adding a patina or other finish to hot rolled steel

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Hi again,I built a large sign for a client that would like to find some way to give it a "gun black" type of finish.  I have never applied a finish to metal before beyond standard enamel paint.  I researched patina's and found that they require that the mill scale be removed so that the color or stain can soak into the metal.In addition it turns out that mill scale can be detrimental when left and painted over as it does not protect the steel and when moisture gets under the scale, the metal will rust and the paint will still be in place over it.That aside, is there a way to give hot rolled steel a black patina that can be burnished with a scotchbrite pad or similar material?  Can anything be applied to give a black finish to this project without removing the mill scale.  If I have to remove the scale, how is this done on such a large piece?  It stands 8 foot high and wide.Attached is a picture of the project in question.Thanks,Tony Attached ImagesLast edited by therrera; 04-05-2013 at 02:20 PM.Reason: To add a few more photos
Reply:I messed around with some scrap by heating it up with my little MAPP gas torch and then cooling in motor oil. Got everything from deep blue/purple color to almost black depending on how hot it got. Using that method may be difficult on a large irregular shape piece like yours though if your looking for a uniform and even color/ finish.
Reply:Look at Sculptnouveau.com They have lots of patinas, and are very helpful if you call them. I have had good luck weith their products.  Gun Blueing is called PC9 on their website. They also have some pretty good clear coats.I have no affliation with them. www.scultpnouveau.comCool sculpture by the way.Last edited by mnt; 04-05-2013 at 05:21 PM.Reason: forgot to say cool scuplture
Reply:Easiest thing would have been to ask the question before construction began, as using P&O or cold rolled works better because there is no mill scale. Garden sprayer with muriatic acid will, with some time and effort remove the mill scale. Sand blasting will do it as well. There are some sculpt Nouveau products that will work, though you will need to topcoat with their clear coat as well. Nice work so far, though finish is the hardest part.
Reply:Sandblast, PC-9 + gloss or satin clear powdercoat. You can get the PC-9 at Ball Consulting in Tempe or at Industrial Metal Supply. Arizona Powder coat is great quality and cheap. Just takes some time to get through their lead time. I just clear coated some hot roll .120 plate with a mix of Japanese brown and PC-9. Looks great but not what your client is looking for.
Reply:Heat up the entire sign but not cherry red.  Once hot, throw down used motor oil on it.
Reply:Originally Posted by MoonshineMetalsHeat up the entire sign but not cherry red.  Once hot, throw down used motor oil on it.
Reply:It really depends on the "type" of patina you are looking for...if you want weathered paint .... then paint with different colors of paint, nothing bright,you need to take your time and let each layer dry for a decent amount of time, then use 600-1000g or so wet sanding paper and sand back through the layers in different areas. I would stick with enamels for this... Or use lemon juice or other light acids to make it rust then polish out the rust with steel wool...  Any type "blueing" will need to be kept oiled or even clear coated but even then it will still eventually be degraded by the sun/rain... getting realistic patina will be a project in itself.Lincoln pro mig 180Lincoln Square Wave Tig 300/wp 20/home built water cooler Victor, Purox, Harris, O/A welding/cutting setupsVintage Craftsman drill pressVintage Craftsman/Atlas 12"x 36'' lathe7''x 12'' w/c band saw Everlast 140 st
Reply:Thank you all for the tips and suggestions.  I finally settled on a black metal wax.  I was able to give the piece almost two coats with a pair of 4 oz. jars of the stuff.  I go tit from Industrial Metal Supply.The reason I chose it is because it could go right over the mill scale and gave the piece a dark luster almost as if I had sprayed on a clear coat.  It gave a look of polished steel not unlike what a gun might have or smooth oiled machinery.  The stuff dries to a real hard coating which protects the metal in addition to looking nice.I had thought it would give a blacker tone but I was not disappointed with the results.  It was also a good experience in giving metal a finish other than paint.This shot doesn't capture it well, but the wax highlighted the "rivets" and gave a luster to the metal.Thanks again,Tony Attached Images
Reply:Nice finish, Tony. What did you use for the 'rivets' if I may ask? I do like the way they stand out.PapaLincoln Idealarc 250 (circa 1962)Lincoln Weldpak 155 w/Mig KitLincoln Squarewave TIG 175
Reply:Hi Papaharley03,I used some semi-spheres available at many ornamental iron supply shops.  They come in all sizes starting at around 1" and go up to like 12".  I attached a close  up of one for your to check out.The only thing I didn't like in the piece I made was that I needed to put two tacks to hold them in place which was visible.  In this case it was not too bad as the piece will go on a wall above people so close scrutiny will not be possible.The only other way to have attached them was to punch (drill or plasma) a hole through the metal and tack to the edge of it from the inside.  This however would have added a lot of man hours to the project (to to mention precise measuring) so I went the cheaper route.The client wanted an "industrial", machinery look to the piece.  I did a quick search of the type of place that carries these and came up with this:http://www.decorativeiron.com/produc...category_id=31Thanks,Tony Attached Images
Reply:Not doing a lot of ornamental stuff, I didn't know these existed. Very cool! I'm wondering how much amperage it would take to resistance weld them to the sign. Since they're not solid half spheres, maybe not so much. Just a thought.PapaLincoln Idealarc 250 (circa 1962)Lincoln Weldpak 155 w/Mig KitLincoln Squarewave TIG 175
Reply:Hello fellas and lurking ladies,   Thanks for the compliments.I am relatively new to ornamental stuff as my main bread and butter is in the repair welding side of things.  Also I fabricate and do custom welding but it is pretty straight forward, off the shelf stuff like lengthening a trailer or building a truck rack, etc.When I lived in Chicago 30 years ago I used to build a lot of iron fences and gates but they were plain types totally functional with very little ornamentation to them.  Very spartan looking when compared to high end ornamental iron.This particular client is bringing me jobs that are having me spill into the artistic realm so its new territory for me.  I am having to explore the HOW to achieve a particular look or to fabricate a particular item (like a 5 foot skull he had me build a couple of months ago).http://weldingweb.com/vbb/showthread.php?t=251591Now he's talking about building a 23 foot mermaid????  So its interesting to say the least and I like learning new stuff so it comes at a good time for me.Thanks again,Tony
Reply:I use a schit load of hemi's/sphere's in my work. On my mirror frames I tack a 1/4 bolt to the inside of the hemi and it sticks through a 1/4" hole in the mirror frame and get's bolted on. A mod on this method when you don't need to have the hemi's removable is to weld a stub of 1/4 round rod into the back of the hemi. Drill a 3/8" hole in your flat base and weld the 1/4" into this 3/8" hole. Grind flush. I love the piece, but the visible tack's kinda killed it for me. But, if the client is happy, then that's all that matters. Another good "rivet" source is carriage bolts. Though would be harder to find big enough and more $ than the hemi's for this scale project. I do like the mill scale finish. Nice variations in color. 200amp Air Liquide MIG, Hypertherm Plasma, Harris torches, Optrel helmet, Makita angle grinders, Pre-China Delta chop saw and belt sander, Miller leathers, shop made jigs etc, North- welders backpack.
Reply:Yeah Bert I also didn't like the surface tacks.  I asked the client about it before doing it this way and he opted for the quick route as he did not want to invest more money into it than necessary.Since it was going to be hung up high, the tacks would not detract from the piece.  I found out he got a lot of compliments on it so it must have worked out as he had hoped for.The method you proposed for avoiding the tacks sounds good.  In this case it would have added a days more work but if the finish required it, so be it.Thanks for the ideas,Tony
Reply:Yep! Happy client is a returning client. And working to their budget is part of it. Love to see pic's of it installed if you have any. 200amp Air Liquide MIG, Hypertherm Plasma, Harris torches, Optrel helmet, Makita angle grinders, Pre-China Delta chop saw and belt sander, Miller leathers, shop made jigs etc, North- welders backpack.
Reply:I'll see if I can get some pics.  This sign is destined for a Chicago location. Ironically I will be going there in a few weeks.  I think I'll ask my client which club its going to and I might be there when its installed and can take pictures.We'll see.Tony
Reply:Tony, do you remember the exact name of the product you used? I'm dealing w a similar situation myself and found this thread. Also, does the product darken the ground down welds at all? I have one long bead that is ground and the client doesn't really wanna see it. Thanks! Also, great job on the sign!
Reply:A thought about attaching the rivets  drill 1/8" or 3/16" holes the diameter of the rivet then plug weld them   gxnxc