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Old 17-04-2020, 11:02   #46
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Re: What is the best way to prime steel?

I used coal tar epoxies for many years in SE Asia w great success. Economical and effective with one proviso: part of its success is due to the tar, which exudes oils that most finish coats cannot bond to. They just peel off after a week or so. So if you use coaltar paint of any kind, or paint over it, you must do so with a compatible paint. If had a hull w a mostly usable coaltar base coat, I'd blast the bad spots and continue on with the coal tar system. CA
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Old 17-04-2020, 11:30   #47
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Re: What is the best way to prime steel?

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I used coal tar epoxies for many years in SE Asia w great success. Economical and effective with one proviso: part of its success is due to the tar, which exudes oils that most finish coats cannot bond to. They just peel off after a week or so. So if you use coaltar paint of any kind, or paint over it, you must do so with a compatible paint. If had a hull w a mostly usable coaltar base coat, I'd blast the bad spots and continue on with the coal tar system. CA
Yah

Coal tar is not the best choice

Bleed thru and adhesion problems

Modern primer systems are superior
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Old 17-04-2020, 11:51   #48
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Re: What is the best way to prime steel?

We drug anchor on a first cruise with our most recent boat. Hit a 70' steel cutter. Guy was homeward bound to NZ finishing a 10 year cruise.

We were ashore, him an another guy moved our boat and re anchored. Broke our swim ladder mounts and scratched his paint a bit.

By the time we arrived with a handle of Mount Gay rum to apologise, he was already at work in the dinghy with the commerical grade Dremel tool and 2 part primer.

He then said, no worries and we have plenty of rum from Barbados so we drank the rum ourselves!
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Old 17-04-2020, 11:53   #49
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Re: What is the best way to prime steel?

Is "Coal Tar" still a thing? Brands? I know VC used to make a like 7:1 epoxy one of some sort.

Heard it also works good to prime a ferro boat under the waterline
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Old 17-04-2020, 19:48   #50
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Re: What is the best way to prime steel?

Many years ago I was rowing through the anchorage in Vero Beach FL and there was a gentleman on deck working on his boat. I waved, no response.

Couple days later going by I waved and called hi - no response. OK, fine, no worries.

The next week rowing in I gave it one last try - and the gentleman looked up from his tools and said to me - "son, can't you see I have a steel boat here? I stop for one damn minute to talk to you and it's going to get ahead of me"
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Old 18-04-2020, 11:09   #51
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Re: What is the best way to prime steel?

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!


I believe this is the one part coal tar epoxy I was referring to earlier.

The stuff I used on my boat was a two part product.

It's quite pricey now....I think back in the day when I built my boat it was around $11/gallon....

Regardless, coal-tar epoxy is wonderful stuff..especially so for a steel boat.

Obviously, some protective gear is called for when applying this product..it is tenacious....will stick to anything...including you...
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Old 20-04-2020, 13:38   #52
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Re: What is the best way to prime steel?

Get the bible of Steel boats, "METAL BOAT REPAIR AND MAINTENANCE A DO IT YOURSELF GUIDE" (sorry dont mean to yell but that is the title) Yachtwork Press by Scott Fratcher
Available as a EBook.

15 year owner of steel boat.
www.camdeboo.ca
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Old 28-05-2020, 19:45   #53
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Re: What is the best way to prime steel?

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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 used POR-15 as well with pretty good results. Maybe my surface prep wasn't good enough as rust has returned beneath those spots. However, all I got was a single tub grey paint, not 2-part?


My current welder swears by Altex Ultra Lock, which is a 2-part primer. I'm giving that a go now to compare.





Quote:
For anti-skid apply the top coat heavy and cover with sugar. Let dry and wash off the sugar.

That's the first time I've heard about sugar! I'll have to try that soon. So far I assumed a fine layer of sand on the second last coating was the way to go.
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Old 29-05-2020, 04:22   #54
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Re: What is the best way to prime steel?

The sugar method takes some practice and is dependent on the paint. It’s not easy to get right. But if you have to clean up a spot you don’t have the sand fighting you. I’ve also done it in on fiberglassed dingy seats. Worked better there.
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Old 29-05-2020, 06:37   #55
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Re: What is the best way to prime steel?

So the sugar is the nonskid material? Normally I fix a bit of the international non skid additive with sometimes 2 coats and do a 3rd with no grit. A lot depends on how it lays on type of paint, etc.

It seems like the sugar would mostly just dissolve unless fully sealed with atleast one coat of paint?
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Old 29-05-2020, 07:27   #56
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Re: What is the best way to prime steel?

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So the sugar is the nonskid material? Normally I fix a bit of the international non skid additive with sometimes 2 coats and do a 3rd with no grit. A lot depends on how it lays on type of paint, etc.

It seems like the sugar would mostly just dissolve unless fully sealed with atleast one coat of paint?
No, you wash the sugar off, when gone it leaves little craters where it was, a rough surface. The texture is driven by how thick the wet paint was applied and the size of the sugar granulas. The durability is determined by adhesion to the base layer and hardness. Iím using Pettit RustLoc which is over 90% aluminum. When I get it right itís really good. Environmental conditions can be problematic. Too hot here, canít stand on deck, and the paint drys so quick I canít really work with it well.

The sugar thing takes a bit of practice and planning.
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Old 03-08-2020, 14:57   #57
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Re: What is the best way to prime steel?

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If you want to remove old coal tar epoxy give it a coat of Pre-Prime 167.
Iím in a yard specializing in steel. They have recommended Ameron/Devoe Pre Prime 167 to others. Iím still waiting to talk to the yard owner. Iíve been looking at this primer today, not a lot written about it. The little I find is interesting and hopeful. Apparently it is a 2 part that goes on VERY thin, like water. Others have described it as ďcreepyĒ in that it creeps into all the little crevices and attaches itself to the metal, rust included, to seal it in. Recommended for ďless than perfectĒ preparation surfaces.

Iím still not sure of the Recommended application schedule, some recommend two coats hot coated by 235 Bar Rust or similar.

Iím going to give it a go and see how it fairs. Iíll report back in a few years if someone reminds me.

Anyone here have an opinion on this stuff?
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Old 03-08-2020, 16:06   #58
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Re: What is the best way to prime steel?

I've chimed in on this before. I'm a fan of Devoe products, have been using them for 20 years on my steel boat. It really depends on your level of preparation. If you're down to bare steel, you can't beat Cathacoat 302H followed by several coats of Devoe 235 Bar Rust 2-part epoxy then either top coat(s) above the waterline like Amercoat 450HS or ABC bottom paint below the waterline. Pre-Prime is a thin so-called "penetrating" epoxy. The theory is that it will creep into surface irregularities and under the edges of existing coatings to seal everything with epoxy and prevent oxygen from getting to the steel. But, I don't think it does anything to neutralize rust and my experience is that if you paint over rust, no matter what you use, sooner or later it's going to bleed through and continue to rust. The particulate solids in the coating leave microscopic air channels that allow oxygen molecules to sooner or later get to the steel. You need to chemically convert the rust to a non-oxidative substrate before painting over it. This requires an acid. There are a number of products on the market for this. Ospho, POR-15, Corroseal , etc. Actually, Rustoleum Rusty Metal Primer is very good if you're going to top coat with an oil based paint like Rustoleum Rust Stop. They all convert rust and seal the steel to prevent further rusting. I've used Corroseal effectively. Once the rust is converted, you can use Pre-Prime to seal the edges and crevices followed by Bar-Rust 235 and then your top coat. But, with all paints, prep is the key. The closer you can get to clean bright steel then treat with Cathacoat, the longer the job will last. I've seen steel panels that were painted with Cathacoat laying in a yard for 20 years with no rust on them!
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Old 03-08-2020, 18:04   #59
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Re: What is the best way to prime steel?

Mojo,
Thanks for that. Makes a lot of sense. I’ve been wondering about the acid.
Do you fresh water wash it before painting?
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Old 03-08-2020, 19:05   #60
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Re: What is the best way to prime steel?

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Mojo,
Thanks for that. Makes a lot of sense. Iíve been wondering about the acid.
Do you fresh water wash it before painting?
I've never seen any directions on any of the rust neutralizers calling for a fresh water wash. Corroseal specifically says to allow 24 hrs to dry before painting. Can't remember exactly what Ospho says, but it's similar. Most of them are water based so they want time for the water to totally evaporate before adding a sealant like paint.
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