What's a good weldable anti-rust coating for mild steel?

martin_05 · Jul 15, 2021

I am looking for a way to protect mild steel from rust post fabrication. This could be weldments or machined parts. Whatever the method it needs to be weldable. In other words, a machined part gets coated and put away and later pulled off the shelf to go into a weldment without having to grind anything off.

Someone mentioned something called "AF400". All I can find is a polyurethane coating by DuPont. Not sure that would be compatible with welding.

I also spoke to an applications engineer at ITW. Their "Rustlick B" product is fully weldable and will protect from rust for about three weeks. They suggested their LPS1 product could also be used for this purpose and offer longer term protection.

ITWProBrands

ITWProBrands

mhajicek · Jul 15, 2021

Crown Tool and Die Saver. Sprays on like an oil, dries like a wax. Easy to clean off, probably wouldn't have to clean before welding.

Gordon Heaton · Jul 15, 2021

How about stuff like anti-spatter spray and nozzle gel. I think the gels are wax based, and un-heated after application they seem to last a long time. Just a thought.

Cole2534 · Jul 15, 2021

I believe the spray paint STEEL-IT is weldable.

Sent via CNC 88HS

D Nelson · Jul 15, 2021

Body shops use a weld thru primer on body panels. Check that direction
Don

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D Nelson · Jul 15, 2021

Sem 39783 weld thru primer
Don

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martin_05 · Jul 15, 2021

D Nelson said:
Sem 39783 weld thru primer
Don

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Thanks! I research the weld-through primer next.

I believer I may have found the solution I was told about. If so, they had the part number wrong. SP-400 by CRC is a corrosion inhibitor with a two year protection specification.

SP-400™ Corrosion Inhibitor, 5 Gal

I'll call the company tomorrow to ask about welding. My primary concern is that the coating should not turn into something that could send you to the hospital under the heat of welding. While the MSDS says it's flammable, I am going to guess this is the case for the liquid form. My guess/hope is that it isn't the case once applied and dry. Clearly this stuff can't be anywhere close to the welding area in liquid form.

What would be appealing to a solution like this is the potential to just be able to dip parts in bulk as opposed to having to spray paint every surface and orifice by hand.

The other thought I had was vacuum-packing. This would be far more labor intensive than dip-coating in bulk. The advantage might be that you are not dealing with dangerous chemicals.

Hillside Fab · Jul 15, 2021

I use Slide mold shield or no-rust depending on how long it will sit, but clean it off with acetone before welding.

My guess is all of the good inhibitors are a version of petroleum wax with stuff in them to neutralize any salts and acids.

I'm guessing the primer paint mentioned would be OK with MIG or Stick, but I wouldnt want it on anything I was going to tig weld or need to have porosity free.

plastikdreams · Jul 15, 2021

Hillside Fab said:
I use Slide mold shield or no-rust depending on how long it will sit, but clean it off with acetone before welding.

My guess is all of the good inhibitors are a version of petroleum wax with stuff in them to neutralize any salts and acids.

I'm guessing the primer paint mentioned would be OK with MIG or Stick, but I wouldnt want it on anything I was going to tig weld or need to have porosity free.

+1 for slide, top of the line products.

Hillside Fab · Jul 15, 2021

Cole2534 said:
I believe the spray paint STEEL-IT is weldable.

Sent via CNC 88HS

6010 will weld thru almost anything, although you might need a respirator

Scruffy887 · Jul 15, 2021

Boeshield? At The Rust Store. No idea if weldable but I use it a lot.
Boeshield T-9, 12 oz. Aerosol

metalmagpie · Jul 15, 2021

My suggestion is to use brake cleaner. :-)

martin_05 · Jul 15, 2021

The idea is to use something that doesn't turn toxic when welding.

To be fair, wearing a respirator for prolonged welding is a good idea regardless.

martin_05 · Jul 15, 2021

D Nelson said:
Sem 39783 weld thru primer

I was just looking at this. That part number was discontinued but it looks like there's a replacement (#40773.

What stopped me on my tracks is that the formulation is zinc based. The reason welding galvanized steel is a bad idea is that the zinc coating will vaporize and the zinc oxide fumes are not good for you. So...how is this zinc-based formula not just as bad?

I need to call them and ask that question.

Mud · Jul 15, 2021

martin_05 said:
Thanks! I research the weld-through primer next.

I believer I may have found the solution I was told about. If so, they had the part number wrong. SP-400 by CRC is a corrosion inhibitor with a two year protection specification.

SP-400™ Corrosion Inhibitor, 5 Gal

Ask also about SP-250. SP-400 is thick like cosmolene and dark in color. SP-250 is water thin, and dries to an almost unnoticeable waxy layer. supposedly you can paint over it in some circumstances so I'd think you could MIG through it with little notice. I've used SP-250 and really like it. It keeps bare steel rust free indefinitely indoors. I have samples of SP-400 but never wanted to apply it to anything so far.

Garwood · Jul 15, 2021

EG is made to be welded. Most parts in EG are welded. No coatings required.

tylersteez · Jul 16, 2021

I've used weld thru primer before on autobody repairs, however I dont trust it at all when it comes to the "primer" part. I just see it as added protection in a lap joint. If I was to paint the part I would certainly take the weldable primer off first

crossthread · Jul 16, 2021

My shop does not have conditioned air and it gets pretty swampy here in Virginia. I have been fighting rust for fifty years or so and have come up with only one solution that is truly cost effective. The military knew some stuff about rust prevention but I don't have access to cosmoline. I do however have a lot of beeswax since I raise bees. Even if you don't raise bees the stuff is pretty cheap (some beekeepers I know give it away). Beeswax dissolves in pretty much any organic solvent (Turpentine, mineral Spirits,ether,acetone, xylol, benzene, chloroform etc.). I dissolve about a cup of wax in a gallon of mineral oil and keep it in a closed metal can. Any time I need to protect something I either dip it in or brush it on. It forms a thin film that is not sticky and yes, I have welded through it many times with no problems. I have not tried tig but it sure works on stick and mig.

martin_05 · Jul 16, 2021

crossthread said:
My shop does not have conditioned air and it gets pretty swampy here in Virginia. I have been fighting rust for fifty years or so and have come up with only one solution that is truly cost effective. The military knew some stuff about rust prevention but I don't have access to cosmoline. I do however have a lot of beeswax since I raise bees. Even if you don't raise bees the stuff is pretty cheap (some beekeepers I know give it away). Beeswax dissolves in pretty much any organic solvent (Turpentine, mineral Spirits,ether,acetone, xylol, benzene, chloroform etc.). I dissolve about a cup of wax in a gallon of mineral oil and keep it in a closed metal can. Any time I need to protect something I either dip it in or brush it on. It forms a thin film that is not sticky and yes, I have welded through it many times with no problems. I have not tried tig but it sure works on stick and mig.

Wow, that's really neat. Thanks. I'll have to ping bee keepers in the area and see what I can learn.

martin_05 · Jul 16, 2021

Garwood said:
EG is made to be welded. Most parts in EG are welded. No coatings required.

Sorry, what's "EG"?

What's a good weldable anti-rust coating for mild steel?

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