Clear coating to seal a rust patina finish on metal

A. Hi Tommy. We'll see if Steve's e-mail address still works and if he responds. There are many brand names of clear coats, and we don't really like to focus on them ( huh? why?). Some are available in satin/matte finishes, which limits the shine, but all coatings will make the metal somewhat more shiny for the simple reason that you presently have a rough etched finish, and whatever you coat it with will be smoother and thus will not scatter the reflection as much.

Please consider Everbrite [a finishing.com supporting advertiser], which is available in matte. They have a great web page detailing the issue of protecting rusted finishes ⇨
... plus they help make this page possible :-)
Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Mr./Ms. Powell,
I tried to answer that one just above. Please visit the suggested site which goes into a lot of detail on the issue.
Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Dear Mark,

A good polyurethane should do the trick. I would usually recommend an acrylic base coat followed by a urethane. This makes the urethane much easier to strip, when it comes time to repair/maintain the patina and substrate.

adv.
Contact me if you would like more information.

Regards,

Q. I have the same interest as Ed in clear coating over a rusted surface. In my case it is for steel sculpture, as I do fairly large pieces for indoor and outdoor use. Many times I want to keep the rusty look. Any suggestions? Thanks, Ken MacDonald - N. Kingstown, Rhode Island 2004 Q. Like Ken and Ed I am interested in an exterior clear coat that will work on rusted metal. We are expanding our signage to include etched and distressed metals and need a durable clear for exterior use. Thanks, Steve Halmhofer, shop manager - REDDING, California 2004

A. I think that you can use proprietary polyurethane paint or spray. Some of them contains rust inhibitors (Krylon spray). Good luck!

A. I have been using the same approach to accelerate rust and have been experiencing the rust peel you describe. It is my belief that the acid causes the rust to happen too fast. I suggest you experiment a little with vinegar [in bulk on eBay or Amazon]. That seems to work fairly well and quickly. Also be aware that the texture is different than with the acid.

A. In Response to neutralizing.... baking soda [on eBay or Amazon] will neutralize acid. Wipe the surface with water/baking soda mix and drying it fully, quickly. it will stop the patina process.

A. Hi, Richard. I suspect the reason you couldn't find a great answer is that there may not be one :-(
It's said that a chain is only as strong as its weakest link. Here we have a link of steel (your welding bench); then a link of loose, powdery, non-adherent rust. Then a link of clear coat. And people report that as stress is put on the clear coat, the clear coat pulls off, "taking rust with it".

But I suspect that if the rust is quite thin, such that the clearcoat can "wet" it all the way through to where the clear coat can actually grab some sound steel, you may get acceptable adhesion. Good luck.

A. Automotive clearcoat. Seals the rust without inhibiting the appearance, and the thicker you lay it on, the more protected you are. If it gets severely scratched, just buff with a little clear coat polish and a buffing cloth.

A. Hi, Rose. A couple of thin coats is probably best, but you must brush any loose rust off first. A chain is as strong as it's weakest link. If the rust doesn't adhere to the substrate, it does no good to have the clearcoat adhere to the rust -- it just comes off as a package deal. Clearcoat is not shrink wrap; it has to adhere to the base steel or to rust that itself has some adhesion :-)

Regards,  

A. For my restaurant in Portland, we formed sheet steel panels to fit our back bar, laid them in the parking lot and sprayed them with muriatic acid [affil links] (diluted a lot) and salt water and let the rain finish the job. When finished it looked like marble and burled wood--nobody guessed it was rusted steel.

We burnished it with fine steel wool [affil link on Amazon] to remove any powdered rust, leaving a smooth and intact finish and polyurethaned everything. We put a few coats on, as I recall.

It was inside and not exposed, but in the 8 years I had the restaurant (before I sold it) it showed no signs of additional corrosion or breakdown of the poly finish.

Looking at clear powder coated finish for my next project.

Michael

A. Hi Marion. Let me first clarify what automotive clearcoat is, in case any readers are confused. It's a "2-component" or "two-part" or "2K" coating material. It is usually polyurethane but it hardens the way epoxy hardens -- in other words it doesn't "dry", it "cures" as the two components react with each other. You have to mix the two components in the right ratio, and must complete the project before it hardens.

There is no reason you can't brush it if you can work quick enough, or do it in several batches. Use cheap disposable brushes as there is no way to clean them. We don't like to recommend one brand over another, but I'm sure a local automotive store will have it -- just don't talk yourself into a single component clearcoat if you want "automotive clearcoat". Good luck.

Regards,

A. Hi Evenilde. Some colors are pigments, and a clearcoat won't effect them; but some "colors" (like the rainbow sheen of a drop of oil on a puddle, or from a CD/DVD, or the colors of titanium jewelry, or the changing colors of some oncoming headlights) are just diffraction effects. These effects happen because the oil, or plastic, or metal coating is transparent and so thin (partial wavelength) that light waves bouncing off the inside of the clearcoat and the outside "interfere" and cancel out some of the colors of white light, leaving only the remaining.

The bad news is that any clearcoating will always destroys these diffraction colors because the clearcoating is too thick for partial wavelength effects. I can't say for sure, but I believe this is what is happening to your "yellows" and "oranges", leaving only a brown rust color. Sorry it's not good news, but at least if you know what you're fighting you may be able to figure out what you want to do.

Regards,

A. A great clearcoat I have found for sealing this rusted effect is Motostorms Glamour clear. Its a polyurethane so more flexible than urethane clears, which has been a life saver on some of the thinner metal projects I've done. It adheres amazingly well to rust. Of course, as pointed out, the large rust flakes can be a problem. Your best bet if you want to preserve the large rust flakes, is to either, scrape them off, put a light coat of clear on, then sprinkle them back on..., or hammer the part with LOTS of clear over the course of a few days. This will form a 'bridge' of strength over the looser flakes.
The small powdery rust can be a problem. But if you can lay your project flat, using the Glamour clear or a good quality automotive clear, add some retarder to it and hammer on one or two hard coats to the project and leave it be for 24 hrs. This will saturate the rust and the slow retarder is just added insurance for more saturation. A good quality clear must be used though. So many out there are loaded with cheap flash solvents.

Yes, you can apply automotive clear with a brush. Mix small amounts at a time. Brush on one light coat, clean your brush while you wait 30 min for first coat to tack up, then repeat until you have the build you want.
You CANNOT use those foam brushes. Automotive clear will melt them. A natural hair brush should work. I'm not sure about others. Also, don't put the brush all the way into your mixed clearcoat. The clear solvents may eat any glue that is holding your bristles in. Then you will have hairs in your project. :(

Try to avoid using Baking Soda. If you MUST use baking soda to neutralize your project, neutralize the project with vinegar after the baking soda. Baking soda will keep your clear coat (or even primer) from adhering to the project at all. Later down the road, especially when exposed to the elements, your clear coat can start to turn cloudy. This is air pockets forming behind the clear as it is trying to delaminate.

What I have done for my rusted effects is hang part vertically, spray with muriatic acid. Wire brush in downward strokes. Blow dry with 100 psi air. Spray part with plain water (deionized water if your water is not neutral). Blow dry again with lots of air pressure. Then I spray it with a good quality solvent based wax and grease remover. Then blow dry again. At this point I like to let it sit in the hot sun for about 30 min while I mix up my clear. I then bring it in, let it get down close to room temp, and hammer with Glamour Clear with a few drops of retarder added. I let sit over night. Then I sand it with 320p Grit paper, and then apply a few more coats of clear until I get the smooth finish I want.

Ed. note: Please see letter 17478 for a beautiful rust-finished table & an incredible pencil sketch on rusted steel, and letter 16945 for a hot woman made of cold steel.

A. KBS RustSeal clear, neutralizes as well .

----
Ed. note: We're not sure if David is precisely right because we've found that product in lots of colors, but not "Clear". We have, however, found "KBS DiamondClear" and are not sure if it's really the same stuff as "KBS RustSeal"

A. Hi, Charlene

It's risky to guess what a 3rd party meant without hearing their actual words, but I'll guess. Some clear coats are single component, but some, like epoxies and automotive clear coats, are two component. You can't use just one part of the two part system: epoxy for example will never dry, but will just remain a sticky syrup unless mixed with the required catalyst or "hardener". I guessing that you went to buy a clear coat system and tried to buy just one component of the two-component system. Good luck.

Regards,

A. Hello again Charlene

Okay, I'm finally catching on. The "automotive clear coats" that people are talking about are not coatings like Krylon where a solvent evaporates and allows them to dry. Rather they are two-component coatings like epoxy where mixing two components causes a chemical reaction that makes the mixture harden, as opposed to drying. You don't sell the two components in a single can because it would quickly be just a solid hard mass rather than a liquid. The way it is done is the automotive painter takes a can of component A and a can of component B, mixes them together, then rather quickly pours the mixture into his spray equipment such that they are sprayed on within a very limited time after mixing them.

Adding to the confusion, people sometimes call component A "clear coat" and component B "hardener", although component A by itself is not really a useable clear coat, just a sticky syrup. So buy the can labelled "clear coat" (component A) as you were doing, but also buy the hardener (component B).

If you don't have professional spraying equipment, you can't spray two-component automotive clear coat*.

However, you may be able to successfully brush it on after mixing the two components. Although I have no experience in that, Adam B. describes it above. This may be what your friend is doing. Use a very cheap brush and a cheap mixing cup because once the mixture starts hardening, they become garbage -- there is no washing them. And practice on a piece of your scrapped art; don't go directly to an important piece.

Regards,

A. I've been force rusting steel projects for many years and have found a successful process. I wash the steel object with water and dish soap and then spray it with a vinegar and salt solution. This step accelerates the oxidation process.

Once the piece has rusted to the correct patina I wash it in a warm water and baking soda [on eBay or Amazon] solution. This step stops the accelerated oxidation. Note, it only stops the accelerated oxidation.

Next I burnish the piece by rubbing it with an old leather welding glove that smooths the rusted surface and adds yet another interest dimension to the patina.

Lastly I coat the piece with clear coat. My best results have come from a matte finish polyurethane, but have also used an automotive clear coating system as well. I usually use several thin coats. This final step seals the surface and essentially stops the oxidation process. The oxygen can no longer cause any problems.

I haven't had problems with my pieces chipping clear coat or peeling rust. I think the key is a light coating of rust, neutralizing the forced oxidation, and completely sealing the surface.

A. Hi, Peter. If you have the ability to mix and spray, I think a 2-component automotive clearcoat might be best. They are relatively thin and durable, and they are probably pretty readily available around the world. But it sounds like Tom D of Minnesota has good advice born of actual experience.

Regards,