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So I'm sure any of you out there who do metal work for a living have been asked about "Clear Coat" for metal work and keeping that natural looking finish on metal. All of us have our secrets and tricks and preferences. I recently had an outdoor fireplace screen project where the client would not budge on having it a natural forged steel look.  I told them it will eventually start rusting unless your willing to commit to maintaining the piece on a regular basis. After quite a bit of research I decided to try clear powder coating. This particular process is done without sandblasting so you do not lose the forged finish and texture on your iron work. The whole piece was cleaned thoroughly then wire wheeled, then wiped down with denatured alcohol and then one more quick pass with steel wool to take off any additional rust spots starting. The piece is then powder coated clear. This is the first time I have tried this particular process and was hoping someone out there has tried it before. Any information on clear powder coating and its longevity??

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Powder coating is a great finish until it becomes nicked chipped, or scratched. This lets moisture in and under the power coating and starts rust and the power coating starts to pop off. The only way to repair it is to remove ALL the old power coating (usually sandblasting) and apply a new finish.

Clear paint if nicked, chipped or scratched can be spot cleaned and repainted.

Look around at some of the power coating (clear or otherwise) and see the coating bubbled from moisture.

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Lots of steel bicycles out there that are powder coated.  They get lots of nicks but I have never seen one with the powder coating popping off.

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My experience was with a professional powder coater. He would sandblast your product, spray the power coating dust on it, then bake it to cure the coating. Like anything there is good and bad. I had enough problems that I went to other products for coating and protection in the outdoors environments.

 

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My experience with powder coating has been good once I found the right crowd!  Also bear in mind that there are dozens of products and textures. Also some are uv resistant and some not if you want good adhesion you have to sandblast No Question!  My product of choice is Interpol D . 

My most aggressive aplication was on the beach(beach umbrella stands in 3Cr12) on beach sand at the One And Only Royal Mirage Jumera Dubai.5years and still OK:)

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In such a situation I would forge it from stainless and charge accordingly!

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Well I considered that but isn't there treatment needed to be done on stainless after forging to keep the rust prevention?? 

 

Thanks for for the advice. The powder coater said he could not guarantee the work as he normally does since it is not being sandblasted. It's a technique he has been working on. I live in San Diego and there is a large restaraunt and brewery industry here and almost all of them have the same style. That rustic barnwood and salvaged materials look mixed with bare metal finishes. To me it's just a fad and I'm not a huge fan but, whoever is paying the bill is going to be making that decision on the finish. All I can do is stear them in the best direction and hope for the best.

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1 hour ago, Bmallen77 said:

Well I considered that but isn't there treatment needed to be done on stainless after forging to keep the rust prevention?? 

 

Passivation is the term you are looking for there. It's a chemical process. 

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I've had unpassivated forged work that hasn't rusted yet; though it's only been in use about 30 years so far...Location will make a big difference and passivation can be done with citric acid---check the canning section of your local food store as a source...

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Ok great I appreciate the info I will have to start some experimentation. I think 30 years pretty much proves it haha.

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No; I had a college friend who could etch his fingerprint on a cafeteria spoon overnight.  Environment, use, *people* make a big difference.  Personally I like the forged look on stainless and try not to remove it mechanically or chemically,  My little 440C self hilted eating knife goes through the dishwasher on a regular basis with no change.

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On ‎5‎/‎17‎/‎2016 at 6:19 AM, ThomasPowers said:

In such a situation I would forge it from stainless and charge accordingly!

3cr12 is just such an animal. Yet even 316 will rust/corrode on the beach. Anyhow it wasn't the "look" the client wanted so forge then pickle and pasivate then sandblast then powerboat matt black then technique with baroque art paste then clear powder coat over that. Yes I charged accordingly. 

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Out here on Beach Road I have to agree with Glen.

Powder coat is a great indoor finish if you have climate controll year round.

Never seen a worse case of overhyped garbage in my life.

For an excellent durable clear coat consider Sculpt Nouveau 2 part solvent urethane resin. Works great on stainless.

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Door handles will generally self polish with use, hinges may need some help.  Do a set in stainless and start testing them!  May turn out that they will degrade with time but the time exceeds the lifespan of the maker and the owner.

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I used an Isocyanate based lacquer over shot-blast and wire-brush burnished forged mild steel for the Treasury gates in Saint Paul's Cathedral in 1981. The hard gloss was cut down with Scotchbrite and wax. You could not see the plasticky coating then. 

I took them out and made a different top hinge system when the crypt area was refurbished 30 years later, and the gates went back in with just another coat of Renaissance wax. In an interior setting, with an even temperature it had stood up well.

As far as your outdoor fireplace screen project goes I would not go any where near a lacquer finish of any description. You are asking too much of any plastic to stand up to the hot and cold of fire side temperatures, UV and varying humidity.

If you forge it from Stainless Steel and passivate it you can always dull it down with a graphite rich wax...try black shoe polish as a starter if you cannot get hold of a grate black equivalent like Zeebrite. Burnish the highlights to bring out the forged texture and then a coat of Renaissance wax. This is readily renewable and will grow old gracefully between rewaxes, without the severe contrast between good lacquer and the areas where the lacquer integrity has failed through expansion and contraction or abrasion allowing ingress of moisture...applying the wax with Scotchbrite will take off any rust stains that appear.

With outdoor weather and intense heat...the less "finish" you have the better.

Alternatively sell them on a rust patination and use Cor-ten...

Alan

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Note that you could heat colour them after passivation to darken them as well; you can use the temper colours without messing up the passivation I believe but keep below forging temps please.

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So now I think maybe my best bet is to try the fireplace screen out of stainless I have never done any forging of stainless before or have I done this passivation technique. Anyone know a good video or website showing how to do the process?

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2 hours ago, Scrambler82 said:

Every piece of S/S I have ever forged rusted !

Maybe it is the type of S/S, maybe the heat level used, but it all rusted.

Why not just make it from mild steel, get it sandblasted and sprayed with a high heat etching primer and a good top cost of high heat paint ?

Etching Primer...  Needs to be Pro Grade, gun sprayed, the Rattle Cans are ok but the Pro Based stuff is far better.

Curious, I have not had that problem when I have done the appropriate finishing. What finishing treatment after forging did you give the stainless that rusted? Had you taken any steps to prevent or remove contamination of the surface? Passivation, Electropolishing?

The high heat etch primer and paint finish might cope with the fire temperatures, but you have UV and atmospheric conditions to cope with in this instance...notwithstanding that the reason for the OP's question was that the client did not want a painted finish...

Alan

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6 hours ago, Scrambler82 said:

My problem with S/S  was probably finishing, I wasn't good at it or no finishing.

The paint was more like a question, didn't notice the customers request... but a good UV clear coat would work too.

 

You seem to be going round in circles! 

As far as I know the best clear coats available, as mentioned above, are the two pack polyurethanes which contain Isocyanates...as used on metallic finished vehicles...definitely weather and UV proof for 15 years or more.

This is only part of the issue...it is for a fire screen... do you really want to be hanging by the fire while the screen is giving off toxic fumes "A range of airborne thermal degradation chemicals may be emitted during combustion of polyurethane products. These chemicals may include carbon dioxide, carbon monoxide, nitrogen oxides, hydrogen cyanide, isocyanates, isocyanic acid, amines, hydrocarbons, and other potentially hazardous decomposition products." ?

https://polyurethane.americanchemistry.com/resources-and-document-library/6936.pdf

As with any fireside furniture, the least "finish" the better as I said above...Stainless Steel and wax answer both the clients aesthetic requirement and the longevity and safety aspects.

The suitability for the end product is one thing...I also hate using toxic finishes that require full air-fed breathing and other PPE apparatus to apply.

Alan

p.s. going back to the OP's powder coat issue, I am not in the least surprised the powder coater would not guarantee it. Like any finish the resilience and longevity has to start with a good key to the substrate. Wire brushing and a wipe with thinners is not a good enough key for any paint let alone powder coat. All you are attaching the coating to is the mill scale that did not come off whilst wire brushing...time, and a few cycles of hot and cold and more of that mill scale will be coming loose along with the powder coat adhesion...

Wax has the track record albeit with a simple maintenance programme...look up Stillingfleet door....

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Stainless wise- what would you say is the best for forging and finish? By that I mean a good series of stainless. (303,304,etc..) I know you hear a lot about electrolysis mixing metals. Would I be stupid to try to incorporate copper rivets into a stainless fire screen? I know that look is beautiful but being an outdoor application am I just setting a client up for failure which in turn has my name behind it?

I did a little more research and passivation and to me, it seems like it is just essentially another coating that goes over the stainless as if it were dipped in galvanizing or plating or something like that. You think the constant heat from the fireplace will eventually burn off that coating or do I have it all wrong?

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You have it all wrong; it's much more like depletion gilding---you are *REMOVING* alloy components from the surface that rust leaving the surface enriched in alloy components that don't.  If your fireplace is burning off chromium it is probably getting close or over melting temp of the steel and you will need to go to tungsten or other higher temp alloy/metal.

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I only buy 316 Stainless Steel. I cannot tell the difference looking at it on the rack so I decided I would only have the highest spec variety in the forge...then I could not make a mistake and put bit of lower quality material into a job. An Englishman working in Germany had a horror story of one piece of a sculpted eagle going rusty on him...he reckoned the supplier had sent the wrong spec, but the wealthy patron was not happy and did not commission him again.

You need to research a bit more...passivation uses acid to remove the free iron molecules on the surface. Contamination from iron occurs in many ways...these can be as a result of careless handling/racking on a steel frame or bench. Iron transferred from the hammer, anvil or power hammer pallets, bending forks and horns, spatter from grinding mild steel nearby, use of a grinding or sanding disc that you have used on mild steel...you name it...

If you want to restore the stainless properties you must remove this contamination after forging and forming.

http://www.anopol.co.uk/passivating/

Anopol is the company I use for all my architectural Stainless treatment. There is a lot of information on their website.

The second part of the process which will give you a mirror finish on every nuance of the forged surface is Electro-Polishing. This works on a molecular level and removes all the peaks of the surface, leaving it so microscopically smooth it does not readily hold dirt and is very easy to keep clean.I love the glitter of mirror finish stainless in contrast to forged and painted mid steel. They work really well together. 

Regarding your wish to use copper rivets copper and stainless are not too far away on the galvanic table...but to be safe it is not too difficult to insulate one from another with nylon sleeves and washers.

http://www.corrosion-doctors.org/Definitions/galvanic-series.htm

Alan

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On 19 May 2016 at 0:45 PM, Scrambler82 said:

I am just saying based on my experiences, may not have many of them but then again…   life is short !

 

Life will be even shorter if you breathe in overheated polyurethane fumes.... 

On 19 May 2016 at 5:38 AM, Scrambler82 said:

Snip

but a good UV clear coat would work too.

Let alone recommending others to.

On 18 May 2016 at 10:59 PM, Scrambler82 said:

Every piece of S/S I have ever forged rusted !

Maybe it is the type of S/S, maybe the heat level used, but it all rusted.

You do realise now I hope, that it was not the actual stainless steel that rusted, but the contamination your tooling and handling process applied to it?

Based on your own research of course, rather than just some comments by an unknown bloke on an internet forum...

Alan

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Ooh this gets to be a heated/strained discourse quite quickly:D my home in Durban has electro polished 316 balustrades on the front balcony the house is supposedly  within the 100 meter/ yard line of the surf at high tide it needs to be polished every few weeks to prevent "Furring" not rust as in brown scale but pale gray oxidization.

This was certainly not my first s/s rodeo  and at a not inconsiderable expense I took every precaution to do it right.

Since learned.... 316 great acid resistance ...salt not as good so I've tried a 200 series especially imported from Sweden for some floor drains when I've recovered i'l post my findings.

S/s can be most interesting and Alan forges beautiful stuff from it :)

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