Protection for outdoor steel sculpture

A. Dear T.W

From your question I understand that you are in the US. It is not obvious that you want to protect clean steel or rusted steel. Rusted steel cannot be protected; you have to remove the rust by acidic paste (ask your local chemical finishing supplier or in DIY shops). In case you want to protect the steel and improve adhesion of the lacquer you have to accomplish process called anhydrous phosphating. Henkel Surface Technology has product called KEPHOS 253 which is preparation of steel or brass before paint for increasing paint adhesion and corrosion resistant under paint or lacquer. This layer is obligatory before paint and it is transparent layer. Yours,

A. To your problem with the piece that you are mounting up high like that you may wish to use a Polane A for metals... We use this regularly on all types of metals from steel to copper etc. Often it is used to seal pieces that we have added age to with rust and the Polane works best and seals very very well. Sherwin Williams carries it and it is expensive and requires a three part mix. Do several heavy coats and allow them to dry and cure each time. The time lost will prove to be worthwhile as you will find that it will work well.

A. Dear R.H.

The most successful rust patinations I have found come from applying muriatic acid ⇦this on eBay or Amazon [affil links] . It is made for concrete purposes and can be bought for a cheap price. After the application, apply boiled linseed oil ⇦this on eBay or Amazon [affil links] or a paste wax. I think you'll be pleased w/ the array of browns, reds, and oranges.

A. Perhaps Cor-ten steel would solve your problem. As I understand it, Cor-ten develops a rust on the surface, but that oxidation doesn't go any deeper.

A. Hello all, Colin here ... first post!
Interesting comments. That is also my understanding with Corten steel, also called rusting steel. I think shipping containers are made from it.
I have made a variety of outdoor pieces in cast and forged steel/stainless steel, cast bronze, etc. and currently having a few issues with a silicon bronze plaque that needs to remain bright to distinguish some relief etched detail. So far I've tried a patina or two, Renaissance Wax ⇦this on eBay or Amazon [affil links] , and now a clear coat called Icralac ⇦this on eBay or Amazon [affil links] from a can (made for copper and brasses). We'll see?
I've since found there are good products on the market that are used for marine applications, i.e., aluminium boat hulls. The one I will try next is called Magnum by Altex coatings here in NZ. Having a chat with the tech, it sounds like it is so far good for 6 years in testing -- dulling but impervious.

Cheers
Colin

A. Regarding Corten steel, it does hold up better than other rusted steels, but some sculptors have found that it still continues to degrade over extended time.

Regarding bolting bronze to steel, you will have an increase in corrosion much like the problems they encountered with the Statue of Liberty where copper plates were bolted to iron brackets. You need to somehow insulate the the two or use stainless steel, but then you will not have rust as a patina.

We've used Incralac ⇦this on eBay or Amazon [affil links] on our bronzes as far back as the 1980's, but were dissatisfied with it's lack of staying power. For about 20 years now we have been using Permalac [adv: Permalac on eBay] made by Peacock Labs. it is a synthetic lacquer made specially for copper alloys (and it works great on many other surfaces as well). Outdoors it seems to last for a good ten years or more depending on conditions and is easy to re-coat.

A. Hi Jaydeep. That's a very impressive artwork :-)

Obviously, if it could be displayed indoors, clear coating should be quite acceptable. If it must be outdoors and you must retain the metallic look, your only choice is a good clearcoat, which has been previously discussed on this thread -- but I feel this might be trouble-prone or require maintenance. Some areas look so hard to reach that you might investigate whether clear e-coating is available as a primer coat because it will give complete coverage.

If it can have a painted finish it's possible to do a much better job, with zinc phosphate, followed by electrocoating, followed by powder coating or spray paint which should last a couple of decades.

Regards,

A. Try SST Perma-Protector. That is special nanotechnology-based coating (sst-oberflaechentechnik.de/en/Products/). Very expensive and very durable (up to 20 years of protection). Hope it helps and good luck!