steel hull repainting

[Aravind]

Hi

I've been getting some info, but I'd like to hear your opinions on what's the perfect treatment for a steel hull.
My proposition would be:

Sandblasting the hull, including the corner area up to the deck. (I'd overlap the epoxy paint to the deck a bit, since the corner is a rust vulnerable area imo).

Free-board:
- 1 layer of epoxy primer
- epoxy fairing if needed
- 3 layers of epoxy paint

Under water Hull:
- 1 layer of epoxy primer
- epoxy fairing if needed
- 3 layers of epoxy barrier coat
- anti-fouling

I'm considering doing an additional 1-3 layers of barrier coat on top of the fairing, but not sure if this is necessary.
kind regards
Aravind

[neilpride]

Sounds good but I would add another coat of the epoxy primer after the sand blast for a total of 2.

Or after the epoxy fairing to seal everything with another coat since it is complicated to do 2 coats after sand blasting.

I would seal the fairing work with primer either way.

[MicHughV]

As an ex-steel boat owner, that I built and painted myself, my suggestion is this.

Stick with one paint company so that all the different coats will be compatible with each other.

Outside of hull.
#1. Sand blasting, yes, off course, this must be done, both inside and outside.
#2. First coat is a zinc primer. You want to put this on within an hour of blasting, so you may end blasting and painting smaller sections.
# 3. Barrier coats, I used a two-part epoxy barrier coat paint. I painted two coats with a light scuffing in between.
#4. My initial final coat was also a two-part epoxy paint, also two coats, so five coats in all.
# 5. Below the water line came two coats of antifouling paint, also by same company.

However, epoxy paints tend to chalk over time, so I repainted the hull with a two-part polyurethane paint. Ironically, the epoxy paint provided a wonderful primer for the polyurethane paint. This is a wonderful paint. It has a very tough finish.

Inside of hull

I could have done the inside just like the outside, but instead opted to use a single coat of a two-part coal tax epoxy. This goes on really thick, and hardens like steel. I used 13 gallons on the inside of 40' boat, just to let you know how thick this paint it.

99% of rust problems on a steel boat start from the inside of the hull. I liked the coal-tar epoxy as I could pour it into hard to reach cavities, like the keel, etc.

That boat, now on it's third owner is over 40 years old, and still looks as good as the day I painted it.

[MicHughV]

that should read "coal tar" epoxy.....not coal tax...my bad..

[Aravind]

I like the idea of the coal tar epoxy for the insides of the hull, especially below the waterline, engine bay etc.
However I like to keep a clean hull and engine bay = keep it white. Should I paint it over with a white epoxy afterwards?

[Aravind]

Can I do the base layers in one go for both sides and bottom?

- Zinc primer (1 layer) International Interzinc 75 (zinc-rich epoxy)

- Barrier coat (2 layers):

International Epoxy Tie-Coat primer

OR

- Seapoxy 73

Is there a reason why I should not use this above the waterline as well? sounds easier to me since I'm doing the whole hull.

[MicHughV]

I left my coal-tar epoxy as is. When it hardens, it gets a very smooth surface, and I didn't think another paint would stick to it.
I like a clean engine room too, mostly ever saw dust in there. I had lights inside the engine room, so could see everything.
I did the entire interior of the boat with coal-tar. From top to bottom. Then I put 1" Styrofoam insulating panels between all the frames, stringers, etc, from the water line up. My boat was remarkably cool. and I never had any problems with condensation, etc.
From the water line down, I had no insulation.

I eventually covered the deck with glued on tread master.

Interestingly, a week or so, after I had painted the inside of the hull with coal-tar epoxy I noticed one section of the inside that I forgot to paint, which was right under the cockpit seat. Not having anymore paint, I covered this with the WEST system epoxy, and it worked like a charm.

[MicHughV]

I got to know several other steel boat builders, that opted to paint the inside of their boats, same as the outside, ie, zinc primer, followed by two coats of base coat, but no final coats, which is an option to consider.

For my money, the coal tar epoxy is a better solution.

[hpeer]

I have spent too much time on this subject. Ask 5 experts and get 8 definite answers. I had a paint job fail pretty badly and spent time trying to suss out the cause and fix. Below are my various comments. I could expound on certain elements if desired.

Zinc base coat, there are 2 competing theories, yes or no. I can understand both arguments. In my experience either will work.

The key to success is having a very clean and neutral surface. My failure seems to he because there was a refinery a few miles away. Despite all my efforts the AIR had acids which got on the metal and which created osmotic blistering BEFORE LAUNCHING!!

I typically use PPG: 302 zinc, 235 rust barrier, 450 top coat. Relatively inexpensive, widely used and available, good support.

You don’t want the coats too thick, as they dry they contract and can pull through the thickness and detatch.

Timing between coats is important, you want to get the subsequent coat on while the first coat is a but deformable. This can be tricky and is highly dependent on temperature.

The rougher the surface the better, more adhesion.

I have discovered the Terco Rotary Blaster. You may want to consider this as an alternative to sandblasting. It does a really good job of paint stripping leaving a good rough surface. There is less mess and not nearly so much equipment or expense. I have not used the 3 disk units but can see they would work well. A typical drill has marginal speed, the higher the speed the better. Maybe mount one an air drill? Anyway, something to consider.


https://tercoo.com/en/everything_you...ating_blaster/

More thoughts on doing interior restoration work if desired.

All for now.

[MicHughV]

I hear ya....my first attempts to paint my hull was a disaster, as I was using non-compatible paints, being as that I was broke.

This, off course, meant I had to do it all over again. I then went to a paint company that provided paint for ships, and they put me on the right track giving me a paint sequence and the right kind of paint, etc.
The paint was made by Devoe. I know that there are other brands, but that is what I used.
After about 5 years, I put the two-part polyurethane paint over the hull.