Weather proofing outdoor ironwork

[Harris Snyder]

Hi guys,

 

Out of curiosity, how do smiths weatherproof outdoor pieces like gates, fences, driveway chains, etc? What way works the best in the experience of those of you here?

[SoCal Dave]

It all depends on maintenance issues.  Nothing is forever outdoors and it depends on your location... Alaska vs Arizona?  I use automobile clear coating to protect the metal, but even that will need maintenance at some point.  Primer, paint, and clear coating works if the customer wants that type of finish.  A wax type of layer will work for a short period, but will need to be reapplied.     

[Harris Snyder]

Well the particular installation I'm thinking about will be in New Hampshire... Maintenance would be acceptable every 3+ years, but the longer the better. Would stainless steel treated with a black patina solution (they are available even for stainless) be a better bet than just coating mild steel?

[John B]

Stainless is expensive and difficult to work, Galvanising or hot zinc spraying will give 10years plus protection.

Ordinary paint finishes also work, the key is in their preperation, bare metal, degreased, primed, then undercoat and topcaot. Then pay attention to any problem areas and treat them if and when they arise. And put in place a maintenence plan

[Alan Evans]

Stainless steel electro polished is the best maintenance free. It looks like chome plating almost...it is chrome oxide. Getting anything to key onto a stainless steel surface is problematic, the clue is in the name. The only black surface treatment I could find was Peoton and that was small items they could treat in an enclosed atmosphere as part of a production run. Rod ends for racing cars was their speciality I seem to remember.

Do tell about the patina solution system you have found. Is it self do-able? It sounds to good to be true.

Shot blast, zinc spray, etch prime, under coat and top coat(s) or hot dip galvanised, etch prime, under coat and top coat(s) will get you up to 25 years maintenance free in an "inland polluted atmosphere", less on the coast. I have been quoted those specs by my finishers in the past.

I find that making architectural forged work out of stainless steel should be priced at about four times that of mild steel, although the finishing by electro polishing is cheaper than paint or powder coat on top of zinc on mild steel.

I have done a couple of jobs and am currently working on the third where I have been able to persuade the client to accept an as-forged stainless surface. These are handrails forged to and octagon section and have the loose oxide stainless wire brushed and Scotch-Brited away with a pneumatic drum sander and then a periodic coat of renaissance wax. The client knows that the surface may get the occasional rust colour from the contamination of the steel hammer pallets and forming tools. The patina that builds up from the wax and use is to my eye the best.

Alan

[lupiphile]

                                 I've blackened quite a few large (8x15-20 ft....or 2438.4 x 4572-6096 mm) ss, architectural panels at the old fabricator's shop I worked for  It was the middle of winter and the cold patination process is extraordinarly temperature sensitive, but given the size of the pieces I'd say its a process well adapted to doing it yourself. The only prep was a throrough  bead blasting. And very carefull handling  afterwards as the oils in your hands would create a mottling of the finish where it had been touched. it makes for a very pretty purple/black surface that I think would lend itself quite well to regular forgework. In the instance  of my smaller experiments i'd say getting the stainless acid dipped first,to remove scale, would help the patination take and keep from getting furry. As to availability on the otherside of the pond, I haven't the foggiest idea, The stuff we used was a harbison-walker product ordered from a place called Chem city,If I recall correctly it was a nickle,silver,and stainless blackener,  maybe they have a european distributor? The serious downside, like with all chemical patination,  is how incredibly toxic that stuff is. Just looking at the bottle it comes in is enough to send my kidneys running for cover.The fumes aren't that bad  but all of the nasties are absorbed readily through the skin ( like you get some on your hand and you taste it in the back of your throat 3 min. later) So thats something to consider. But it looks nice and holds up for just about ever, So that has to be worth some more minor form of cancer, right? Plus you' all have national healthcare in place......Over here I only know of about two professional blacksmith's with a real health insurance plan. My policy reads about like " if your arm is severed off, this policy and 5000$ will get it reattched"

 

                 As to the abatement of that flash rusting that occurs on stainless when its been worked with steel. I've had great success with either dipping it or giving the work a light wash in a dilute phosphoric acid, it gets into all the nooks and cranies and converts any latent rust, to phosphoric oxide( nice neutral black) that is more or less permanent. Hope this helps,Take Care, Matt 

[Alan Evans]

                 As to the abatement of that flash rusting that occurs on stainless when its been worked with steel. I've had great success with either dipping it or giving the work a light wash in a dilute phosphoric acid, it gets into all the nooks and cranies and converts any latent rust, to phosphoric oxide( nice neutral black) that is more or less permanent. Hope this helps,Take Care, Matt 

 

Matt, Excellent information, thank you. Makes good sense.  

 

My stainless spoons and bottle opener size bits I bead blast or wire brush after I pickle in a phosph(e)ric acid  barrel but that has got a bit contaminated with copper and other stuff over the years.

 

We used to use phosphoric acid based gunk on old car repairs, that was Jenolite (or Genolite). I have just picked up some mordant solution to etch/darken a galvanised project which I think is phosphoric acid based. But I will certainly explore further and get some to use that technique on this job. Thank you again.

 

I will bear that terrifying Harbison-Walker blackening system in mind for the future, maybe I can find someone that is geared up safety wise who will do it for me! This project will look best with semi burnished highlights I am happy to say.

 

Alan

Edited May 20, 2013 by Alan Evans

[Harris Snyder]

Very interesting... I might be looking into that stuff as well.. It does sound egregiously toxic, so break out the hazmat I guess (joking).

[Alan Evans]

I suppose your phosphoric dip must do what the nitric acid does when they passivate stainless. I have had it back after passivation looking flat and almost white and have then bead blast and / or burnished and waxed it. But when left from the hammer and burnished it has a much more articulate patina it looks "live". If I do it myself in the phosphoric I should be able to get it somewhere in between the two!

Alan