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deviljohn 02-21-2010 08:54 AM

Metal Finishing Questions....
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I am working on a project for an architect constructed of 10 ga sheet..the piece will be outside in the humid climate of the coastal south...initially, the client wanted to paint the metal, but I think the piece will look better w/ a natural metal finish look..wondering what's out there to seal and best preserve the metal.

Also, what's the best way to remove the black mill scale finish on the sheet metal??? Sand it off?? Thanks, here's some pix..basically it's a birdcage mounted on a treated lumber table w/ 3 low voltage lights inside..whacky yard art, but a paying gig..

randydupree 02-21-2010 09:11 AM

let it rust.
The mill scale needs to be blasted off,and hatever you seal it with will come off one day,so just let it brown out by itself..

Ironman 02-21-2010 09:41 AM

There are steel types which wil rust to different shades and colors, used for modern "art"
I would use cold rolled sheeting and then you don't have to deal with the mill scale, but if you let it rust , the scale will rust off too.
You can clean off mill scale with hydrochloric acid also.

I sometimes finish with cleaning with acid, this will cause a light rust if not washed right away, after cleaning with acid, give it 2-3 days for rust to form, and then spray with automotuive clearcoat. It won't last any longer than the paint on your car...

It comes out a warm red-brown coulor

OLD MAN 02-21-2010 09:47 AM

First off, welcome to the forum.

Your craftsmanship shows and you have done a fine job.

The treated wood will need an annual application of Thompsons Water Seal.

I agree with randy and would clean it and apply Ospho and start the rust and clean it again and then allow the natural rust to work. An annual water blasting would slow the rust to prevent deep pockets.

If a finish is what the owner wants, you need to satisfy the owner. The headquarters for Valspar is in your area and has a big research dept and a great consumer help dept. I am positive they can supply you with a two part epoxy that will meet your needs and I also think they can do it clear as well.
Go to the experts and take their advise.

The hard part will be the wire. I am afraid it will have to be replaced in an outside area in your part of the country.

Again, welcome and a very nice job.:(:(

tnmike 02-21-2010 09:50 AM

You can heat the metal and apply butchers block wax and it make a nice , natural finish. I wont , however, hold up outside long. The only thing I can think of would be some type of clear laquer but I have never tried it.

spanishgrass 02-21-2010 10:02 AM

Its a little late for this but for future reference there is a product called "Core 10". Its metal that is formulated to reach a certain point of rust then stop rusting. We installed some on the entryway to our new shop. Since we don't get that much moisture here it will take a while for it to color. We purchased it from a company that specialized in metal roofing and siding.

Walker 02-21-2010 11:28 AM

Yep, yep, yep, cold rolled to avoid the mill scale and core ten (or Corten, or core 10, I think the Core stands for corrosion, and the 10 for some alloy they put in it to keep it from rusting away). I don't think you will find much core 10 in anything but structural shapes and sheet goods and it will be special order.
So, to remove the mill scale mix up solution of 50/50 muratic (pool acid) and water. Put it in the cheapest garden sprayer you can find, the cheap ones have all plastic parts and the acid doesn't hurt them. Spray on and let sit for 20 minutes or so and then hose off, repeat as needed until the mill scale is gone. If you want it rusty then just leave outside and wt it down for a while, covering it with a wet towel works well too. You can either leave it bare, or clear coat it. I have used clear coats ranging from $100 a quart automotive clears, to PermaLaq, to rattle can clear to polyurethanes. They all have their benifits. For outside on rust I would use a outdoor polyurethane. It can be sprayed on, it is cheap ($15 Qt), self levels well, available in a satin or shiny finish, dries quick, and lasts for years. Look for those in the hardware store, sometimes called spar varnish, but make sure it is urethane spar varnish. When it is damaged it can be sprayed on top with very little prep.

JimYo 02-21-2010 02:36 PM

1 Attachment(s)
I use a wire buffing wheel to get off the scale ... it shines it at the same time. I think I would paint it with flat black after a primer, but I am in Columbia and you are in Charleston, so if he wants the shinney look, go for a automotive clear coat. If you take it to a automotive shop , cleaned and ready you can probably get a good deal from the shop just to spray it.


OleDog 02-21-2010 03:31 PM

This is a good metal finish for inside metal items from

I mixed up a batch several years ago and keep it stored in a rubbermaid container on the shelf.

I'll heat up the metal with a torch and take a block of it and rub it over the metal. a quick swipe with a buffing rag after it cools smooths out the drips and brings a nice sheen up.


Hobweld 02-22-2010 12:08 PM

Depending on size they make a great clear powder coating that holds up outdoors.


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