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Electrical equipment enclosures 5

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Herk

Herk

Electrical
May 6, 2003
4
Cut me some slack because I'm an EE, but in Hawaii, when specifying outdoor equipment enclosures for DoD land-based projects, we call for 304L or, preferably, 316 stainless steel. High humidity and chlorides quickly corrode other steels, supposedly 304 stainless too.

Three issues:
[1] Equipment manufacturers are generally reluctant to provide the preferred 316 stainless enclosures because the material is brittle and hard to work. Is this a valid excuse?
[2] Is 316 stainless suitable for hardware (bolts, nuts, etc) due to its brittle nature e.g., if subjected to vibration?
[3] Is 304L more impervious to chloride corrosion than 304?

Due to one or more of these concerns our clients end up with 304L stainless enclosures and hardware, which, according to my reading, is more vulnerable to corrosion from chlorides than 316 .
An equipment manufacturer I recently consulted said his company will only provide 305 stainless steel for use in Hawaii. Would this be a better option?
Would appreciate any advice you can offer.
 
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[1] No, this is not a valid excuse. 316 is not brittle, and will perform quite similarly to 304.

[2] Type 316 is a very common grade for stainless steel fasteners. It can be cold worked (forged) or machined.

[3] 304L has essentially the same corrosion resistance in chlorides as 304. The others can provide more specific info.

Regarding 305, this is typically used in bar or wire applications, since the increased Ni content vs. 304 (10-13 vs. 8-10 reduces the amount of work hardening during forming/forging. The Ni content does not confer much improvement in chloride resistance. Mo is the key here, and 316 with ~ 2% Mo is the minimum you should be using in outdoor environments. A duplex alloy like 2205 may also be an option. Others will be along shortly with more advice...
 
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Herk

Have a look at the Nickel Institute Development web site they have some information on this. Or the Australian Stainless Steel Development have performed some very good work on use of stainless steels in costal environments. Particularly in relatin to tea staining.

Regards
Mark Hutton
hutton4eng@picknowl.com.au
 
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I have worked with a lot of companies on making exterior stainless enclosures. One group that took the challenge seriously was the gasloine pump manufacturers, whose product is not only exposed to warm coastal environments, but it is also under cover, and so unwashed by rain which would be quite beneficial.
Their old standard, #4 polished 304, began showing slight corrosion in coastal installations as service stations went to covered pumping areas, which was unacceptable. They tried polished 316 unsuccessfully and had even tried to get 317, when we suggested they try a bright annealed 304 which had a imprinted finish to resemble #4 polish. All corrosion problems were eliminated. We had had equal success with commercial kitchen equipment in such environmeents previously.
The key was the surface finish rather than the grade per se. When we talked to the outdoor electrical enclosure people, we had no luck gettin them to budge from their #4 polish which suited their shop practices of grinding welds.
It sounds like they still haven't figured it out. If they won't listen to their customers or their suppliers, I don't know how to get through to them.
 
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mcguire,

According to the ASSDA research surface finish is certainlly the key to surface corrosion.
Mark Hutton
hutton4eng@picknowl.com.au
 
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I normally do not require any particular finish for my industrial applications. However, type 316 stainless steel enclosures are readily available. We may use a panel shop if a standard enclosure does not fit our applications. You may need a rating of NEMA 4X; IP 65 or 66.

Check these links:



John
 
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We have actually done some toll pickling for an enclosure user. He knew that the finish was causing problems, even on 316. We pickled the boxes for him and greatly improved the corrosion resistance.
They aren't as pretty, but work much better.
The smeared metal from the polish form crevices that trap impurities and are locations for easy initiation of corrosion.

When it comes to resisting chloride pitting you need to look at the Cr and Mo content of the alloy. And to be honest, the Nitrogen also. For austenitic stainless grades the formula that correlates with crevice corrosion resistance is roughly Cr + 3.3xMo + 16xN.
At todays prices a lean duplex grade like 2003 or 2101 would give as much corrosion resistance as 316, higher strength and lower cost.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
 
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EdStainless
Is there a data sheet on 2101 on the web? I know Allegheny publishes a blue sheet on 2003.
 
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LDX2101 is the Outokumpu alloy. Their web site is a bitch.
Try this, I have asked for some additional tech data and it has been very slow in coming.

There is also the older 2304. Very good for caustic service, but not of any great general interest.
AK makes 19D. I don't care for it.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
 
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As the leader of this forum I believe the response from Rolledalloy is appropriately technical and non-commercial.
Everyone is selling something and we need people with knowledge to share. Thanks for the input.
Mike McGuire

Michael McGuire
 
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