Should interior of hollow steel outdoor sculpture be coated?

[Harry McDaniel]

While there are numerous threads regarding paint/coating/finish options for the exposed surfaces of outdoor steel sculptures, I haven't found any mention of treatment of the interior of hollow steel outdoor sculptures. I am curious what other sculptors are doing. Of course, water will condense from the air and run down the interior walls, causing rust if the steel is untreated. Is it such a small amount of rust that it is not worth worrying about? Are finishes worth the trouble of applying in awkward places? Is it best to just use thick sheet metal and forget it?

[copperhead]

Rust is going to get anywhere and everywhere it can. I have made a couple of large-ish scaled outdoor mild steel pieces, and I use the same clear coat on the inside as i do on the outside. While thick sheet metal may last longer, the rust is going to get it too. I have found that it is better to really try to do a thorough clear coat or paint job, because anywhere you miss is going to rust out. Also, I have found that as far as nooks and crannies that are hard to reach with a brush or airgun, it is a lot harder to reach them with a cup brush to remove rust.

[warren01]

Harry, like you said condensation and you will have moisture and then rust. Almost impossible to make air tight. In fact I have found I have less rust if I make it to have more ventilation and a drainage system. Not only rust problems but around where I am from we also have damage from ice build up.
If possible look into having the piece dipped, galvanized, or metalized. I am not sure of the process but there are a couple sculptors on this site that uses the metalized method. I have been thinking about doing this with a couple of future pieces, but still only in the thought steps.
Of course these pieces are usually painted.

There was mention of the metalized process in this post. Maybe somebody can give a little more information because I would also like some more information.
http://www.sculpture.net/community/showthread.php?t=1161

warren

[bobcoon]

Hi Harry, Although I have not found a really good method for interior coating, I have seen outdoor steel sculptures literally fall apart after a few years. The corrossive nature of our environment, in Florida on the ocean, is one of the worst. I am sure it would take less time for the same thing to happen elsewhere, but I am also sure it will happen. This particular piece was well made and well finished (on the outside) it was air-tight enough that larger volumes expanded and contracted with heating and cooling. It was junked!!!!!!! Will powder coating be attracted to the interior?
Please share you findings, and good luck.

[fused]

I don't think there is any practical way to apply a protective coating of any kind to the interior of a steel form. Platers and galvanizers (hot dip) will not treat a closed form, it has to have a large opening before they will allow it to be immersed in their tanks.

Thicker material in your forms is one answer. I have oxidized mild steel sculptures that have been outdoors for 25 years and are still holding up fine,these include cylinder shapes capped on both ends with 3/8" plate. The surface is treated with WD-40 (http://www.wd40.com/) which I buy in gallons and apply liberally with a spray bottle in the summer when the steel is hot from the sun.

Steel contains iron --which I have been told has a natural tendency to draw oxygen from it's surrounding environment-- and is porous enough to absorb moisture. When my acetylene torch heats my steel welding table it sweats so I figure something is going on there. My thoughts on this finish --which may be a total misconception-- is that the summer heat drives moisture out of the rusted steel when it's too hot to touch and that the WD-40 penetrates the surface and helps seal moisture out. In adverse conditions this process is repeated twice a year and none of my steel surfaces scale or anything once the color is uniformly dark. I have a friend --John (http://www.texassculpturegarden.org/content-artists.asp?artist=1021) Brough (http://muarchives.missouri.edu/c-rg6-s36.html) Miller (http://www.valleyhouse.com/index.asp?main=thumbnails.asp?mode=artist&artistid=125&srcpage=10)-- who works almost exclusively with enclosed mild steel volumes and uses this same finish, but he doesn't weld any material less than 1/2 inch thick (12.7mm). John's welded joints are huge to insure that any corrosion will take many many years to ever become a problem.

I've heard of people drilling weep holes and such at the bottom of closed forms to eliminate the accumulation of moisture
but I've never worried about it enough to do that.