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Scottydosntknow · 30-03-2022, 05:00

Hi Cruisers

I'm looking for some advice from steel yacht owners, I'm starting to get these specks, rust stains on the inside skin of the hull. what is the best way to deal with these? preferably with out having to repaint the entire boat.

Cheers

MicHughV · 30-03-2022, 05:21

It's unclear whether this rust originated from the hull or some metal grinding done in the area.
However, you first have to brush off any loose rust, then neutralize the remaining rust with Ospho or something similar, but then you'll have to paint it. No other way around it, I'm afraid.

I painted the interior of my boat with a two-part coal-tar epoxy. It goes on really thick and will last forever.

Scottydosntknow · 30-03-2022, 05:34

cheers for the quick reply MicHugeV.

MicHughV · 30-03-2022, 07:18

I built my own steel boat...a Roberts 38....and saw many other steel boats being built..if you do it right the first time, it's usually smooth sailing from there....but if you don't do it right, it's a continual pain in the rear end.

My advice, do one section at a time, and fix it right...I'm a big fan of the coal-tar epoxy (for the inside of a steel hull)...it can be had in a one part as well as two part. It goes on quite thick, and once it hardens it is immensely tough and abrasion resistant.

Condensation is a big problem for steel boats. I had 1" thick foam insulation down to the water line, and never had a problem with this.

My boat is now 40 years old and on it's third owner....still going strong.

I had the occasional rust here and there on the inside, and fixed it as described above.

There really is no quick fix here....it's elbow grease and time...but if you do it right.....you can forget about it.

Not sure what you have available in Australia, but I'm sure you can get much the same stuff as we can in the US

rotrax · 31-03-2022, 12:21

We keep a 1986 Hartley 32 in corten steel in Wellington, NZ.

I found 2 pack epoxy tar on Trade Me, the Kiwi ebay. Fixed a couple of issues quickly and so far permanently.

Good stuff.

Manateeman · 31-03-2022, 15:25

Looks like grinding debris as there is little near the junction of the plates and the stringers. We worry about corrosion where things join not in the middle of a flat plate. You know what to do.
Happy trails.
The manatee crew.

Celestialsailor · 01-04-2022, 08:48

If it's not in one specific area but all throughout the boat, I doubt it is grinding debris. Chances are it is rusting from the hull through the paint. The next step is to scrap an area, gently and see if that is the case. Then decide the next step to take.

SVTatia · 01-04-2022, 11:31

Quote:

Originally Posted by Celestialsailor

If it's not in one specific area but all throughout the boat, I doubt it is grinding debris. Chances are it is rusting from the hull through the paint. The next step is to scrap an area, gently and see if that is the case. Then decide the next step to take.

Celestialsailor is right. Previous steel boat owner here. The paint was too thin or not enough coats. Usually happens if a "pickled" plate was painted without grinding or blasting.
I would not worry about it - a solid coat of epoxy will fix that. Although an excellent rust protector, the problem (my opinion) with coal tar is that it obviously only comes in black, and cannot be overpainted as it is likely to bleed-thru top coats. Black bilges are hard to keep clean...

aqfishing · 01-04-2022, 12:39

That does not look like grinding leftovers. Unfortunately it looks like the paint was not properly applied on a properly prepared area.

No matter what you put over it, you will need to deal with the surface rust. At this point it does not look too bad, so the sooner you tackle it the better. Unfortunately the only way to really do it properly is to sandblast and immediately prime. I am pretty sure you will not want to do this.

A needle scaler also works well.

Your rust may still be such that I light chip and sand followed by a good rust remover could work.

I have owned and worked on many steel commercial fishing vessels….while I have no doubt that steel vessels make better sea boats, my new vessels are all GRP. The rust just killed me!

Good luck!

Celestialsailor · 01-04-2022, 13:20

Quote:

Originally Posted by SVTatia

Celestialsailor is right. Previous steel boat owner here. The paint was too thin or not enough coats. Usually happens if a "pickled" plate was painted without grinding or blasting.

Yup...That mill surface has to be broken. Sand blasting is the only thing I used on the two I built for myself. Blast to white, 2 spray on Strontium Chromate. Then 4 high build red primer. Then LPU or enamel.
A surveyor friend of mine told me that old Dutch Freighters had hot tar poured in the bilges. He popped a sample for a survey. The boat was from the early 60's and he said the steel was very clean underneath.

Fore and Aft · 01-04-2022, 16:18

Scott it is always a shame that a lot of steel boat builders never used a holiday detector or paint thickness gauge. That along with a PSS seal would have prolonged the life of a lot of steel boats I survey.
I have spent countless hours inspecting painted gas pipelines and it always surprises me what defects the eye misses.
Cheers
Holiday Detectors, Porosity Detectors, Pinhole Testers, Jeepers

rotrax · 02-04-2022, 11:29

Quote:

Originally Posted by SVTatia

Celestialsailor is right. Previous steel boat owner here. The paint was too thin or not enough coats. Usually happens if a "pickled" plate was painted without grinding or blasting.
I would not worry about it - a solid coat of epoxy will fix that. Although an excellent rust protector, the problem (my opinion) with coal tar is that it obviously only comes in black, and cannot be overpainted as it is likely to bleed-thru top coats. Black bilges are hard to keep clean...

My Kiwi 2 pack epoxy tar was Gray.

I used it in the gas locker and cockpit.

I have not painted it, the gas locker has a cover, the cockpit a fitted grid.

MicHughV · 02-04-2022, 12:02

The entire interior of my steel boat was painted with a two-part coal-tar epoxy. It was sand blasted first. I never once, had a single problem with rust on the inside of the boat, not once. I also insulated my hull with styrofoam panels down to the water line, for fear of condensation in the winter. If my memory holds, it took 13 gallons to paint the interior of a 38' boat. It goes on really thick.

A subsequent owner stripped the boat down and painted the bilges white. THat boat is now 40 years old.

Retro-painting the interior is going to be a chore, so might as well take your time and do it right, instead of twice.