Metal and chemicals

[davidwrogers]

316 Stainless is the appropriate metal for making trays out of? Look for resistance to chemicals and no inadvertent reactions. I'm no chemist but I want to do this right.

[Pawlowski6132]

I don't know.

[vinny]

yeah, stainless is a great material. I could use a couple 30x40's while you're at it.

[Greg Blank]

316L from a cost factor is probably the best coupled with corrioson resistance. 321 could be better corriosn wise but its a lot more expensive. Are you making the trays yourself? I have a set of three 20x24 stainless trays that were made custom for me- most likely 316L. If I had had to have paid for them to be made best guess would about $300 each minimum -over ten years ago. If this a sporiac use I would consider plastic, or maybe a dyi fiberglass single tray.

[Leigh]

Assuming you plan to weld the seams, alloy 321 would be preferable.
It's a corrosion-resistant alloy like 316, with added titanium to improve weldability.

It's not terribly expensive. McMaster-Carr has 12"x36"x0.032" sheets for $60.
Finding someone who can work it properly is a different question.

I would shy away from 316L for this application due to the added lead (the L suffix),
which might make it a bit more reactive than regular 316.

- Leigh

[Greg Blank]

You are wrong L does not mean Lead content. http://en.wikipedia.org/wiki/Stainless_steel

The "L" means that the carbon content of the alloy is below 0.03%, which reduces the sensitization effect (precipitation of chromium carbides at grain boundaries) caused by the high temperatures involved in welding.

No lead found here either.
http://www.upmet.com/316-chemical.shtml

316 of any type is about 3x less expensive than 321. Making a large tray, you would be bending the sides upward from the same sheet, you also should not be seaming a tray rather using a single continuos sheet and cutting the tray from a single large sheet (Like a 36x48 or a 36x96 sheet). so that a rough spot does not require grinding. Grinding seams will offer areas that will potentially cause problems, like scratches etc. BTW I actually do weld.

[Nathan Potter]

I think 316 SS is a good bet. I had a couple of smaller trays made some years ago. The sides were bent up from a single sheet as Greg suggests above so only the corners needed welding. The fabricator used heliarc welding and did quite a beautiful job. These are indestructible but do stain with a variety of chemistries. As far as I can tell the stains are a surface oxide that is very thin but sometimes thick enough (maybe 200 to 1000å) to show an interference color. I just use fine scotch brite to occasionally clean off the surface oxide.

Research laboratory people I once worked with used aqua regia (HCL/HNO3) mixture to violently etch clean stainless but that does significant pitting of the alloy as I recall, plus is incredibly noxious. Scotchbrite leaves a nice satin finish with no stink.

Nate Potter, Austin TX.

[Drew Wiley]

316L is generally specified if the corners need to be welded (it's easier to weld). Otherwise, most 300-grade stainless products are suitable. Acrylic plastic is easier to fabricate and more chem resistant. But used trays, stainless or otherwise, are avail used
at fairly low prices, unless you need something odd. Welded trays are often suspect because it hasn't been done right and the weld itself becomes susceptible to corrosion.
Stamped trays are better. I like stainless simply because it responds to temperature much
better in a water jacket than plastic.

[Sevo]

Photo chemistry tends to interact with silver - as such, it is not granted that it is stainless steel safe. However, available pre-mixed photo chemistry, in particular just about anything also sold for large scale processing, has been designed to be stainless steel safe. Specifications often demand 316Ti (in Europe a.k.a. 1.4571 or V4A), but other 316 varieties should be good enough. If you are into alternative processes, you'll have to check by substance - some of the more arcane 19th century processes will cheerfully eat holes into stainless steel and emit poisonous fumes while at it...

[Greg Blank]

Good points, Strong enough acids might emit enough chromium compounds to be considered an issue, when welding stainless hexavalent chromium is considered an occupatienal hazard to be addressed..... http://www.osha.gov/SLTC/hexavalentchromium/index.html

I agree with the stamped tray statement- however TIG welding "Heli arc" should give really nice welds for this sort of stuff- which is why I bought a Lincoln 175 Square wave last year, stamped though, that would be ideal- or one could go to Harbor Frieght and get a plastic welder "Maybe". & I have that set of trays, FWIW they were produced by my friend Jeff who was the Arkay welder w/20 years experience welding when Arkay was part of Omega Arkay. He did the trays and a small 24 x 36" sink for me as compensation because shot his wedding photos (Wanna see? "The trays that is".