Chemists/metallurgists: help me make my rust patina stick!

Long Tom · Apr 15, 2014

I'm on my third batch of beer tap handles for a local brewery. I do a rust patina on the shaft part, which is a standard steel DOM tubing, rinse carefully, dry, then clearcoat the heck out of them. Prior to all that I clean all the oils off the shafts with a mineral spirit bath and scrub. I'm using a patina formula I got here:

1 part salt
2 parts hydrogen peroxide
8 parts vinegar

It causes beautiful rust no problem. I can even get a very course, corroded look with several applications. The problem is, it will (mostly) wash right off very easily with water! I mean right down to bare shiny metal again.

The last batch I did, I made the mistake of trying to use that really corroded patina; I eventually got it to stick "good enough" that it didn't slough off under running water (mostly). I clearcoated it, but then a few weeks later, it started to flake off. I had to scrape them all down and re-clearcoat them. A real pain.

So right now I've got 20 shafts sitting out there looking like some pirate artifact from the deep sea! But if I even look at them funny, it will come off (mostly) leaving bare metal.

Any suggestions as to how to get it to stick better? Obviously, I'm getting some sort of a scale happening, with a boundary between the scale and the remaining metal. Baking soda? Spray with plain water? I tried heat... haven't tried cold. More time? Help!

jrmach · Apr 15, 2014

Muratic Acid ?????????

Chip Chester · Apr 15, 2014

Follow up with clear heat-shrink tubing? Or a thick, built-up coating of whatever they use to make bar tables look "dipped in plastic".

Any chance the bartenders are polishing up those old rusty tap handles?

Chip

Sea Farmer · Apr 16, 2014

I make display stands for antique nautical things and old tools. One customer likes an "antique" patina. So I just leave a bunch of HR outdoors for a year or two, laying on the ground. It comes out pitted and with a deep patina.. Wire brush the loose stuff off, chuck the pieces in the tumbler--the patina is deep, and remains along with the texture. I do a bit of grinding to get to clean metal on the weld lines. Any kind of oil or clear coat preserves it.

Not to my taste, but the customer is always right, and she makes a lot more money designing than I do making the stuff. And there's not much labor involved while the stuff is just laying there.

course, you probably don't have a year or two. . . . :scratchchin:

Long Tom · Apr 16, 2014

No, I don't, and I've done this twice now with eventual success. It's just driving me nuts that it can get SO rusted, but it's not "grabbing" the surface of the metal. Also driving me nucking futz that I have so little understanding & control of the process.

I'll take a pic tomorrow. When y'all see it, you won't believe that it'd just wash off to bare, bright metal! Mostly. And that's weird too.

rcoope · Apr 16, 2014

A great friend of mine is an machinist and artist who's ardent desire in life is to live in a kind of very carefully designed simulacrum of an abandoned factory. This is a problem as his wife tends more towards the "folk chickens" aesthetic. Nevertheless he's done an amazing job with the back yard where has made artful use of muriatic acid. He has a piece of schedule 40 4" pipe cut lengthwise as a gutter on an outbuilding which is actually almost too rusty after the muriatic treatment and being outside for a couple of years. Likewise the 2" downspout and some custom mount fittings but I don't know if this because of the head start of the muriatic acid because it's steel of dubious origin, but it's several different pieces of steel and they're all surprisingly rusty. Having said that his BBQ which was wonderfully adapted from a ratchet forge and which is kept out of the rain seems to have a perfect patina which with not clear coat has stayed stable through a couple of years.

Akzle · Apr 16, 2014

dont know if it will work as intended, but, reverse electrolosys? Same solution, but with parts clipped to the red one and some shitty d16 rebar for black. Shitty d16 rebar should be easy to come by.
Gently does it.

Akzle · Apr 16, 2014

if what you call 'mineral spirit' is what i call 'turpentine', wrong cleaning fluid - Will leave residue on surface.
Try methylated spirits (purple, dont know what youd call it) or ethanol.

markaj · Apr 16, 2014

If you can get it in the States (& I'm sure you can) you should try some stuff called Jade Oil by Liberon. Just wipe a thin coating over your rust/patina finish & then a couple of coats of wax or a lacquer on top. It is good stuff, and is actually a kind of micro resin. It works well on ally & brass to keep an 'off the machine' finish without resorting to lacquer.
The problem with things like beer taps is that the coating will inevitably wear through, so maybe a hefty coat of 2 pack over the Jade oil.
As to getting the rust in the first place, I can't help you there as I spend my life trying to keep it at bay! In my neck of the woods, just leave it outside for a week.....

Butcher · Apr 16, 2014

Drop your parts in clorox bleach, that will rust in minuets.

ECJ · Apr 16, 2014

We do a lot of hand done, cold worked patinas in the shop and while it is definitely an art, there are many commercially available products that do a great job, and with which we have personally had good success. Try Vista Patinas http://www.sculptnouveau.com/cw3/assets/product_expanded/tbr00008z.jpg, or Birchwood Casey. You can get a variety of deep browns and even mottled old looking finishes. We seal with exterior grade lacquer, typically Permalac, and the finishes hold up well.

ECJ

medic0079 · Apr 16, 2014

you can put the part in a salt water bath and run a current from the bath to the part. pos wraped around the part - to the bath.

Lakeside53 · Apr 16, 2014

Here' you often see architects specifying the "rusted" surface coated with Pentrol (paint additive for flow control). Look great, and lasts outside.

Thomas Paine · Apr 16, 2014

the problem is not your method, it's the crappy steel. I assume 1020/1026 ??? It will just crumble into nothing and flake off no matter what. Try a structural steel variant, w/ copper in it, they are made to rust and hold their form, for outdoor applications.

example: COR-TEN

starbolin · Apr 16, 2014

Wrong material. Like Tomas says. Grain structure too small - too much chromium - too much aluminum ( AK steels ) - not enough carbon - whatever. Ever notice how an old high carbon chisel or hammer you can polish all day long and it still has a brown patina. Old rifle barrels too.

Also, flash rust will just wipe right off. You need a deep pitting but not all steels pit the same way. Some will start at a small spot and just pit all the way through, some will change to darker colors and some seem to just rust so far and stop. I never stopped to figure out which is which. ( Some AK steels will rust but then nothing in the world will stick to them afterwords. ) The proper treatment to color each will be different.

It would be a good idea if, in the future, you tested a small sample of your steel before you machined it. Polish a small slug, heat it to a straw color, and quench it in peanut oil. You want a steel that gives a nice brown finish. If the oxides scale off or turn black this may not be the steel you are looking for.

Heat would be my preferred method of coloring steel. More controllable, less messy.

Long Tom · Apr 16, 2014

Interesting. Thanks.

As to type of steel, I'm limited to stuff I can get in a thin-wall DOM tubing for relatively cheap. This last batch of tubing I got is .049" wall thickness which is GREAT. I have to keep the weight to as light as possible.

This is a picture of the last batch of these I did. This is the rough patina that did "grab" the metal, eventually, well enough to not just wash right off. However this ended up flaking off in spots after the clearcoat, which might also have been due to not rinsing the salt & vinegar etc off well enough prior to coating.

Those had thicker-wall tubing, in the realm of .069" if memory serves. So again, I'm somewhat at the mercy of what my local steel yard can find for me. This last batch, the .049" stuff, they located and ordered in. I had to buy all of it. So I've got enough for my NEXT batch of these handles on hand already! Gotta make this stuff work.

I was attracted to this patina fluid because of it's non-toxic nature and because I felt like I could stop the reaction with a good rinse when it got where I wanted it. And because I can make it in my kitchen.

Maybe I need to branch out to get something working with this particular batch of steel.

I'll go out and take a picture of the stuff that's rusting right now. You won't believe that this will just wash right off to bare metal.

What I was HOPING is that some whiz chemist would say, oh, you've got too much oxidant and blah blah blah. Reduce the amount of hydrogen peroxide blah blah blah.

bic · Apr 16, 2014

Just send them to my brother.

Every time he borrows tools from me they always come back rusty...

bhigdog · Apr 16, 2014

You might try bead blasting to clean the steel and give it some tooth to hold both rust and clear coat......................Bob

Long Tom · Apr 16, 2014

Here's a pic of the "crusty rustys" and one that I just rinsed. Crazy!

Long Tom · Apr 16, 2014

Butcher said:
Drop your parts in clorox bleach, that will rust in minuets.

Immersed? Or is air contact afterward needed?

The inside of the tubes is a precision surface; needs to NOT rust...

Chemists/metallurgists: help me make my rust patina stick!

Stainless

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Aluminum

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Plastic

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