Intentional rust

I don't know about the coating, but I do know that plain salt will accelerate rusting quite a bit.

Craft stores (Michaels, etc.) sell patination chemicals. Typically people put on a sealer, then base coat of metal paint, and then apply the patina chemical.

One of the chemicals explicitly says "rust"

You can skip the first two steps. :-) But if you want to to a large area, it might be too expensive. :-)

WATER?

Thank You, Randy

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Add salt to that!

Ammonium nitrate is the best. (yes, I tried)

Kind of humorous; all the country boys slapping Koolkote on the rusty roof to make it all new and silvery looking while the city boys are spraying salt water on the roof to make it look all old and rusty :-)

Bruce-in-Bangkok (correct Address is bpaige125atgmaildotcom)

It sounds he's talking about A-606, which is basically the same thing as Cor-Ten, except that A-606 is the designation for thin sheet.

This is a self-protecting "weathering" steel. If you're lucky, and if there isn't too much pollution in your air, it rusts into a nice, even, rich brown color in a few years, something like a browned rifle barrel. If you're not lucky, it looks like a rust-streaked wreck for around a decade.

The Picasso sculpture in Chicago's Daley Plaza, made of Cor-Ten, looked like holy hell for years and years. Finally, it started to look decent. I think the problem has been attributed to air pollution.

If it were me, I'd check with someone who knows what he's talking about before trying to accelerate the rusting. My guess is that it will fail. They didn't have much luck in the early days trying to accelerate rusting of Cor-Ten, but, as with nearly everything else, I haven't kept up. d8-)

-- Ed Huntress

Yeah, that's the kind of application that Cor-Ten was made for. It came out in the late '70s, IIRC, when I was covering materials for _American Machinist_, and it was being promoted for all sorts of structural and decorative uses. Here in NJ they used it for guard rails on the lower end of the Garden State Parkway. Like most applications, it looked like hell for a few years and then it turned a nice, rich brown. It looks pretty good, and it saves a lot of maintenance cost -- which is the whole point of it.

Because the rust has to form a dense and nearly impermeable structure, it matters how the rust is formed, and I think it matters how fast it's formed. That's why I'm skeptical that you can speed up the process. But maybe they've come up with a chemical treatment for it since those days. I haven't followed it.

-- Ed Huntress

I'd spray them with soap to remove any oil, rinse and leave them out to rust by themselves. Wet oak leaves discolor steel quickly. Once they have a rust film, spray on some diluted rust inhibitor such as LPS-3 to stop pitting.

A-606 doesn't pit, Jim -- if A-606 is indeed what Steve has. It's a high-strength low-alloy (HSLA) steel that's formulated to produce a protective coating of rust that, after it penetrates to a certain depth, stops rusting. The rust forms a dense, nearly impenetrable layer.

-- Ed Huntress

The Cor-Ten tradename covers a number of weathering steels. The first, Cor-Ten A (ASTM A242), dates back to the 50's. By the time I was taking my structural courses in the early 70's Cor-Ten B (ASTM A588) had obsoleted the earlier material. It was pretty common by that time, if you knew what to look for.

There's at least one more specification for sheet -- the stuff above refers to structural shapes.

We used Cor-Ten for the traffic signal mast arm structures in our town's downtown area, but we did not leave them bare. Instead, we had them painted them a color that was near to their final natural hue. The idea was that they would never be painted again, but we would not have to concern ourselves about pitting in any of the inevitable scratches inflicted during installation, and we would not have to wait for them to age to a pleasing patina.

25+ years later, they are still doing fine.

Vaughn

The obvious answer is to set them on the ground outside wherever you and your buddies drink beer, and keep the fridge stocked.

How does that work?

As far as browning, I just re-did a barrel we clocked to get the sights pointing straight (damn thing shot way left and you know I can't tolerate that), I used some Birchwood Casey Plumb Brown.

As far as the brown goes, I thought it was combination of the rust + oil that kept it from rustiong further.

Obviously something different goes on with Core ten.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

I forget. I haven't had to know for 30 years, so I just let it run out my ears.

I love that stuff. I got really great results on an old single-barrel shotgun. It looked like a real antique when I was done.

Yeah. Different stuff. Cor-Ten does it with the alloy -- somehow.

Here's some good stuff. First, Ted Mooney is a very knowledgeable and no-b.s. guy on materials and finishing:

You'll notice that using muriatic acid to speed up the process is mentioned here.

Second, here's US Steel on the subject of using weathering steel for roofs:

-- Ed Huntress

Second

Did a large steel sign last year. A36 with raised laser cut stainless lettering. They wanted a rusty finish. Knocked off the worst of the dirt and gave it three or four "coats" of the following with a cheap spritzer bottle----- a quart of 3% hydrogen peroxide with a quarter cup of hydrochloric pool acid mixed in. Pretty amazing how fast it works.

The company I worked for, used it for pier nosings on a bridge in Jamaica around 1967.

Here in NJ they used it for guard rails on the lower end of

Gerry :-)} London, Canada

Yeah, I guess it was around a lot earlier, from what a couple of people have said. I probably was just on the receiving end of a big promotional push. US Steel was pouring on the PR for a few years, and they were sending us everywhere, from the steel mills of northern Indiana to the coal mines of southern Indiana.

-- Ed Huntress