Effect of weather on 304 S/S 1

[dalegoldston]

How long will 304 S/S last in an outdoors environment? Where could I find info on this? Would a mil-spec define information like this?

Thanks
Dale

 

[unclesyd]

Come back with a little more information as to the enviroment and what type finish you are exposing. There are things you can do to help it last.

304 SS will tarnish and stain in many enviroments especially if near the coast or a heavy industrial area. Chlorides are its worst enemy and can damage highly strained parts.

304 SS will last forever if you are say 20 miles from the sea shore but will require a little care to maintain a good polished finish.

I personally don't know of a mil spec that covers this. There are specifications on treatments for SS to prevent corrosion which inturn will help prevent tarnishing or staining. Don't take this as the last word.

 

[metengr]

If you need some background information on corrosion of austenitic stainless steels due to atmospheric contaminants, the ASM Metals Handbook, Desk Edition (se page 383) is a good source.

 

[israelkk]

unclesyd

Mil (federal) spec for stainless steels passivation is QQ-P-35

 

[dalegoldston]

Its a 304 S/S no coating that I know of, I believe its a 14 gage thickness with a brushed finish. These are signs used in subways and on streets in locations around New York. This is a question for a friend. He manufactured these with this material and is now being told by the customer that they are rusting,Its probably more of a tarnish. Just looking for information on this and came across this site and looked like a good place. Thanks for the info.

Thanks
Dale

 

[TVP]

MIL-HDBK-729 has some information on this subject:

http://assist.daps.dla.mil/quicksearch/quicksearch_query.cfm

 

[stanweld]

I believe that the first architectural use of 304 type stainless steel was in the Chrysler Building in N.Y. built in the late 1920's. That same s.s. material, somewhat recently cleaned, was essentially uncorroded. It looks fantastic by the way. All that may be required to refurbish the signs is proper cleaning. Iron contamination on the s.s. surface often leads to the "rusting" observed.

 

[mcguire]

The key to making 304 last in a coastal environment ( where 316 is preferred) is to take extra good care of the surface preparation. The absolute worst and most common surface treatment is abrasive polishing. It exposes inclusions and has lots of residual stress; both are bad.
Use 2B, bright annealed, or a rolled-on finish and you will avoid that superficial rust. I solved this problem with rusting gasoline pumps this way and they all use it now.
Go to Allegheny Ludlum and ask for lustrite finish. It looks like brushed but it is put on by steel rolls. Or ask for AK Steel's equivalent. Any service center can obtain it also. All the major appliance and food equipment guys use this finish. It was pioneered by J&L Steel in the early '90s under the tradename Koolline. That company is now being bought by Allegheny.
If you can't switch materials, you can get a little improvement from passivating the surface after polishing.

 

[rollingrock]

If you're building something with many welds you might consider 304L instead of 304 as the 304L has a lower carbon content, thus helping prevent the formation of chromium carbides that can lead to intergranular corrosion
mcguire mentioned Allegheny Ludlum in the previous post. Their data sheet on 304 series stainless steels talks about this. Their home page is

http://www.alleghenyludlum.com/

Good luck,

-MC

 

[IFRs]

Streets and subways pose interesting exposures besides weather - auto and diesel exhaust, acid rain, vandalism, etc.

 

[dalegoldston]

Thanks alot for the Info I will keep this forum bookmarked.

Thanks
Dale

 

[unclesyd]

Here is another very good product for cleaning and polishing SS. I’ve used it with 3M pads and Micro-Cloth with very good results. It is the standard for our laboratory hoods.
Also use it on my boat on all metals.

http://www.sheilashineinc.com/index.htm

On caveat with SS signs or anything portable made from SS is they are prime targets for thieves according to a friend who is in the scrap business.

It pays to bookmark.

 

[davefitz]

Also, one does not need to be near the ocean to have IGSCC issues. Some areas have chlorides in the soil, and wind driven particles or storing the 304H SS on the ground can contaminate a weld and lead to IGSCC .

 

[Salvatio]

If 304ss is to be sensitized, say by heating with a normal torch, as if it is to be welded, and allowed to be cooled under normal environment, say in a workshop (non-corrosive environment), will intergranular corrosion occur to this 304ss?
If I wish to make this 304ss to intergranular corrode under this "normal" condition, what is the least thing that I need to do.

 

[Metalguy]

"These are signs used in subways and on streets in locations around New York."

Hmm, Streets/New York"--I'm thinkin' pizza!

Salvatio,

As stated in the post by Davefitz, it's Cl, Cl and Cl, at least at "room temp".