candidate is missing

Here is an interesting one, claiming to be built using a corrosion-resistant alloy. The tricky part here is if you weld/attach anything, you should fetch the exact same alloy...

Originally Posted by Captsteve53

Below a couple of pictures as the bad side of steel and the good side

The corrosion on the hull is a twenty year old yacht left sitting for 3 years in a Marina also suffering from Galvanic Corrosion assisted by very bad wiring inside the vessel,

The other shows how strong a steel yacht is! not a leak when happened

Can you imagine any other Yacht Material absorbing that impact and not being at the bottom of the sea?

Cheers Steve

[Captsteve53]

Yes, well if planning to go to those lovely ice bound places a steel hull would be paramount,

If you can look around for a yacht made out of Corten Steel they are normally in great shape and subsequent coatings are not quite as essential, this is the same steel shipping containers are made from, Corten steel, is a group of steel alloys which were developed to eliminate the need for painting, and form a stable rust-like appearance if exposed to the weather for several years.

They add copper /chromium to the mix when brewing up,

All that said there's plenty of good steel yachts out there with out zinc, and the Dutch are steel masters in small vessels so have a look on there wed sites, the added advantage is due to most people these days want GRP steel second hand yachts are cheap by comparison,

My first yacht as below (some thirty years ago) and over 20 steel built since

Cheers Steve

[Captsteve53]

Here's another one for sale using the same steel https://www.boatsonline.com.au/boats...dt-orca/205599

For sure these are Corten steel and therefore would be good buys (after a Survey of course)

No problems with welding at all, and if adding any thing add it in stainless steel, it will weld right on with no issues at all, as i said all containers are made from this steel

Cheers Steve

[GTom]

Originally Posted by Captsteve53

Here's another one for sale using the same steel https://www.boatsonline.com.au/boats...dt-orca/205599

For sure these are Corten steel and therefore would be good buys (after a Survey of course)

No problems with welding at all, and if adding any thing add it in stainless steel, it will weld right on with no issues at all, as i said all containers are made from this steel

Cheers Steve

Nice one, thanks! Seriously considering to go to the other end of the World for a decent boat now. Anyone making boats from proper 316 marine grade steel?