Blackened Stainless Steel

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Author Message Gary Barnett Member Username: gary_barnett Post Number: 3 Registered: 08-2011 Posted on Thursday, June 20, 2019 - 07:20 pm:    I have a client who wants to use blackened stainless steel lawn headers to separate different landscape items; for example decomposed granite from washed gravel or grass. I am concerned about the longevity of the "blackened" finish. Does anyone have any experience on the expected life of the finish in an exterior application? This project is in Northern CA. Lynn Javoroski FCSI CCS LEED® AP SCIP Affiliate Senior Member Username: lynn_javoroski Post Number: 2190 Registered: 07-2002 Posted on Thursday, June 20, 2019 - 07:37 pm:    It's been quite a few years, so this information may not be current, and it was an interior application for blackened steel. But, all those caveats aside, the consensus among the blackened steel experts I contacted was "don't do it". The color can't be guaranteed to be consistent or to last. They suggested coating the steel instead. Dan Helphrey Senior Member Username: dbhelphrey Post Number: 22 Registered: 12-2018 Posted on Thursday, June 20, 2019 - 07:48 pm:    I'd also be concerned about the chemicals used for the blackening leaching into the soil - no idea if they'd be harmful or not, but would definitely want to know before proceeding. Nathan Woods, CSI, CCCA, LEED AP Senior Member Username: nwoods Post Number: 773 Registered: 08-2005 Posted on Thursday, June 20, 2019 - 08:10 pm:    Could the designers be thinking of Cor-10 steel? Greta Eckhardt Senior Member Username: gretaeckhardt Post Number: 95 Registered: 08-2013 Posted on Thursday, June 20, 2019 - 09:15 pm:    We recently had a very interesting presentation in our office from someone at Rimex, a company that produces a wide range of stainless steel surface treatments. I suggest you contact that company. James Sandoz, AIA, CSI, CCS, CCCA Senior Member Username: jsandoz Post Number: 269 Registered: 06-2005 Posted on Friday, June 21, 2019 - 08:38 am:    For once I may have some useful information on a topic. Last October I had a similar request on a project. My research come up with the following: There are basically three ways to “blacken” stainless steel. One involves caustic solutions such as sodium hydroxide and nitrates in a high temperature bath (~300 deg. F) which convert the surface to magnetite. This process is similar to "bluing" steel as with gun barrels. A second is similar but the conversion method is performed at a lower temperature (220-245 deg. F) which is below the boiling point of the solution and gives off less toxic fumes. There is a third process which is applied at room temperature. It is not an oxide conversion but is the deposition of a copper selenium-compound. Copper selenide is itself toxic https://www.guidechem.com/msds/20405-64-5.html and must be handled carefully. Further, and as might be expected, the more environmentally friendly the process is the less durable the finish. Guest (Unregistered Guest) Unregistered guest Posted on Thursday, June 20, 2019 - 07:59 pm:    A number of companies produce colored stainless steel sheet for exterior applications. Two I've specified products from in the past are Rigidized and Rimex. More could be found here: http://www.4specs.com/s/05/05-7010.html I don't know how their finishes would hold up for a lawn header application though. I'm assuming surface abrasion from the decomposed granite or gravel would be an issue. Jerome J. Lazar, CCS, CSI Senior Member Username: lazarcitec Post Number: 2027 Registered: 05-2003 Posted on Friday, June 21, 2019 - 11:49 am:    "For once I may have some useful information on a topic"...I disagree James, I typically read your posts each time, perhaps it is because you were a friend of the late Ralph Liebing (both a mentor and an adversary). Keep posting. James Sandoz, AIA, CSI, CCS, CCCA Senior Member Username: jsandoz Post Number: 271 Registered: 06-2005 Posted on Monday, June 24, 2019 - 08:48 am:    Jerome, I hope you mean that I do occasionally have useful information to share. :-) Yes, Ralph was an amazing gentleman and it is to my great advantage and pleasure to have known him. Lynn Javoroski FCSI CCS LEED® AP SCIP Affiliate Senior Member Username: lynn_javoroski Post Number: 2191 Registered: 07-2002 Posted on Monday, June 24, 2019 - 09:02 am:    Agreed, Ralph was a good friend and it was my privilege to have also called him friend and mentor. (and, James, you DO have useful information to share - occasionally - grin)