Rustoleum Cold Galvanizing Compound for exposed metal

[Justus C]

I am replacing the tongue on my trailer and had to have some welding done on the replacement. The new tongue is zinc-plated, but the welds have compromised that coating. I want to apply Rustoleum Cold Galvanizing Compound to the welds to restore the zinc finish, then apply a primer and top coat to the entire tongue. The product claims to leave a film of 93% zinc and provide "maximum rust protection."

Has anyone here used the galvanizing compound on exposed metal parts? Were you happy with the long-term results?

The product label says that no top coat is required, but I am finding some user comments that indicate this is a marketing gimmick. The product website says "for maximum protection, topcoat with Rustoleum finishes."

I've found a post on a boating forum stating that Rustoleum advises if a primer is used over the compound, it should be latex-based because oil-based primers will cause the film to peel. But I have found generic advice that painting over zinc-plated metal requires a primer formulated to etch the zinc, and that using latex-based primer will result in flaking. I have a request in with Rustoleum to clarify which finishes are safe.

Edit to add: I received a response within a few minutes from Rustoleum: "Since the galvanized has zinc a water based primer would need to be applied first. You may consider looking into our Universal bonding primer, which can adhere to zinc. Once the prime is on the surface then an oil based can be top coated. If you have any additional questions or concerns please do not hesitate to contact us."

I found POR 15 recommended as a one-stop-shop for corrosion prevention, but I would rather use a spray product on the tongue to get in all of the crevices. I also don't need a $35 pint of paint that will go bad after I open it or the additional $30 in prep materials that I will only use once.

Am I overthinking this? Since the tongue has never been exposed to the elements and is currently rust-free, could I just use red oxide primer with rubberized undercoating over top and call it a day?

[OCJohn]

Justus – I have not used rustoleum brand, but did recently use a similar zinc/galv spray coating I found at the local industrial hardware store. I used it as a primer and thought it went on and dried out very well. Finesse with spray finishes has never been my forte, so it’s always a victory when I get a solid, even coat without any runs. The one I got also had some amazingly high percentage of zinc. Because of that it requires frequent shaking. I swear I could see the coat density change (as it settled in the can) just 30 sec or so after shaking... So I shook it a lot as I sprayed. I also didn’t think it looked anything like actual galvanized steel. More of a satin primer.

My top coat was rustoleum hammer finish silver which turned out a very close match for galv when viewed from 6 feet or so.

Downside is it’s not nearly as scratch resistant as galv or powder coating. So when I think I’ve run out of tongue area fabrication projects I’m going to pull it all off and find a good local powder coating shop to do it right.

Can’t help you with the longevity question. In general I know that good prep and SOME coating is half the battle. You might ask on one of the really big RV forums like RVnet. I’m sure there’s no shortage of old wise men over there.

[k corbin]

Originally Posted by Justus C

I found POR 15 recommended as a one-stop-shop for corrosion prevention, but I would rather use a spray product on the tongue to get in all of the crevices. I also don't need a $35 pint of paint that will go bad after I open it or the additional $30 in prep materials that I will only use once.
?

There is a easy to do trick to storing the opened can of POR 15 for later reuse. Clean out the groove on the top of the can, wipe the mating edge of the lid off. Then before putting the lid back on the can put a piece of plastic wrap over the opening. That way you will be able to get the lid back off so that you can use the rest of the contents at a later date. If you don't use the plastic wrap the Por 15 in the rim of the lid will cure hard and then bond the lid onto the can. I know this trick works because I have tried it.

[Doug Arthurs]

Originally Posted by k corbin

There is a easy to do trick to storing the opened can of POR 15 for later reuse. Clean out the groove on the top of the can, wipe the mating edge of the lid off. Then before putting the lid back on the can put a piece of plastic wrap over the opening. That way you will be able to get the lid back off so that you can use the rest of the contents at a later date. If you don't use the plastic wrap the Por 15 in the rim of the lid will cure hard and then bond the lid onto the can. I know this trick works because I have tried it.

I was thinking about trying POR-15 on my trailer. The bumper I welded up and coated with truck box liner is already showing rust stains through it. How do you find the POR-15 stands up?

[Raz]

I've used the cold galvanizing paint on my metal roof to touch up rust spots. It runs very easily so multiple light coats work best. It dries flat grey. It has held up quite well on the roof but I'm not sure it would be as durable on anything that is handled. If you try it remember to shake well.

As for POR15, highly recommended, I thought about using it on my frame until I read the can. Shell off frame, perhaps, but on my back under the trailer. Nope. Also, lots of prep work required. I settled for rustoleum primer and paint.

[Doug Arthurs]

Originally Posted by Raz

I've used the cold galvanizing paint on my metal roof to touch up rust spots. It runs very easily so multiple light coats work best. It dries flat grey. It has held up quite well on the roof but I'm not sure it would be as durable on anything that is handled. If you try it remember to shake well.

As for POR15, highly recommended, I thought about using it on my frame until I read the can. Shell off frame, perhaps, but on my back under the trailer. Nope. Also, lots of prep work required. I settled for rustoleum primer and paint.

Ya I was considering it for my frame as well but I am not doing a frame off.

[AC0GV]

Originally Posted by Justus C

I found POR 15 recommended as a one-stop-shop for corrosion prevention, but I would rather use a spray product on the tongue to get in all of the crevices. I also don't need a $35 pint of paint that will go bad after I open it or the additional $30 in prep materials that I will only use once

Keep in mind that POR-15 is a brand name covering 30+ products. Just asking for POR-15 at the store may get the wrong product.

Also spray galvanizing works well as a primer on bare aluminum.

[k0wtz]

looking at our trailer it certainly is showing some rust. Is it dangerous? I doubt it but as soon as I can I am going to sand things down including crawling under it if I can figure out a way.

Wifey found a bunch of disposable brushed I think I am going that way. These products suggested are interesting as I start my quest for something to cover things up.

It looks like a couple of days work to do it but I am going to try! I doubt if any of it will stay for too long a couple of years maybe then the new owner can take care of things!

bob

[SnowballCamper]

Originally Posted by Justus C

Am I overthinking this? Since the tongue has never been exposed to the elements and is currently rust-free, could I just use red oxide primer with rubberized undercoating over top and call it a day?

Yes, and just paint the primer.

Growing up, my dad did all kinds of welding projects around the farm and used rust oleum paint on everything. Depending on the piece we used the standard primer, or the rusty metal primer (of course scraping off any flaking rust). The stuff works great, and never had a problem. Usually did a couple coats...the only hassle is the drying time can be a while depending on the humidity and temp.

[k0wtz]

Justus p/o added around 15in to our trailer tongue you cant believe how nice it is to have that trailer moved back. easier to park and back up too.

bob

Originally Posted by Justus C

I am replacing the tongue on my trailer and had to have some welding done on the replacement. The new tongue is zinc-plated, but the welds have compromised that coating. I want to apply Rustoleum Cold Galvanizing Compound to the welds to restore the zinc finish, then apply a primer and top coat to the entire tongue. The product claims to leave a film of 93% zinc and provide "maximum rust protection."

Has anyone here used the galvanizing compound on exposed metal parts? Were you happy with the long-term results?

The product label says that no top coat is required, but I am finding some user comments that indicate this is a marketing gimmick. The product website says "for maximum protection, topcoat with Rustoleum finishes."

I've found a post on a boating forum stating that Rustoleum advises if a primer is used over the compound, it should be latex-based because oil-based primers will cause the film to peel. But I have found generic advice that painting over zinc-plated metal requires a primer formulated to etch the zinc, and that using latex-based primer will result in flaking. I have a request in with Rustoleum to clarify which finishes are safe.

Edit to add: I received a response within a few minutes from Rustoleum: "Since the galvanized has zinc a water based primer would need to be applied first. You may consider looking into our Universal bonding primer, which can adhere to zinc. Once the prime is on the surface then an oil based can be top coated. If you have any additional questions or concerns please do not hesitate to contact us."

I found POR 15 recommended as a one-stop-shop for corrosion prevention, but I would rather use a spray product on the tongue to get in all of the crevices. I also don't need a $35 pint of paint that will go bad after I open it or the additional $30 in prep materials that I will only use once.

Am I overthinking this? Since the tongue has never been exposed to the elements and is currently rust-free, could I just use red oxide primer with rubberized undercoating over top and call it a day?

[Captleemo]

I have used the Rustoleum cold galvanize many times without any problems. I noticed that the instructions said to use a latex paint for top coating but I top coated mine with regular spray paint and after a number of years it has held up well although you really don't need to put anything over it. I worked in petro-chemical plants for about 30 years and spray galvanize is very widely used in every plant. On the gulf coast corrosion is a big concern so all the structural steel is hot dipped galvanized but when it has to be welded that galvanize has to be replaced cold galvanize spray paint is used. In the plants they use a brand called ZRC and I have seen it in one of our local hardware stores but it is almost twenty bucks for a spray can of it. They also have it in a version that is applied with a paint brush and with either one you have to mix it ( shake/or stir )very well to make sure the zinc mixes well with the carrier. Either way the stuff works or these industrial plants wouldn't be using it and they use a great deal of it. I'm sure sold on it.

[redbarron55]

I rebuilt the front of the frame on my 1985 16' Scamp and extended is about 18".
That helped the handling and the backing as noted above.
It also gave room for adding a heat pump mini-split etc up there.
I cleaned the rusty remaining part of the old frame and the new with Rustoleum Instant cold galvanize (epoxy). I have used it for years in industrial applications and have found it excellent. It leaves a satin finish and it does gray out with time.
It should be overcoated with a good quality top coat, polyurethane would be best, but Rustoleum black enamel is what I used where the frame was exposed to the weather.
The job is probably 5 - 6 years old now and looks very good.
A gallon of Rustoleum Instant Galvanize weighs like it is a can full of solid zinc. If you pick it up like it is a regular gallon of paint you will wrench your arm from the socket!
Expensive, but good stuff!

[Justus C]

Originally Posted by Captleemo

I have used the Rustoleum cold galvanize many times without any problems. I noticed that the instructions said to use a latex paint for top coating but I top coated mine with regular spray paint and after a number of years it has held up well although you really don't need to put anything over it. I worked in petro-chemical plants for about 30 years and spray galvanize is very widely used in every plant. On the gulf coast corrosion is a big concern so all the structural steel is hot dipped galvanized but when it has to be welded that galvanize has to be replaced cold galvanize spray paint is used. In the plants they use a brand called ZRC and I have seen it in one of our local hardware stores but it is almost twenty bucks for a spray can of it. They also have it in a version that is applied with a paint brush and with either one you have to mix it ( shake/or stir )very well to make sure the zinc mixes well with the carrier. Either way the stuff works or these industrial plants wouldn't be using it and they use a great deal of it. I'm sure sold on it.

I hadn't heard of ZRC, but it looks like a good product. Seems well-reviewed from what I am piecing together across various search hits, particularly for protecting welds. Figure a can will last me many years as infrequently as I'll need it. A bit pricier than Rustoleum but against the overall cost of a trailer, a drop in the bucket.

Once the welds are covered I'll prime the whole tongue and topcoat with enamel.

[Captleemo]

If you plan on keeping it many years you might be better off getting a can of the brush on ZRC so you wouldn't have to worry about the nozzle clogging or the propellant leaking out. And with the cans you have to do some serious stirring to blend the zinc with the paint if it has been sitting awhile. I think ZRC has a higher concentration of zinc than other brands so that is why it costs more.

[rpassmore]

You can get a POR-15 kit which includes the prep materials, about $20 on Amazon. I think it’s a 4 oz can. Not the most efficient way to buy it, but more than enough to paint the tongue. And no worries about wasting the test because the lid dried on.

[k0wtz]

I see signs of black splatter in the back of my trailer. I suppose the p/o did some work in the past. I am going the disposable paintbrush route. less messy for me.

thanks

bob

Originally Posted by Captleemo

If you plan on keeping it many years you might be better off getting a can of the brush on ZRC so you wouldn't have to worry about the nozzle clogging or the propellant leaking out. And with the cans you have to do some serious stirring to blend the zinc with the paint if it has been sitting awhile. I think ZRC has a higher concentration of zinc than other brands so that is why it costs more.