What is the best way to prime steel?

[steve77]

Originally Posted by mvmojo

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

I bought a second-hand bristle blaster off of e-bay. It really does a great job for preparing surfaces. It's a quality tool and well built.

The downside is that it cannot access tight, confined spaces. You need some room to maneuver the tool around to get the proper angle. The belts are available in two widths, but even the narrow belt can't really get into corners. But for any place that you have good access it is awesome.

Cheers!

Steve

[Delfin]

For small spots, I use a Dremel tool, a la dental work, to grind out a spot of rust. Never had a large bit to deal with except on the aluminum superstructure, and there use 40 grit on an orbital sander. In both cases, asap after grinding I use a zinc chromate anti-corrosion primer from Awlgrip. After that, I fill with 3M vinyl ester filler then sand the area being repaired completely flat. Next step is Awlgrip 545 applied with an air brush. No masking generally, unless there is a clear edge to take advantage of or a color change in the repair area. Next is the top coat, again Awl Grip for me, also applied with an air brush. I generally lay on 3 to 5 coats of both 545 and the Top Coat. Finally, wet sand the area with 1,000 grit to take down the overspray on the edges. Last step is fine cut Maquire's rubbing compound to gloss the area to match the surrounding paint.

After 13 years of usage, many people think she was just painted.

[ausnp84]

FWIW, I rebuilt a steel schooner from bare hull and used Jotun paints. The yard sandblasted the entire boat and then I applied three coats of epoxy primer, followed by a topcoat of similar. The work was done during a damp summer and there were some times flash rust would appear. I didn’t bother grinding it - just hit it with the three coats and in six years, never had any rust issues.

Be careful with grinders as they flick rust everywhere and wire wheels are lethal... but they’re both great for clearing areas before applying a good epoxy top coat.

Hope that helps!

N

[ejjawhite]

TwoWords: Coal Tar

[davefrediam]

Originally Posted by hpeer

Thanks for referencing the Monti Tool.

They have 4 different machines. I presume you are using the “Bristle Blaster.”?

The “Die Blasted” looks like it may also have application.

Any further comment/advice would be appreciated.

I mostly use a right angle grinder with flap disks but there are times I just can’t get in there.

Yeah totally agree I have found course grit (40 grade) flapper wheels on an angle grinder by far the best thing for small and medium jobs, far far better than grinding discs. However the finish left is not ideal for paint adhesion so I try to finish off with a small hand sand blaster (just for surface texture) if I have access to a compressor. Also I always use a degreaser (MEK if I got it) which will even take away some of the remaining brown coating you get left with if you can only access an area with wire wheels (a last resort).

Dave

[Paul_Carroll]

On our Colvin Gazelle we have used a zinc based primer (essentially a cold galvanize) paint called Zinga. Works well and seems to last.

https://www.zingausa.com/

[tasssos8]

Originally Posted by chamoy

Hi,
I just bought a 12m steel sloop build in Holland in 1985. No one knew what sort of paint system the boat has. Out on deck it seems like it has a light grey looking thin primer on top of the steel and then a very thick black layer of something very tough that looks like a primer and then paint. Rust is not a big issue, but there are a few places rusting out on deck that I have to tackle.
What is the advice of the experimented steel boat owners out there?
I have heard all sort of ways of doing it, like grinding the steel and 2 part epoxy primer, or sand blasting and 2 part epoxy primer, or just bit of a clean and a rust converter/primer, there is one called Brunox epoxy, that is supposed to by a 1 part epoxy rust converter/primer.
I appreciate any good tips,
Cheers!

Hi there,

I live in The Netherlands and I have a locally made steel motorboat. The usual way treating steel here especially bellow the line is, primer, then, quite often, black Tenco bottom coat (as you described, thick and black) and then a couple of layers of antifouling.
You can treat the small rusted parts with Vactan. First wire brush but leave some rust on.Then apply a good layer of Vactan on it. That converts rust and it is a very good primer too. Then any oil based paint (or black Tenco bottom coat) over it and you are good to go. I just did my over the line repairs and soon I take it out to treat the bottom using the technique I described.

Good luck, those steel sloops are for ever!!!

[MicHughV]

I built a steel ketch back in the late 70's /early 80's.

Protecting the steel was a big issue for me.

No question, # 1 priority is providing a clean surface for the paint to adhere.
This means sand blasting to white metal. An onerous project by any definition.

After blasting, I painted the interior of my boat with a two part coal tar epoxy. This stuff was thick as glue and strong as steel and required 12 gallons to paint the inside of a 38' boat. I'm not sure if this is still available to the general public, but the big ship chandeliers may carry it. It's wonderful stuff. In areas where you can't get too, you can just pour it in...I had some areas, which could not be reached by blasting so I simply just poured the coal tax epoxy in there...and sealed whatever gap there was...
I believe a one part coal tax epoxy is also available, but I have no experience with this product.

The outside of my boat was done with a whole paint scheme. I used a company called Devoe. They can provide you with everything you need. This will start of with a zinc primer, several base coats and then the finish coat. Besides Devoe, there are other paint companies, that can provide the same thing, but I used Devoe and found their product to be very good and easy to apply.

I can tell you, that for as long as I owned that boat, almost 15 years, I never had a single rust problem of note. That boat is still around and still in very good shape, almost 40 years old now.

Once in a while, I would drop something and chip the paint. To patch this area, I would first wipe with a product called Ospho, this will neutralize the rust on the steel, and then I would hit the area with a zinc primer and paint.

When I didn't have Ospho around, I used West System epoxy...marvelous stuff and will cling to anything, including rusty steel. After drying, a quick sand and paint.

The whole objective is to keep moisture, especially salt moisture away from the steel.

99.99% of steel boats will have rust problems on the INSIDE, where water, moisture, etc, will find the smallest unprotected steel component and rust away, often out of sight.

When I sold my boat, the new owners had the hull "sounded" by a surveyor using an ultrasonic device. Nothing out of the ordinary was found anywhere, but I mention this as a tool you could use or have someone do it for you, if you have concerns about the steel thickness anywhere.

Steel is inherently extremely strong, so a little bit of surface rust is generally not a structural issue.

Finally, to overcome my paranoia about dropping stuff on my deck and chipping the paint, I had my entire deck, cockpit, etc, covered with " decktread"....this is a 3/16" thick high grip material that can be purchased in sheets which you can cut to suit and glue in place. I used epoxy glue. The "decktread" can be purchased in a variety of colors.

On my boat I had stainless steel stanchions welded to the deck. On a long ocean voyage, where I had constant spray washing over the boat, the stanchion/hull weld would bleed a little rust. Though the s/s stanchions were welded on with s/s welding rod, there were some areas where the paint system allowed some micro sized rust bleeding. This was more a pain in the rear end than anything else, but on arrival at my destination, I would wash this off.

Like others on this thread, I would sometime use a dremel tool fitted with a metal burr, to clean up a rust spot before using the ospho, etc...

Hope this helps provide some guidance..

[DeValency]

I have a Dutch GRP made (yet, like steel...) boat but a good friend has a Jongert 72’ and we went together through some steel treatment projects. First, remember rust in steel boats start from the inside. - look carefully under the deck and along all areas especially the hatches, chain plates (or whatever it is) and other deck hardware mounts.
Only sandblasting works in peeping the surface! But be ready with the primer immediately.
I had a great experience with International Interprotect 2000E epoxy on my huge iron keel and wings overhaul last year. Looked solid bright and I hated to paint it with the anti fouling. - the finish was outstanding even with a roller but if you can power spray, you’ll get even better results, especially in tight corners and areas that are always more sensitive to rust. (The paint is very thick).
I would say at least four costs of the primer - follow the instructions very very carefully!
After that you should be good to go with any appropriate topcoat - verify that it works well with the primer - it is a known issue.

Enjoy!

Originally Posted by chamoy

Hi,
I just bought a 12m steel sloop build in Holland in 1985. No one knew what sort of paint system the boat has. Out on deck it seems like it has a light grey looking thin primer on top of the steel and then a very thick black layer of something very tough that looks like a primer and then paint. Rust is not a big issue, but there are a few places rusting out on deck that I have to tackle.
What is the advice of the experimented steel boat owners out there?
I have heard all sort of ways of doing it, like grinding the steel and 2 part epoxy primer, or sand blasting and 2 part epoxy primer, or just bit of a clean and a rust converter/primer, there is one called Brunox epoxy, that is supposed to by a 1 part epoxy rust converter/primer.
I appreciate any good tips,
Cheers!

[RodBan]

I’ve had as steel boat on the water for 15 yrs and the best thing Ever that I used was MCU Coating’s Internationa’s, Miozinc primer, Miomastic intermediate coat and MCU topcoat. it’s a single pack moisture cured urethane that loves humidity, is extremely surface tolerant, can be applied over any other product with only fairing it in to achieve a smooth surface. Another advantage is it adhere’s to stainless (if you get it on your hands clean it off as soon as you’ve finished, because if it dries, there is no solvent that can remove it) so where I welded my staunchion bases, chain plates, etc, I just painted 1/2 an inch up the stainless and have never had a problem.
This product is used extensively in the petrochemical industry amongst others as it is acid resistant and extremely hard wearing and the Mcu clearcoat is totally UV resistant and will last for years

[col50]

I don't believe Coal tar epoxy has been outlawed. It appears to be readily available.
Google it or click on the link.
https://www.grainger.com/product/3XH...g!472573728668!

[dannc]

Originally Posted by col50

I don't believe Coal tar epoxy has been outlawed. It appears to be readily available.
Google it or click on the link.
https://www.grainger.com/product/3XH...g!472573728668!

Thank you. I have read about using coal tar epoxy and wondered if it was still available.


Later,
Dan

[jdecris]

I restored a 1951 Alden Steel Ketch.

The bilges were a mess. In a few spots I had to cut out and weld back in new hull plate.

The very good tool for preparing steel for paint is a needle gun.

The tool I used was a JEX-20 Needle Scaler. I used it for 10s and 10s of hours, went through a set of needles, and it was still going strong. And I sold it on eBay after I finished with it.

Worth every penny. Highly recommended.



https://www.mrmtool.com/Nitto-Kohki-...xoC1kAQAvD_BwE

[tasssos8]

Originally Posted by tasssos8

Hi there,

I live in The Netherlands and I have a locally made steel motorboat. The usual way treating steel here especially bellow the line is, primer, then, quite often, black Tenco bottom coat (as you described, thick and black) and then a couple of layers of antifouling.
You can treat the small rusted parts with Vactan. First wire brush but leave some rust on.Then apply a good layer of Vactan on it. That converts rust and it is a very good primer too. Then any oil based paint (or black Tenco bottom coat) over it and you are good to go. I just did my over the line repairs and soon I take it out to treat the bottom using the technique I described.

Good luck, those steel sloops are for ever!!!

I just found that Tenco does not go over primers!!!! I didn’t know that! That saves me a layer. At the end, a bronze Tenco layer as antifouling is the best to finish all off.

[col50]

Originally Posted by ejjawhite

TwoWords: Coal Tar

You do mean coal tar epoxy - right?