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Re: 304 Stainless signs.....rusting!

I know Jim got his answer but for what its worth; I've seen vinyl siding, concrete and an aluminum sign "rusting", it was the high content in the water common in NH sprayed from irrigation sprinklers .

Re: 304 Stainless signs.....rusting!

Thanks Jim, It was just a shot to see if you recalled.

Manokai, I am fully aware of the issues with free iron on SS, the interaction of that with welding, and the need to isolate tools and equipment from plain steel work to avoid contamination of SS. My intention is to pickle all HAZ areas first, but then I need to do something to get a uniform finish as most components will be mill finish. I am going to make something very much like the "crap" that Barn118 did for fence panels in this thread: http://weldingweb.com/vbb/showthread.php...+i+like+making

(Yes, I fully understand railing codes also.) Now looking at this, I see no possible way of polishing that all up. Plus i really don't want a bright shiny finish. There are just too many individual thin components to be able to polish all that. I suppose the "grass" could be pre-polished by making some sort of a multiple-buffing wheel setup that you could pull a rod through prior to welding, and then you just have to hit the HAZ and other affected areas after it is welded up, but my experience in finishing is to do it all at once, or it will not look uniform. So my intention was to pickle the welded areas to get them back up to full SS level protection, and then to blast the entire assembly to get a uniform, light matte finish. I would probably also pickle any other areas that seemed to be showing or indicating rust, prior to any blasting. Probably with Citristrip products to make the hazards of pickling reasonable.

Blasting will need to be from a clean system that never touched plain steel. Right now I am thinking of using 60-120 grit glass beads based on a thread I saw on Practical Machinist on this topic. I have also considered electropolishing, but that is not easy to come by for very large parts like 3.5'x8'+ railing sections, and those sort of places only want to deal B to B, not with dorks like me.

These are residential porch/deck railings and not in a coastal area, so salt exposure is nil. Based on the fact that Jim is saying the signs look great 2-3+ yrs later after a proper blasting with clean SS-only equipment, I am confident that that level of finish will not be a major headache in this application.

With that said, i am still open to and exploring options. You build railing panels from many rod pieces like in the linked thread, and how would you recommend/handle a finish?

Thanks,
Dave

Edit: I reviewed the link you posted, and was familiar with everything in there with the exception of the methods of testing for free iron, so thank you for that.

Re: 304 Stainless signs.....rusting!

It has been a few years since this was posted....I do not know what the stainless signs were blasted with. Jim Colt

Originally Posted by davec

Jim, any idea what media they used to blast this? I'm looking for finish ideas for some outdoor SS railings I will be doing on my house next summer. Right now I'm thinking glass beads, 60-120 grit to get a nice uniform light matte finish.

Thanks,
Dave

Re: 304 Stainless signs.....rusting!

@ davec - recommend you explore the "why?" of 'free iron' associated with stainless steel by reading post #66 in the metallurgy thread.

SS is typically cleaned with Nitric and HF acids to remove 'free iron', and then neutralized with baking soda {critical}. The preferred mechanical removal technique incolves are flapper and unitized wheels, with unitized being optimal.

Glass beading SS, nor using wire brushes, is not/not recommended as the approach will induce micro pits into the SS and further promote corrosion.

Re: 304 Stainless signs.....rusting!

Jim, any idea what media they used to blast this? I'm looking for finish ideas for some outdoor SS railings I will be doing on my house next summer. Right now I'm thinking glass beads, 60-120 grit to get a nice uniform light matte finish.

Thanks,
Dave

Re: 304 Stainless signs.....rusting!

The media blasting leaves a rough surface that is not ideal for stainless steel especially if you are leaving it outside. The rough surface allows contaminates that are naturally blowing around to rest on your sign and rust. If you want the look of the media blasting you will have to clean it often. To make it more ideal it would be better to go with a 400 grit finish or greater smother is always better. You should still clean it and apply a product like Sheila Shine.

Re: 304 Stainless signs.....rusting!

If the signs get a little grody again, clean them off with Barkeepers Friend cleanser.

Re: 304 Stainless signs.....rusting!

I work in food process sanitary stuff ..308..316..it rusts..most of it is also magnetic

Re: 304 Stainless signs.....rusting!

Originally Posted by sjames

im no expert on the process, but it involves a heated bath in a nitric acid solution.

one source lists 20% nitric acid at 140F for 30 minutes.

Also not an expert but the aerospace company that I used to worked for called for it on EVERYTHING that they made from SS. My understanding is that by briefly soaking in strong acid, the SS forms an oxide layer that will protect it from further oxidation by weak acids, weather, etc. However they did it, the process worked WELL. I seem to recall that they used Potassium Dichromate in addition to Nitric Acid.

Re: 304 Stainless signs.....rusting!

Originally Posted by jimcolt

I don't think so....I am the original poster on this thread. Was looking for advice....which I got a couple years ago when it was first posted! Not sure where you see a product being promoted?

Jim Colt

They were referring to a spam post where a guy was trying to push electropolishing equipment, which was removed by the moderators. I can see where the misunderstanding came from.

Re: 304 Stainless signs.....rusting!

i am guessing you cut those on the same plasma table you cut steel (maybe water table after cutting steel), or on a steel stand off and now you are contaminated. stainless only need mixed with stainless. We pressure test items, and if we pressure test steel in our tank it contaminates the water and we see similar issues with our stainless products. gotta segregate.

Re: 304 Stainless signs.....rusting!

Originally Posted by jimcolt

If that was the case only the plasma cut edges would have rusted. The signs were reblasted in a shop that only handles stainless. It has been a couple years and they all still look great. No clearcoat.

Cutting with an abrasive waterjet would have made signs with a tighter tolerance, not at all necessary. They still would have needed shot blasting for the desired finish.

Jim Colt Hypertherm

The rest of the rust could just be transfered from where it originated from. Water will move rust staining around. These ARE outside. It's pretty obvious the worst spots are in the HEZ.

Re: 304 Stainless signs.....rusting!

From what I've heard that sounds legit based on my experiences, getting stainless really hot will burn off some of the chromium content. If you notice, the problem areas are in the heat affected zones where it was cut.

I don't recall all the properties of the different grades of stainless, but in my experience, 304 isn't meant to stay rust free. Its used a lot in exhausts where looks don't really matter. 316 tends to be the most common for cosmetic fixtures.

Re: 304 Stainless signs.....rusting!

And?...

Re: 304 Stainless signs.....rusting!

What is Stainless Steel in few words. (rust problems)

Stainless steel is an alloy of iron which contains at least 10% chromium (Cr).
This addition of chromium defines the unique properties [stainless, corrosion and heat resisting].
The chromium content of the steel allows the formation of an invisible, corrosion-resisting chromium oxide film on the steel surface.
If damaged mechanically or chemically, this film is self-healing, providing that oxygen, even in very small amounts, is present.
A common form of rusting stainless steel is after the stainless steel has been exposed to very high temperatures (400-850°C) or (750-1550°F).
If this happens, sensitization can occur which is where the carbon and the chromium bond together in the stainless steel and form carbides.
These carbides situate themselves at the stainless steel grain boundaries, and the grain boundaries become deficient of chromium.
With lower chromium concentrations at the grain boundaries, the chromium oxide protective film can become discontinuous and start rusting.
The best solution is to polishing the overheated and the nearby areas using suitable abrasive brushes and polishing pastes.
This process is able heal the points of chromium oxide film that they has damaged.
At reality we do a very thin and smooth grinding/cleaning of the carbon carbides (that has come out at the surface from overheating).
So, removing the tiny steel particles we help the chromium oxide film to be able again, to self-healing the stainless steel.

Chemical Composition
Stainless Steel AISI 304

Carbon 0.08% max.
Manganese 2.00% max.
Phosphorus 0.045% max.
Sulfur 0.030% max.
Silicon 1.00% max.
Chromium 18.00-20.00%
Nickel 8.00-10.50%

Chemical Composition
Stainless Steel AISI 316

Carbon 0.08% max.
Manganese 2.00% max.
Phosphorus 0.045% max.
Sulfur 0.030% max.
Silicon 1.00% max.
Chromium 16.00-18.00%
Nickel 10.00-14.00%
Molybdenum 2.00-3.00%

Happy New Year
Bill

Re: 304 Stainless signs.....rusting!

That guy push his luck too far. Must be a rookie

Re: 304 Stainless signs.....rusting!

Originally Posted by Pipeliner

Well thank you Teggy1 for beating me to the punch by 9 minutes and ruining everything I thought so hard on to try to put into words!!!!!!!!!!!!

2017 is just not going to be my year from the looks of it. First the scammer guy confusing every body. And now Teggy1 ruining my post by posting the exact same thing I was going to say!!!!

[edit: I'm really not mad at Teggy1. This whole post was in jest. No one take anything seriously. No hard feelings. Except for the scammer guy. And rust.]

No worries man!

I'll try not to do it again.

Re: 304 Stainless signs.....rusting!

Originally Posted by Teggy1

There was a poster posting the same stainless finishing equipment in all kinds of threads. They posted here as well, thus the old thread revival. It appears the administrators removed him and his posts, leaving voids in the conversation.

Well thank you Teggy1 for beating me to the punch by 9 minutes and ruining everything I thought so hard on to try to put into words!!!!!!!!!!!!

2017 is just not going to be my year from the looks of it. First the scammer guy confusing every body. And now Teggy1 ruining my post by posting the exact same thing I was going to say!!!!

[edit: I'm really not mad at Teggy1. This whole post was in jest. No one take anything seriously. No hard feelings. Except for the scammer guy. And rust.]

Re: 304 Stainless signs.....rusting!

Originally Posted by Showdog75

I think the said poster got the boot for trying to push his product.

Originally Posted by jimcolt

Not sure where you see a product being promoted?

Jim, Showdog was referring to "the said poster" that VW was referring to.

Some d-bag scammer posted the same thing on several old threads. The mods removed him and deleted his posts. And now here we are stirring up 3 year old stainless steel dust! And the damn sign will probably start rusting again!! Thanks a lot you scammer guy who got deleted and left us with this to deal with to start off 2017!!!!!!!

We all know you're legit Jim Colt.

Re: 304 Stainless signs.....rusting!

Originally Posted by jimcolt

I don't think so....I am the original poster on this thread. Was looking for advice....which I got a couple years ago when it was first posted! Not sure where you see a product being promoted?

Jim Colt

There was a poster posting the same stainless finishing equipment in all kinds of threads. They posted here as well, thus the old thread revival. It appears the administrators removed him and his posts, leaving voids in the conversation.

Re: 304 Stainless signs.....rusting!

A rough surface will hold debris. If the signs are outside it is possible that it collected enough junk from rain to rust. With pretty much any metal the smoother the surface the more resistant to "stuff" it is. This is especially true with stainless, if the sign was polished it would resist rust much better.

Re: 304 Stainless signs.....rusting!

I don't think so....I am the original poster on this thread. Was looking for advice....which I got a couple years ago when it was first posted! Not sure where you see a product being promoted?

Jim Colt

Originally Posted by Showdog75

I think the said poster got the boot for trying to push his product.

Re: 304 Stainless signs.....rusting!

Originally Posted by Showdog75

I think the said poster got the boot for trying to push his product.

Well that makes sense.

Re: 304 Stainless signs.....rusting!

Originally Posted by jimcolt

If that was the case only the plasma cut edges would have rusted. The signs were reblasted in a shop that only handles stainless. It has been a couple years and they all still look great. No clearcoat.

Cutting with an abrasive waterjet would have made signs with a tighter tolerance, not at all necessary. They still would have needed shot blasting for the desired finish.

Jim Colt Hypertherm

Thanks for the update. I always like learning solutions to problems that have worked for other people.

Re: 304 Stainless signs.....rusting!

Originally Posted by vwguy3

Huh?, the post before yours is from 2013.

I think the said poster got the boot for trying to push his product.