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Produce a Rich Rust Patina on Iron and Steel, Safely and Quickly, Using Common Household Chemicals

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  This instructable will show you a fast, safe method, using common household chemicals that you probably already have, to produce a rich rust patina on iron and steel to give it a weathered, aged appearance.

Background

I've had this Maine 'buoy bell' wind chime for about eight years now. I really like it. It has the haunting melancholy sound of a bell buoy at sea being tossed by wind and waves. It is made of COR-TEN steel which is designed to rust on the surface to create a protective barrier against further rusting. It came painted black on the outside and was supposed to develop this rich rust patina naturally over time. Well, the unpainted inside did rust completely after about a year, but the outside only rusted slightly, near the bottom, even after exposure to the sun, rain, and snow of the northeast for eight years. I wanted it to have a nice rust patina that looked like it had been hanging on the eaves of a lobster shack, at the end of a pier, for many a year, being splashed and buffeted by nor'easters and sudden gales. Seeing it was taking so long, I decided to take things into my own hands and, ah, "help" mother nature along and accelerate the process. I searched the net and found mostly dangerous methods to induce rust on steel using highly caustic or acidic chemical solutions. However I finally did find a simple safe method, using on-hand household chemicals, buried deep within a thread on the subject at a metalworking forum. I got spectacular results which have not only withstood the wind and rain of the southwest but have actually improved with the help of mother nature. I like the results so much, and there is so little practical information on the subject that is accessible to the general public, I thought I'd share this simple method with the instructables community.

Judging by the number of posts on forums asking how to do this, I see I am not the only one who wants to actually promote, rather than prevent, rust on iron and steel objects. I found out the basic information for doing this at the very cool ArtMetal forum: http://www.artmetal.com/blog/bob_turan/2009/04/rust_promoter . I'm guessing that there are more than a few instructables members who have a similar desire to prematurely age some iron/steel artifact, so I encourage people to post pictures of their resuls in the comments and add tips on how they did it so we can all learn. This method is not set in stone. Posts about useful variations on the method are always welcome.
 
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DaveT161 month ago
Hello, the company I work for is hanging 7x5' Corten Steel panels on a 200' long wall. The patina on the steel panels is darker than we'd like. We're trying this formula to make it more orange. How long does it take after we spray it 4-7 times? Also how long do we need to wait before we seal it once we get the colour we want?
Laral (author)  DaveT161 month ago

It sounds like they already have a deep patina which you'd get after leaving them outside for a while or if the patina was created using strong acid. Did you try a patch to see if you can still create an orange patina on top of the old one? It's impossible to say how long it would take, but on bare clean metal the results are instant. It should be bone dry before sealing it. A heat gun would accelerate the drying.

DaveT16 Laral29 days ago
We came to the same conclusion about too deep of a patina after trying the solution on the back of one of the panels. Nothing really changed. I found that by wiping a dry cloth over the surface it lightened the colour a bit closer to what we are going for. Do you have any suggestions on reversing the patina to get back to more of an orange colour before we seal it?
Laral (author)  DaveT1629 days ago

Another thing I am thinking is that the sealer would also darken the color so be aware of that and maybe try it on the back first.

Laral (author)  DaveT1629 days ago

I was afraid of that. There is no way to reverse it. The only way to get what you want would be to sand off or etch off the patina to bare metal and start over. If the patina is very shallow you could sand it off but it would be messy and a lot of work. You'd be best to take them down and work on them in a safe place. It is possible that sanding would rough up the patina and actually give you a lighter color. That would be easiest.

I had laser cut mild steel letters
and logos for a customers building. We did a muriatic and hydrogen
peroxide patina and the letters came out beautiful. I sent them out to
clear powder coat and the guys had ruined them. I had the powder coat
baked off and the metal sandblasted. We are trying to re-patina the
metal and it is just not biting into the metal at all. I have
re-sandblasted the metal a few times thinking maybe there was residual
powder coating somehow left behind. The only thing possibly different
now from the time we first did the set is the air temperature outside.
Is there anything we can do to get the rust to bite more into the metal
so when we neutralize it and rinse the rust does not come off the
surface? Does the air temp effect the process ( 1st time when the came
out great was upper 70's and now we are in the 100's )? Any direction
would be greatly appreciated.

Laral (author)  siccsinister1 month ago

What did the powder coat do? Why not just leave them as is and let nature take over? I see rusted iron signs all over the place and they are natural.

By bite do you mean form a deep patina or that it is not forming any patina now? If the latter, maybe the surface is too smooth. Did you try pickling it with acid again? That seems to be a necessary step. Read my section on pickling.

Higher air temp should accelerate the process. I did the bell in 100+ degrees direct sunlight.

Don't rinse it at all if you use the mild mixture that I recommended. I guess you would have to if you used muriatic acid but you say that removes the patina. So what is the advantage of using a caustic acid like that if it doesn't produce a deeper patina? Why not try this much safer mixture?

We sprayed the acid a quite a few times on the metal prior to the hydrogen peroxide. I am thinking the acid is evaporating to quickly due to the heat now and not getting a chance to work.
Laral (author)  siccsinister1 month ago

Ahhh! OK. Then why not put the letters in a plastic pail with a lid on it and just barely seal the lid to allow escaping gases. You can get 3 gal or 5 gal 'icing buckets' for free from Sam's club or any bakery.

We need to clear coat the metal because it will be attached to a new building and do not want rust streaking down the building later. We have used the acid multiple times and had success always. The first time around they came out beautiful. After tne powder coat was ruined (to much was sprayed on and left extremly milky areas) and baked off we are now strugling with the patina getting the deep various colors.
Laral (author)  siccsinister1 month ago

I was afraid of that. So now you have bare metal right? Did you try just acid to pickle it before using acid/peroxide mixture?

Robellido2 months ago

You think if if pour iron oxide on top of the clear coat on the hood of my car I would get this nice effect without it rusting??

Laral (author)  Robellido2 months ago

I don't know. You mean a red iron oxide powder sprinkled onto wet clear coat? It would probably not look the same. It would be more uniform. Natural rust tends to have variations over the surface.

Robellido Laral2 months ago

Iron oxide that you get when rusting steel wool completely. Mmm then I guess I'll have to sprinkle it uneven cuz I don't want my hood rusting for real. It may develop holes from that or damage it badly. I'll try to do this on a sample piece of metal first to see how it looks.

Laral (author)  Robellido2 months ago

No you would not want to rust the metal itself. Try a sample piece like you said. The only thing is, it may very well wear off in time and will not look good. Then you will have to strip it and start over.

Laral (author) 3 months ago

I posted this before but there is no way to link to it so I'll just quote it:

Have a look at: https://web.archive.org/web/20080108073034/http://asuwlink.uwyo.edu/~metal/patinas.html -- the second formula. I got a sal ammoniac block from Ace at the time but I don't see it now at their website. I found that eBay has ammonium chloride powder cheaper than what I paid for the block. It would also dissolve much easier than the hard block.

Very easy to do, cheap, works great.

Here is my sample done on a copper tubing end cap.

cr.jpg
JosephB83 months ago

how do you patinate copper or brass ?

So Cal Urb made it!3 months ago
Here are my results so far... i had already stripped and sanded down this fender to bare metal... then rinsed with water, sprayed with white vinegar, then with the mix of vinegar/hydrogen peroxide /salt. .. so far i think 3 times ive done the treatment... thank you for this post - I plan on making this into a mailbox! I'll update the progress.
IMG_20150518_130429.jpgIMG_20150518_130743.jpgIMG_20150518_130901.jpg
Laral (author)  So Cal Urb 3 months ago
Well, it looks like it is rusting nicely. Please do post the final result.

Hello,
I paint signs. I have a customer who would like a rusted steel sign, and I was thinking of preserving the lettering as shiny steel while rusting the background. This means I would need to mask off the letters so the muriatic acid doesn't eat through the mask. Does anybody know what I would use to coat out or mask the letters to keep them from rusting?

I know this sounds crazy but use finger nail polish to protect the lettering then use finger nail polish remover when finished
Laral (author)  kimberley.edwards.9424 months ago

I don't know about muriatic acid. You'd need something impervious to acids, like a plastic-based paint, acrylic, epoxy, but then you need to remove the paint without damaging the rust. Difficult. I see a lot of rusted metal signs that have laser-cut lettering. That'd be the way to go.

DavidG87 months ago

Hi Laral, I recently applied your treat formula on some corten steel planters. About 12 hours after I applied the treatment, it rained non-stop for two days. The steel is orange in color and has not darkened. What do I need to do to darken it? Is there anyway to get the two planters to match quicker (doesnt have to be perfect but somewhat better than now).

BTW, I applied your treatment to the other planters about 5 months ago.

DSC_9112_01.JPG
coyles1 DavidG87 months ago

Hi David,

Note if this is made from Corten then it will stay a lot lighter then raw steel.

Corten has an Orange colour to it, as you can see in Image attached.
The fresh bit was installed today.

Kind Regards,

Rogan

10953650_1536656303252229_1443385857_n.jpg
Laral (author)  coyles17 months ago
That's really orange. What did you use to rust it?

Note that my wind bell is cor-ten but is a lot browner than this.
Laral (author)  DavidG87 months ago
Only time and the elements will darken it really. The treatment only produces thin surface rust. Those planters look like they have a nice dark patina.
LucyBW7 months ago

Hi Laral,

Thanks so much for posting this rusting process!

I’m trying it out on a steel fire pit .. as we ‘speak’…

Here’s a question: I’m looking for a way to seal the rust finish,
which won’t result in toxic fumes if it
is heated by fire.

I want the rust finish but not quite so dirty to handle. I
am not expecting to find a sealant which will hold up over time and weathering
and fire. Its ok if the sealant breaks down when it is in direct contact with
fire but I’m not ok with toxic fumes.

Any suggestions?

Lucy

Laral (author)  LucyBW7 months ago
That's a tough one. I have no knowledge of a non-toxic sealer that won't emit toxic fumes near fire. An idea would be to try using just egg yolks and water. See http://www.instructables.com/id/Egg-Tempera-Painting/?ALLSTEPS for the general idea and http://www.eggtempera.com/technical-info/egg-tempera-paint for details. "Tempera paint is insoluble to the extent of not being picked up by over painting and when completely dry is relatively water resistant. However, the paint is not absolutely water proof and can be disturbed by the application of water."
LucyBW Laral7 months ago

Wow - That's an interesting idea. I'll have to experiment a bit with this one. I want a clear sealer. It'll be interesting to see if egg yolks without pigment results in a clear coat.

Thanks for responding

Laral (author)  LucyBW7 months ago

Oh I think the thin coat will be clear, especially if you dilute it with water or vinegar. A little yellowing probably wouldn't be noticeable either.

alex.hunt.1278 months ago
Im currently building a rat rod out of my pick up, and im thinking of using this process for the body. I was curious if you think it would work well on a large surface and also if there are any concerns I should consider before proceeding. Thank you.
Laral (author)  alex.hunt.1278 months ago
I don't know for sure since I never tried this on anything that large but I don't see why not. Who would know more about that is http://www.instructables.com/member/scott.snow.921/. You could PM him. He does commercial metal work and he did mention using muriatic acid for rusting. That is more dangerous and has to be neutralized with baking soda or some base but it may be more suitable for a project like yours. You could try this method first on a small out-of-the-way area and see how it comes out. The only thing is, the rust is just on the surface in the beginning and is easily brushed off. You'd have to clear coat it to prevent that.
ehall191 year ago
Hi, I know this post is a few years old but I just found it yesterday and tried it out on my box bike frame and it worked great but the rust wipes right off. Will the rust adhere itself to the metal over time and stop doing this, or will it just stay on the surface? Hopefully I hear back from you. And thanks for this post, I used the exact same ratio you posted and it turned out great! Only prob is that at this point it wipes right off.
*bmx bike frame not box bike frame hahaha!
jcapella ehall198 months ago

hey, just thought i'd mention that this will significantly decrease the strength of your bike frame...

Laral (author)  jcapella8 months ago

I doubt it. Rust is only on the surface.

jcapella Laral8 months ago

Rust might begin at the surface, but it does weaken the structural integrity, and will deepen as you mention in this instructable. Unless his bike frame is corten steel...

Laral (author)  ehall191 year ago

If you can avoid touching it for a while, the rust will penetrate deeper and become permanent. Or you can seal it with acrylic or polyurethane spray.

ehall19 Laral1 year ago
Ok awesome! As long as it will eventually adhere to the metal that's fine. Hopefully it won't take that long. Once it does I'm gonna spray it with some matte clear coat(I hoping/assuming that's what you mean by acrylic or polyurethane spray) to seal it. I bought the frame in bare metal(no clear coat) and as soon as I got it(when it was still all nice and shiny) I put some die cut stickers on it so that once it rusted I would peal the stickers off and the logos would be "unrusted" in to the frame while the rest of the frame would have a nice rusted patina. But it was taking forever for it to rust and when it did start to rust it was really uneven. But your formula worked great!! I'd like to post a pic in this comment to show you how it turned out but can't figure out how to do it. Anyway, thanks a bunch!
Laral (author)  ehall191 year ago

It could take some time to develop a thick layer of natural rust. Wet it often and leave it in the weather. You could just clear coat it right after you rusted it but a thicker natural layer of rust would be more resistant to scratches. Please post photos, this sounds really cool. Isn't there an 'Add Images' button below the edit box? You need to enable javascript.

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