What grade stainless steel works best in a swimming pool

[pacman454]

Hi! I am designing a surge tank for a local swimming pool and am looking for the best resistants against rust. This will be an enclosed tank. I have seen 304l and 316l rust in these situations. The calcium hyperchlorite level should never reach above 3 ppm. I was thinking 317l would be about the best bet. Any help would be greatly appreciated. Thank you.

 

[gdodd]

Try this Australian web site

http://www.assda.asn.au

 

If you are getting corrosion with a 316 and 304 you will probably get it with 317 also. A 329 might have high enough Cr levels to staveoff corrosion otherwise a duplex stainless or nickel based alloy may be the way to go. You should understand why the 316 material failed before throwing it out as a choice. It may have been improperly handeled or not passivated after installation (but prior to service), or the service condtions may have not been undercontrol. Since duplexes and nickel based alloys are not known to be used in pool construction I doubt you should have to use one.

The key to corrosion control in this situation is properly defining the pH and chloride ion concentration ranges. If the liquid is well mixed preventing cloride concentration in dead spots, stays below 5 ppm and does not get heated above 60°C, 316 should not rust or pit. However if there are excursions outside of these ranges you can get corrosion quickly. Weekly super chloriniation or occassional shut down of flow/pumps, not following the chemical regiment correctly are all possibilities that could lead to adverse conditions. Basically the chloride ions destroy the passive layer of a stainless allowing corrosion to proceed as it would with an alloy or carbon steel.

Also if you have any pipes or tubes welded to this tank the weight of these items may induce stress corrosion cracking in the stainless (even with no apparent signs of corrosion elsewhere) if they are putting a load on the tank. Also poor welding can sensitize the metal to corrosion by depleting the chromium in the weld region. A master welder with experience with stainless or nickel based alloys is highly recommended.

also try asking your question here:

http://licensed-electrician.com:8080/~2

there are pool industry professionals at that board that may be helpful.

good luck

 

[ED1469]

YOU MAY WANT TO GO WITH A182F51 OR A56417-4PH MATERIAL THESE STEELS MAY BE POSSIBILITIES FOR YOU ASTM 1.01 A182 & 564

 

[dwfry]

A stainless tank may not be the answer. Perhaps a lined steel tank, or a non metallic tank would be more suitable?