What is the best way to prime steel?

[Scorpius]

I'm assuming spot touch ups here, not whole boat - which is best left to professionals. This is the regime on Scorpius (after MANY years of advice, trial and error):

1. Sandblast. You can get small sandblasters that only need a 10 cu.ft./minute compressor (at 100psi). Nothing else gives you as good a surface or can get into the corners.
2. Three coats of POR-15 primer. The first goes on IMMEDIATELY after blasting (it helps to have two people: one blasting and the other wiping down with solvent then painting on the POR-15. Do the first coat one afternoon, the second the next morning, and the third that afternoon (minimum 4 hours between coats, maximum 16. If it sets hard the next coat won't stick properly).
3. One coat of POR-15 transition (Top coating won't stick to POR-15 primer very well without this).
4. Three coats of your favourite top coat. I've used Interlux Briteside for 35 years and am quite happy with it.


Be REALLY careful with POR-15. NOTHING takes it off skin or anything else. If you close a metal can of it with only a few drops on the rim you will never open it again. You will have to destroy the can and pour the remaining into a new container. I keep a few new, clean paint cans (you can buy them at any paint store) around for just that purpose.


This regime takes about a week to get through but, in my experience, you will never have to worry about those areas again. It's well worth it. STEEL RULES!

[hpeer]

Originally Posted by mvmojo

If you want a long lasting fix, for decks and topsides as well as bottoms, I favor a paint schedule using DeVoe/Ameron/PPG products - I think PPG owns them all now. As with all painting, prep is the key! Grind down (or blast) to bare steel to remove all rust. For grinding, I recommend a stainless steel wire wheel unless you want bits of wire rusting on your deck or you're meticulous about vacuuming after grinding. For the first coat, prime with Cathacoat 302H. This is a 2-part inorganic zinc-rich primer designed to provide cathodic protection. Put it on the same day you expose the bare steel, don't allow oxidation to occur overnight. I've seen steel coated with Cathacoat only sit for years outside and not rust!

Next, apply 2-4 coats of Amercoat 235 (formerly called Bar Rust 235). This is a two part phenalkamine epoxy and is widely used in the marine industry to protect steel boats and structures. Put on thin (as you should) it's pretty fast drying especially on a warm day, so you can get several coats in a day. Mix in small batches. Cover the leftover paint and put it in the fridge and you might get another coat or two out of that batch - each coat only needs to dry until it's tacky. Once all coats have dried overnight, top coat with any good polyurethane topcoat. I've had good results with Amercoat 450 HSG, a semi-gloss polyurethane. You can mix non-skid particles in this if desired and it comes in a wide variety of colors or can be custom tinted. Note, for bottoms, skip the topcoat and apply several coats of PPG ABC3 bottom ablative bottom paint. This is a commercial ship grade 5 year paint. I've had great success with it for the past 20 years!

Of course if you want a shortcut quick fix, grind the rust down, coat with Rustoleum rusty metal primer than top coat with several coats of Rustoleum. I paint all my railings with Rustoleum and get 8-10 years or more out of them before they get a little chalky looking and need another coat.

I have one caveat to this above method. First I completely agree with this when doing a whole bottom job.

HOWEVER, I did this, sand blast right on up. And the epoxy started to blister within 6 weeks. Without being I the water. Very long and painful story short........ I now believe that the culprit was a refinery a few miles away.

Whenever I did this paint schedule at this particular marina I had failure. Everywhere else I had good success. On the same boat. So it is something related to that marina. Ameron kept meaning I was getting acids on the steel. No if, and, or buts. Acids in the steel. The only thing that makes sense is the refinery.

[s/v michaela]

Originally Posted by mvmojo

If you want a long lasting fix, for decks and topsides as well as bottoms, I favor a paint schedule using DeVoe/Ameron/PPG products - I think PPG owns them all now. As with all painting, prep is the key! Grind down (or blast) to bare steel to remove all rust. For grinding, I recommend a stainless steel wire wheel unless you want bits of wire rusting on your deck or you're meticulous about vacuuming after grinding. For the first coat, prime with Cathacoat 302H. This is a 2-part inorganic zinc-rich primer designed to provide cathodic protection. Put it on the same day you expose the bare steel, don't allow oxidation to occur overnight. I've seen steel coated with Cathacoat only sit for years outside and not rust!

Next, apply 2-4 coats of Amercoat 235 (formerly called Bar Rust 235). This is a two part phenalkamine epoxy and is widely used in the marine industry to protect steel boats and structures. Put on thin (as you should) it's pretty fast drying especially on a warm day, so you can get several coats in a day. Mix in small batches. Cover the leftover paint and put it in the fridge and you might get another coat or two out of that batch - each coat only needs to dry until it's tacky. Once all coats have dried overnight, top coat with any good polyurethane topcoat. I've had good results with Amercoat 450 HSG, a semi-gloss polyurethane. You can mix non-skid particles in this if desired and it comes in a wide variety of colors or can be custom tinted. Note, for bottoms, skip the topcoat and apply several coats of PPG ABC3 bottom ablative bottom paint. This is a commercial ship grade 5 year paint. I've had great success with it for the past 20 years!

Of course if you want a shortcut quick fix, grind the rust down, coat with Rustoleum rusty metal primer than top coat with several coats of Rustoleum. I paint all my railings with Rustoleum and get 8-10 years or more out of them before they get a little chalky looking and need another coat.

Great advice with the PPG international paints... I have also had good luck with Amerlock II and Amerseal.. If I'm inside a tank where I have to be breathing I really dont like using phosphoric acids like Ospho but I have found that tannic acid like Fertan is a good rust converter for surface rust....Definitely look into a Monti tool Bristle blaster.. It has really made my life simple...

[mvmojo]

Originally Posted by s/v michaela

Great advice with the PPG international paints... I have also had good luck with Amerlock II and Amerseal.. If I'm inside a tank where I have to be breathing I really dont like using phosphoric acids like Ospho but I have found that tannic acid like Fertan is a good rust converter for surface rust....Definitely look into a Monti tool Bristle blaster.. It has really made my life simple...

While not cheap by any means, the Monti Bristle blaster looks awesome!

[hpeer]

Here is another “pro tip”.

Make sure you do your own bottom prep. It’s the best way to inspect your hull. When you see some funny little thing you will dig into it and watch it hard with a hammer, just to be sure. A paid guy will just slap some paint on it and keep going.

[Riddle]

Have a look at www.tercoo.nl (invented in Holland) It is a special rotary disk to prime and clean steel surfaces prior to painting
Fits any rotary drill or grinder. Available in different sized, Works very efficient, I used it to clean the keel.
It is an alternative if you cannot sandblast.

[Dougtiff]

Year's ago, when i was living in Singapore, a cruiser arrived in a nice steel Sloop, the Australian owner had built the vessel himself, the Sloop had no rust anywhere, i asked how he was able to maintain her in such pristine condition,when a rust problem appeared, he would sand blast the area and immediately coat with epoxy and then top coat, so the thing that was interesting was the sand blasting kit he had built, he had a SCUBA bottle with a regulator attached, from there a hose to a spray paint can, like you would use to say paint a car, but the nozzle was replaced with a small pipe, that would allow sand to pass thru[about 1/4 "],he used beach sand for the abrasive, today i believe one can source the spray unit that is designed for sand blasting[abrasive], anyway, the whole thing was small , easy to use, brilliant i thought.

[Gypsyjon]

Sand blast to white steel followed very quickly with Zinc Chromate paint.

[RaymondR]

Had a steely for 30 years and tried lots of paint systems.

I found that the two packs were great if you could blast and put on a shop primer or some other very thin coat on the blasted steel then hi build it.

Inside in non wear areas I found that a coat of Marine Penetrol followed by a couple of coats of a render of cement and boiled linseed oil worked as well as anything and better than most.

[Lepke]

If you're doing touch up and want to get to clean bare steel, the best stuff I've used is Archoil AR5100. It mixes 15:1 with water and works in 15 minutes (depending on the rust thickness). I use a wet towel or saturated cotton fixed in place. It doesn't harm good metal. I also use it to soak small items, tools, engine parts, etc. Works on brass, bronze and other metal corrosion.

About $30 for 16 fl/oz online archoil.com Maybe on eBay and Amazon.


Long term rust free steel: sprayed zinc coating after sandblasting. 2nd best is epoxy primer.

[GeneM]

I used to work on ships and we would blast to near white then apply inorganic zinc (Dimet Coat) on the blasted steel. That's the grey stuff. Humidity had to be right.

Don't grind or wire wheel. It embeds rust particles in the steel by folding over and encapsulating it.

The black was probably coal tar epoxy.

Spot blast if the rest is good.

[Wotname]

Originally Posted by s/v Jedi

I believe the black tough stuff is a coal tar... I don’t know if they had coal tar epoxy at that time yet.

It certainly was, I used it in the mid 80's!

Originally Posted by s/v Jedi

If it’s coal tar or coal tar epoxy then I would leave it in place where it’s fine because it won’t be better no matter what you do

+1
You can't do better! If it hadn't ben banned, it would still be the goto steel coating IMO.

[RaymondR]

Originally Posted by Wotname

It certainly was, I used it in the mid 80's!


+1
You can't do better! If it hadn't ben banned, it would still be the goto steel coating IMO.

If you want to remove old coal tar epoxy give it a coat of Pre-Prime 167.

[Cheechako]

To fix a few spots, I definitely wouldn't remove that coal tar from anywhere but the spots you repair. The stuff is legendary...

[halcyonv]

Hi, I have been a steel boat owner for more than twenty years so here is the rub:

1. ordinary electric drill
2. set of wire brushes
3. can of cold galvanising paint
4. can of quality sealant primer
5. marine grade top coat, any colour

Have these ready for action at a moments notice, anywhere, any time

When corrosion is spotted, act immediately, main thing is get the cold gal and the primer onto a reasonably bright surface ASAP. You can compress the recommended times to suite the urgency of the job - even to a few minutes in the right conditions

Sounds dodgy? remember all steel boats will rust no matter how flash the lay up

Smile a lot, this is now your life