Speeding up the oxidation of COR-TEN
Speeding up the oxidation of COR-TEN
(OP)
Dear all,
Can anyone provide any info or resources on sucessful methods to speed up the natural ~ 3yr. oxidation time for COR-TEN steel to a matter of days? I have heard that although, generally, pretreating is not recommended it can be done. Has anyone had success doing this without doing more long term harm than good from an aesthetic or performance standpoint? If so, what patinating agent and application method would be appropriate. Any assitance would be greatly appreciated.
Can anyone provide any info or resources on sucessful methods to speed up the natural ~ 3yr. oxidation time for COR-TEN steel to a matter of days? I have heard that although, generally, pretreating is not recommended it can be done. Has anyone had success doing this without doing more long term harm than good from an aesthetic or performance standpoint? If so, what patinating agent and application method would be appropriate. Any assitance would be greatly appreciated.





RE: Speeding up the oxidation of COR-TEN
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A couple of years ago he was working on something to allow weathering steel to form its patina despite being immersed in water, or something like that.
Why do you need this?
Hg
Eng-Tips policies: FAQ731-376
RE: Speeding up the oxidation of COR-TEN
Dik
RE: Speeding up the oxidation of COR-TEN
oxide coating on?
RE: Speeding up the oxidation of COR-TEN
RE: Speeding up the oxidation of COR-TEN
I done a lot of work on the steam/air oxidation to force an oxide coating on carbon steels when we were evaluating anodes. I've been scanning my notes to see if Corten was looked at.
RE: Speeding up the oxidation of COR-TEN
But other mills make weathering steel (ASTM A 588 et al).
Hg
Eng-Tips policies: FAQ731-376
RE: Speeding up the oxidation of COR-TEN
If the part is immersible in a tank, perhaps a reverse galvanic cell could be used to acellerate the formation of a patina.
RE: Speeding up the oxidation of COR-TEN
Aside from the process mentioned above we used several methods and all involved Chlorides.
One was to expose the component to HCl vapors at ambient temperature.
Use a saturated solution of NaCl and spray on the part let sit for several days and rinse off. Repeat.
Use an acidified solution of NaCl about 1% HCl by volume to the saturated solution.
We also used an acidified solution using Acetic Acid and
NaCl.
RE: Speeding up the oxidation of COR-TEN
RE: Speeding up the oxidation of COR-TEN
RE: Speeding up the oxidation of COR-TEN
It turns out that plain CS was the better anode material.
RE: Speeding up the oxidation of COR-TEN
Hg
Eng-Tips policies: FAQ731-376
RE: Speeding up the oxidation of COR-TEN
RE: Speeding up the oxidation of COR-TEN
TXDoT did the same thing with a number of HSLA steel fabricated bridge beams around town and failed to paint them, the rust streaks look like crap too. All for want of a few hundred gallons of paint.....
If an architect or civil engineer ever tells you he doesn't need to paint because the patina will protect it from corrosion, just shoot him and get it over with. He may be right, the patina will prevent corrosion but the stain will never look good.
RE: Speeding up the oxidation of COR-TEN
TxDOT has since done quite a few weathering steel bridges that are designed not to drool rainwater down the concrete supports, and they look fine years later. In Houston they did all the detailing and also painted the ends just to be sure, but the color match is awful. In Austin they didn't do any of that and they're fine.
Paint would still be required near expansion joints in areas where road salt is used, to protect the steel from such an aggressive corrosion environment (and in such cases I'd probably advise painting the whole fascia surface to avoid the color match problems), but the key to avoiding the ugly staining is in the detailing--drip bars, weepholes, drains in the columns, etc.
There are a number of guides out there for detailing weathering steel to avoid staining. I don't really know how well any of that would work for a building. (If anyone has any building references I would be quite interested.)
Hg
Eng-Tips policies: FAQ731-376
RE: Speeding up the oxidation of COR-TEN
Yes we have completed testing a new Active Coating for Protective Patina Formation on Weathering steels in 1-2 years exposure. Corrosion decreases X10 in zero-to-very high chlorine environments, and all wetness. No bleeding. Can be colored or natural patina color. Search PatinaForma for details and my contact info.