corten color

[Roy Tamboli]

Anyone with interesting corten finishing techniques?

[jwebb]

No, I don't. I thought the thing about corten was that it oxidizes to that beautiful matte rusty appearance, then stops, so that the oxidation forms a protective layer, needing no paint, etc. I suppose there must be chemical treatments (mild acids?) that could accelerate that process, but I really have no experience with it. I do have an additional question, though, in case somebody with real knowledge (Scultor Sam??) would answer it: What kind of weld rod do you use for corten, in order to maintain that uniformity of finish and color?

[fritchie]

I purposely avoided replying to the first post, hoping someone with firsthand experience would do so, but let me add my 2 cents now. I was talking to a young sculptor about a year ago, when the subject of Corten came up in some context or other. He expressed almost contempt for the material, citing the “termination” of aging generally described. He said it was now general opinion that the material just continues to rust indefinitely. He also said no one uses it today.

This view may depend on location. Here in Louisiana, where I heard that comment, the climate is quite wet and very changeable. Acids in the air (sulfur, nitrogen) from oil and refinery activity locally also may be a factor.

[Araich]

I've heard tales of Clement Meadmore sculptures falling apart at points, with chronic rust. How much this is to do with the weld material I don't know.

Dramatic changes in temperature - like shade to full sun, and damp etc will make a big difference in corrosion. Along with how close you are to the coast and the humidity.

As for finishes, the only thing I have seen is dilute acid washed over sandblasted surface.

Special cor-ten weld rod, or mig wire is used.

If you wanted a patina, I would try burning oil over the surface, phosphoric acid, water and waxes. Just a guess.

[sculptorsam]

I've also heard reports of sculptures falling apart but it was atributed more to an improper welding rod/wire than the material itself. Seems many sculptors used Corten but the same rod/wire as for mild steel so the welds continued to deteriorate. This is all hearsay on my part though.

For those interested, I contacted the engineers at Lincoln welding (isn't the internet great?!) a while back and learned the proper wire to use for weathering steel is Lincolnweld LA-75. It comes in either 30 lb. readi-reels or 60 lb. spools in either .035 or .045 dia.

I don't know of any patinas that can be applied but it is true that the location of the piece makes a difference. Here in MN, the air is so clean they take forever to rust (up to a couple years) and maintain a very even tobacco brown. The pieces I've had on the East Coast rust much quicker and take on an almost purple/blue shimmer. Very beautiful but probably more damaging to the metal.

I usually sandblast the piece and accelerate the rust with rock salt dissolved in water. Spray the salt water on the piece, wait for it to dry, and then repeat. I can condense about a year's worth of MN rust into a couple days this way. It is very important to make sure no water pools/collects on any part of the sculpture. There must be proper drainage/ventilation. I have seen the steel damaged by extensive time periods spent under water. This is why I would never make a fountain out of Cor-ten. I have a video of Albert Paley working on his sculpture for Baush and Lomb and he talks about designing the work to shed water as well as creating a hollow center column for water to pass through and air to circulate poperly.

On a side note: I'd say it's true there are fewer people using Corten than in the past. But I would attribute this more to the changing art world than any properties inherent in the steel. The material itself can be difficult to get, costs several times more than mild steel, requires special wire many places will have to order, along with shop space and equipment. It's much easier to use plaster, wood or some combination of assemblage. But I think the extra work/expense will pay off in the long run with a more resiliant sculptural object.

This is getting quite long so I'll cut this off. If you have any other questions, I'll answer them as best as I can.

Sam

[fritchie]

Araich - We’ve had a Clement Meadmore here in New Orleans, adjacent to a Federal Courthouse, for about 30 years now, but it’s a dark black color. I looked closely when it was installed, but I no longer remember whether the surface is paint or what. Probably paint. And, also, I don’t know if this was his choice in general back then, his response to local climate, or federal specification.

And sculptorsam, sorry I forgot when composing my earlier reply, that that is a favorite material of yours. Your pieces are very beautiful both in conception and in material. Interesting to hear about your experience with weathering under varying conditions, though.

[Araich]

Thanks for the info Sam. I had heard of salf but had long forgotten it. Do you do your own sandblasting (or is that shotblasting nowdays)?

[sculptorsam]

I don't do the sandblasting myself. It is incredibly cheap to have someone else do it and frankly, it is not a job I think I'd enjoy.

Thanks for the review, fritchie! I do enjoy making works with an element of beauty to them. I think it contrasts nicely with a material many see as cold/industrial. I was paid a high compliment recently by a fellow sculptor who commented that I managed to make Corten look, "more like velvet instead of just a pile of rusted metal." I liked that.

One of the most important things to remember with Corten is that it is virtually impossible to disinguish from mild steel in it's pre-rust form. I don't allow any mild steel in my shop at all so there is no confusion. It would be terrible to put a lot of time and care into a piece only to discover a couple months down the line that part of it is "rotten" so to speak.

Sam

[sculptorsam]

Forgot to mention a good site for info on the qualities of Corten and metal forging in general:

http://www.artmetal.com/

Check out the discussion section in particular. You may have to dig a bit for what you're looking for, but odds are it's there.

Sam

[Roy Tamboli]

jwebb-
I have had good results welding corten using 8018 electrodes, finishing and color.