Thanks for the speedy response, Rich, although it was the response I was afraid to get.

What about some other techniques to give it a polished finish? I was thinking about sandblasting and trying a clear powdercoat but with what you say, how does one avoid the same pitfalls I'm experiencing currently?

I've been thinking about using aluminum for a bright, attractive finish on unpainted items if the steel won't work. I know one needs to be careful to avoid electrolysis but are there any other drawbacks to using aluminum rather than more costly stainless steel?

There is NO finish for steel that will not rust when exposed to water vapor. Any surface treatment that increases the surface area of he sheet, such as sanding, sandblasting or peening, is just exacerbating the problem. More surface area = more room for oxygen to bond with iron and make rust.

There is NO surface coating that will absolutely, totally, 100% exclude air and/or water vapor. And in fact, the tougher the surface you apply (say, powdercoating) the greater the odds that you will get rust beneath it. It only takes one holiday that size of a water molecule to allow the rust to begin. It's all downhill from there, with he powdercoating retaining the moisture beneath itself and further promoting rust.

I'd use stainless steel. If that is not an option then I'd probably try aluminum and have it clear anodized as Daedalus recommends. The aluminum oxide surface created by the process of anodizing is extremely durable and far more resistant to scratching than any paint or powdercoat. Electrolysis is not much of an issue as long as you have no other metals in contact with the aluminum. Look at ow nicely old aluminum cookware holds up over the years. Salt air, of course, will raise hell with it, but you could delay that a long time with a good quality clear coat over the freshly anodized aluminum.

Sorry I can't offer a magic solution to your dilemma. The only "silver bullet" I know of would be fine silver and that's a mite pricey these days. :-)

Rich

Al-u-minium!
Make it,flap wheel it,clear anodize it.
You could also use whatever the motorcycle companies are presently using on their aluminum side covers.I think it`s just clear powdercoating that Harley Davidson uses.

Carbon steel is NOT the way to go here.Many have tried and all have failed.Some just fail quicker than others.

In theory there is no difference between theory and practice.
In practice there is.

Do you have any experience in maintaining a flawlessly polished finish on mild steel? It doesn't necessarily need to be flap-wheeled although I find it to be quite attractive.

What surface prep process do you recommend?

I do maintain a near-flawless polished surface on my metalsmithing hammers and stakes. I do that by polishing them to as near a mirror finish as possible and then waxing them with Renaissance Wax. The Ren wax is much more costly than clear coat ($25 per 1/4 pt), but better for the purpose. What really keeps them shiny though, is that they are stored in wooden drawers with a bit of camphor and they get used regularly, being buffed a bit and re-waxed after pretty much every use. Not something that you're likely to do with a metal sign.

When I was in the sign business I made a large number of signs from metal and tried every clear coat available, so I'm speaking from experience when I recommend stainless. Your time is far more valuable than the cost of the sheet stock, after all, and the time you save by not having to do a surface finish is very significant. Something to think about.

Rich

You can get stainless to rust fairly easily too,all you have to do is use a wire wheel made of HCS instead of stainless or a buff that was used for carbon steel on it.Welding or forging and not passivating or grinding the heated surfaces back will get you rust too.
When I was making deck hardware and fittings for yachts we finished the stainless with wheels that we had clearly printed with "stainless only".If you used it(even once) on steel you didn`t use it on the stainless.
Not all stainless is created equal either.We used 316 for fittings exposed to salt air.Some of the other grades will discolor or rust under continued exposure to heavy humidity.

In theory there is no difference between theory and practice.
In practice there is.

You're right, the cost of stainless really isn't so bad when one considers all the upsides. I really think I'm going to begin with aluminum though to keep my costs down, I'm unemployed and this is the only thing I have to raise any sort of income with the job situation the way it is. I'm working with very limited funds.

Thanks for sharing your knowledge, much appreciated.

The Permalac web site

http://www.permalac.com/technicalfacts.asp

has a pretty comprehensive advice on procedure for preparation of different types of surfaces. I am not sure what their "No. 69" and "No. 500" thinners are, 69 sounds suspiciously like acetone and it behaves like it. Like acetone it can leave behind oily streaks.

Getting all the residual water off the surface is important.

FWIW, here is my trial of rust preventing chemicals. PM me for the whole protocol if you are interested:

http://www.flickr.com/photos/27683124@N07/sets/72157623384305382/

crquack

Thanks Jake.

That particular sign will be going to horse shows as a stall display so while it will be mostly indoors there is still going to be a lot of exposure to the elements with being lugged around, plus sawdust tends to hold a lot of moisture, etc.

I really like the permalac from what i've seen, I was just looking into it yesterday and was impressed by how durable it is, plus it would be excellent for something like that sign because it is pretty abrasive resistant. I think that at the very least I will be using permalac to seal the primed/painted signs to keep the weather out.

Re: drying with towels. Is there a certain material besides cotton which won't tend to pull off and leave fibers all over the work piece as i wipe it down?

I prefer a real chamois over anything else.

The locations that the sign will be used should be treated as out doors in this instance. By inside I meant somewhere with AC/Heat that keeps the place within a window of temp and humidity. For these location and the fact that it will be moved often, one nick through the clear coat and all bets are off, I say stainless is the way to go.

Jake

Jake Balcom
Mettle Design
Lincoln, NE

Thank you Reis.

I've been looking into anodizing aluminum and it's just going to be another costly step with time being the biggest constraint, just going to have to offer stainless as an optional finish at a higher cost.

I'm operating with a very small 110 miller plasma and a 110 lincoln 140t out of my inlaws garage currently. Cost is the number one factor in my operation at this point. Been lurking on this site for many months but couldn't afford to anymore with the knowledge here, looking forward to- and appreciative of everyone's help. Thanks again.

that's beautiful, thanks for the tips. What was your cost for the powdercoat?

The Aussie is about .90 on the USD so roughly par.

the clear powder coat was $59A or $45US and considering that this was 800mm in diameter and about 250mm deep.
FYI the face was made of 3mm punchouts used like a metal mosaic and the suround is plasma cut out of a donut shaped auto LPG tank.
Regards TC

Cool. That's a pretty decent price, lower than I would expect.

Thanks for the input everyone. Have a guy from our church who today decided he would like a sign for inside his cabin retreat, he wants it polished.

So I'm going to look at some SS tables for sale tomorrow I came across on Craigslist. Should be about the most effective way to play this dilemma.