What is the best way to prime steel?

[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!

[slug]

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!

Always best to do it the hard way ...sandblast , prime and paint

When this is not possible you use a “ surface tolerant “ paint

Several around

https://north-america.international-pc.com/product/bar-rust-235

Devoe bar rust is common on ships

Also used in industry ..pipelines , tanks ....

[hpeer]

Pandora’s box there my friend.

Supposedly you need to take the steel back to “near white metal”. Although I’ve never heard a definition of that.

It’s not always possible Unless you want to devote your life to boat restoration.

When doing bigger jobs I use Ameron 2 part epoxy, the “Bar Rust mentioned above. But they are a bitch in small batches.

There is a paint called POR-15 that essentially uses an acid converter and then a 2 part urethane. It can be had in very nice small containers for little jobs.

I’ve been using Petit Rust-Loc, a one part urethane steel primer with a very high aluminum dust content. Can be applied in cold weather, dries quickly, but you need 5-7 coats. It’s a silver color. We have done our deck in this which gives us a silver Grey topside. The plus is that whenever there is a repair we just use the primer and it matches the rest of the deck, sort of. For anti-skid apply the top coat heavy and cover with sugar. Let dry and wash off the sugar.

I scrape of any loose rust, then beat off any adhered rust so that your down to good metal. Then do the acid thing, Ospho. Wash. Let dry. Paint.

It also helps to lower your standards of beauty, it’s a tough steel boat. Think if it as a prize fighter, not a ballerina. Be proud of the wrinkles!

There is lots of prep advice I’m leaving out.

It’s a compromise between doing a better/perfect job and finding time to sail.

[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.

[PaulvR]

I think the thick black stuff may have been (coal) epoxy tar?? It was the bomb, now banned. If so, it will be hell to get off, burn and blast or leave it on :-) !

[mikecambrai]

When you do rub down to bare metal make sure that you apply the first coat within 15 minutes as a fine oxide is formed very quickly. If you don't do that, what ever you choose to apply will not last as long as it should.
Choose the primer that you prefer followed by an undercoat which gives substance to the surface.
Most paint manufacturers give good guidance as to how to use their products and which one you choose will probably depend on your own preference and what is available locally.

[dannc]

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.

Tom Colvin who knew a thing or two about steel and aluminum boat building, built quite a few metal boats, and wrote a few books on the subject, talks about coal tar epoxy in 1985 and 1986. Klingel wrote a book in 1973, that included Colvin talking about aluminum construction, which talks about coal tar epoxy. The stuff has been around a long time.

Later,
Dan

[s/v Jedi]

Originally Posted by dannc

Tom Colvin who knew a thing or two about steel and aluminum boat building, built quite a few metal boats, and wrote a few books on the subject, talks about coal tar epoxy in 1985 and 1986. Klingel wrote a book in 1973, that included Colvin talking about aluminum construction, which talks about coal tar epoxy. The stuff has been around a long time.

Later,
Dan

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

[rmlarson1098]

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. I'll pass on the primer issue, and move to the grinding which you mentioned in passing. Along with grinding wheels, pick up several wheel brushes. I would always start with a wheel brush - a circular wire wheel that threads onto the grinder - before I put a grinding disc to the steel. Use the grinder & wheel 'on edge'; turn the grinder 90 degrees from the flat position to clean with just the edge of the wheel-brush. Using it in the flat position is risky; every time you make contact with something it's likely to 'buck' and try to get away from you.
No need for a stainless steel brush unless you'll be working on S.S.
Resist the temptation to buy a big 10" grinder. A 4" (or 4.5") angle grinder does pretty much the same work and is MUCH easier to handle.
Wear safety glasses (real ones) and if possible a face-shield or goggles. Wheel brushes do eject wires, and at 6000+ rpm they will put your eye out.
If you buy budget grinders expect to go through a few. I still use 20 year old Bosch, which has gone thru dozens (hundreds?) of grinding and cut-off wheels, as well as plenty of wire wheels. The Bosch has metric threads though, and it's hard to find wire wheels to fit.
Metabo is a favorite, a fine (and $$$) tool that should last a long time. I've seen many other 'name brand' grinders burn up in a day.
If power-brushing doesn't remove all the rust, you could try a sanding disc, and if that won't make it a grinding disc. Love steel boats! Best of luck to you.

[nortonscove]

I will second the POR-15 advice. Use it to touch up my cast iron keel and in 7 years have never seen a spot covered by it reappear.

[chamoy]

a Big Thanks to every one that posted an advice !
Now is time to get this moving, perfect ocupation on a world Pandemic !

[sy_gilana]

Brunox is incredible stuff.
90% of the job is preparation.

[s/v michaela]

I have a big steel ketch and have been chasing rust for many years,,, this is what owners of steel boats do in their spare time. Granted that sand blast, prime and paint is the gold standard, it's not always possible. Depending on the size of the job and location, I use a variety of tools. The best being A Monti tool (a mechanical sandblaster which puts a 1 to 3 mil profile on your steel), and the worst being wire wheels( which usually leave a surface that paint wont adhere to for long). Sometimes I need a grinder, a dremel with tiny diamond bits, a sander, a needle gun, air chisel or a chipping hammer.
Think of your boat as a car,,,, they are made of steel ..right? So most of the time you can treat the cabin top and external surfaces just like you would do body work on a car. Now, that being said,,, the products used are just a bit different to combat the harsh salt water environment. Rust converters, be they phosphoric acid, tannic acid or others are good,, coal tar epoxy is good depending on your existing paint system,, two part epoxy primers ie; (PPG Ameron), Evercoat non shrinking putties and spot putties,, System Three fairing compounds or the longer curing Awl Fair,, and again depending on your existing paint system, Awl Craft, Awl Grip, Sterling(sucks), Dupont and a host of other good brand name paints.
You just need to dig in and start doing it,and brush up on your welding skills. You will eventually find what works for your boat and location. And talk to "steel boat guys" they will help "flatten" your learning curve... don't bother with the fiberglass boaters... they are only guessing... unless they work in a body shop!

[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.

[hpeer]

Originally Posted by s/v michaela

I have a big steel ketch and have been chasing rust for many years,,, this is what owners of steel boats do in their spare time. Granted that sand blast, prime and paint is the gold standard, it's not always possible. Depending on the size of the job and location, I use a variety of tools. The best being A Monti tool (a mechanical sandblaster which puts a 1 to 3 mil profile on your steel), and the worst being wire wheels( which usually leave a surface that paint wont adhere to for long). Sometimes I need a grinder, a dremel with tiny diamond bits, a sander, a needle gun, air chisel or a chipping hammer.
Think of your boat as a car,,,, they are made of steel ..right? So most of the time you can treat the cabin top and external surfaces just like you would do body work on a car. Now, that being said,,, the products used are just a bit different to combat the harsh salt water environment. Rust converters, be they phosphoric acid, tannic acid or others are good,, coal tar epoxy is good depending on your existing paint system,, two part epoxy primers ie; (PPG Ameron), Evercoat non shrinking putties and spot putties,, System Three fairing compounds or the longer curing Awl Fair,, and again depending on your existing paint system, Awl Craft, Awl Grip, Sterling(sucks), Dupont and a host of other good brand name paints.
You just need to dig in and start doing it,and brush up on your welding skills. You will eventually find what works for your boat and location. And talk to "steel boat guys" they will help "flatten" your learning curve... don't bother with the fiberglass boaters... they are only guessing... unless they work in a body shop!

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.