How long will it last???

[drillmastertommy]

I am looking into a sculpture project right now that ideally would see me layering up a frame constructed from 10-12mm mild steel square bar with panels of 1.5mm sheet mild steel.

What I am trying to establish is how long the whole piece would/could potentially last outside in our nice damp British climate. A rusted finish is required and there will be lots of gaps in the plates on the frame but none big enough to get into and seal out from.

Anybody got any ideas on this?

[Ian]

It's a bit of a 'how longs a piece of string question' mate but if you've already got a rust finish on it then that rust will act as some protection from further rusting. You might look into painting it with a 'rust' coloured finish. (red oxide base for instance with a speckling of a few different brighter reds and oranges).
If you put a gun to my head I'd say a year at least, but it might last two or three or even more.
Experimentation's the only way to get a definate answer but I doubt your client will want to wait till you've found out for sure :D

[Charlotte]

A lot depends on how the piece is mounted. The kind of exposure it gets and the degree to which the site drains after a rain.

In turn there are a lot of different "rush finishes" and several variations on "Corten" type steels.

I have seen some locations in which Corten has been vary satisfactory for highway over passes while just a few miles down the road it has to be painted because of excessive corrosion. Is it going into a private home or a public space?

My personal choice would be a quick rust browning with a ferric chloride + copper sulfate+ smidge of nitric acid. Various combinations of those chemicals were used in the 19th century to produce a rust brown finish on pattern welded shotgun barrels. After several coatings the steel gets a very tight adhearing coating of brown iron oxide. This inturn makes an excellent base for clear coating. By hard wire brushing you can manipulate the finish to produce the color and texture of of the finish to produce a number of effects. It has to be clear coated with something like automotive clear coat in several layers after being neutralized.

I would use rivets where ever possible. Electric arc welding creates active sites in the metal that encourage rusting. I would get the manufacturers recommendation if using Corten type materials and follow them exactly.

Finally I would use industrial epoxy grout to anchor the statue in an effort to insulate the statue from stray electro chemical corrosion.

After all that, and if nobody messes with it 40 or 50 yeas is not out of the question with minimal care. I would have to have any stray biological deposits removed.

[Charlotte]

One other thing. I'm assuming that the frame work and the "skin" are carefully designed to minimize any crevices that might collect particulate matter or hold water.

So there you are 2-50 years depending...

I have some hr 1/4 round that has been laying on some bricks underneath a fig tree, an inch from the soil, for ten years in southern Louisiana that is still in reasonably good condition. My local climate verges on the tropical to subtropical.

(When I need new material I can buy it. I can not buy that texture.
one pass through the fire, some wire brushing some shaping and its ready for finishing.)

[HWooldridge]

Temperature extremes, continual damp and ground contact will all work against you. I have an old barrel smoker with walls that are about 1.5mm thick and it rusted out with only occasional use within 6-7 years. Of course, it was exposed to heat and the trace elements from wood smoke - but I also painted it black in the beginning so it did not start life as bare metal. In addition, I've salvaged a few steel items that laid in the dirt around our house for several years and they are about gone.

If it were me, I'd let it rust evenly so there is no unprotected steel and then apply a good quality paste wax since that will have a tendency to shed moisture. If's it's off the ground and not under cover of shade, it will be able to dry out quickly and should last many years.

[drillmastertommy]

Thanks for the info everybody, getting involved with this one does sound like it could be a bit of a lottery.

Unfortunately the design incorporates all of the elements that will work against it, i.e lots of crevices to catch and build up detritus, an inability to get inside and apply any sort of coating once finished (without dipping that is) and potentially being installed in an estate in the UK.

Perhaps I could push for an industrial galvanised finish instead, although dipping something the size of a heavy horse would be something in itself.

[Charlotte]

You could go for Corten type steel but i don't know if it is available in the sizes you need. Part of what makes it is its heat treatment. If the material is available in the size you need then follow the manufacture's recomendations to the letter and hope for the best.

[Bob JS]

I wouldn't worry ... if its going in an estate, it wont be there long enough to rust :)

[Bentiron1946]

Go with the Corten steel. It is one of the best for sculpture.:cool:

[drillmastertommy]

We are hoping for country estate as opposed to council estate but a paying customer is a paying customer!

We shall have a look into the corten steel details though and thankyou all again for your info.

[james gonzalez]

Bear in mind, Corten or otherwise, the piece will bleed iron oxide. If this were going in the middle of a paved town square or concrete slab, the eventual results would likely be unsightly.
I have experience with clear powdercoating over a rust patina on Corten. Do not do this. The surface will fail. You would be better off coating it with a product like Permalac or perhaps Penetrol, spray applied, if possible. I still suspect the piece would bleed some.