Chloride limits for stainless steels
Chloride limits for stainless steels
(OP)
We are chosing materials for a multistage sump pump for the retention pond for the hot lime softener blowdown. The normal operating temperature is 5C with upsets to 98C (cannot quantify how often there will be upsets). Chlorides are 4800-22000ppm and there is 5% lime sludge (i.e. erosion from magox crystals). pH is 9.5 and the water is oxygenated.
1) 12Cr is an option, although I do not know how 12Cr reacts to 22000ppm Cl-. We also do not know how severe the pitting will be.
2) Hard chrome plating could be used, but again I do not know how severe the Cl- pitting would be.
3) Would super duplex (e.g. 2507) stand up to this environment assuming the worst case of 98C and 22000ppm Cl-?
4) Any other options for materials (other than Hastelloy/Inconel)?
Thank you very much for any help you can provide!
1) 12Cr is an option, although I do not know how 12Cr reacts to 22000ppm Cl-. We also do not know how severe the pitting will be.
2) Hard chrome plating could be used, but again I do not know how severe the Cl- pitting would be.
3) Would super duplex (e.g. 2507) stand up to this environment assuming the worst case of 98C and 22000ppm Cl-?
4) Any other options for materials (other than Hastelloy/Inconel)?
Thank you very much for any help you can provide!





RE: Chloride limits for stainless steels
Low temp helps, higher hurts.
Higher ph helps.
Abrasion hurts.
In pumps I like to think of the parts in an order of how critical thy are. First is the shaft, it must survive. A cold worked "C" alloy (C276, C22, 59 or 686) would be a good place to start. Then the impellers, a super duplex will offer good pitting resistance and the high strength will offer at least some abrasion resistance.
The bowls are the least critical parts. If anything goes wrong you want them to corrode first and provide galvanic protection to the other parts. You might look at a 6% Mo superaustenitic grade.
You can't make all of the parts last forever, but you can control how it fails.
= = = = = = = = = = = = = = = = = = = =
Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net
RE: Chloride limits for stainless steels
S.
http://www.corrosionist.com
RE: Chloride limits for stainless steels
RE: Chloride limits for stainless steels
RE: Chloride limits for stainless steels
I would look into CK3MCuN (6Mo), CN3MN (6Mo), or a patented alloy Alloy 31 (7Mo). Of all of the alloys, the Alloy 31 has the highest numbers for PRE and CCT, without getting to the Hastelloy / Inconel range.
The patent holder is MetalTek International in Wisconsin, if you have trouble finding them.
RE: Chloride limits for stainless steels
In complement to others suggestions I would add SEA-CURE S44660 and also AL-6XN
For more information about this subject go to:
http://www
luismarques
RE: Chloride limits for stainless steels
I would have a troll through the hits in the following:
http
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: Chloride limits for stainless steels
Thank you very much to SJones for the Google hits. I read through the desalination papers/info and it looks like 254SMo and superduplex are frequently used. I could not find process information regarding what temperatures and chloride concentrations are typical in desalination plants. I do not have experience specifying superduplex for 22000ppm and 98C...I guess I don't have that "warm fuzzy feeling" due to my lack of experience.
Can superduplex (such as 2507) be used successfully as a pump impeller at 98C and 22000ppm chlorides? I looked in MTI 27 and MTI 15, but only 2205 is on the graphs (although I wouldn't use 2205 in this case).
RE: Chloride limits for stainless steels
http:/
you see that the limit is approx 90°C.
In terms of Stress Corrosion the limit is well above and it's not a concern.
the problem at this point is not only the impeller, which materials will you select for the rest of the plant to work at 98°C with something very close to seawater? you should go to a nickel alloy to withstand such a conditions in my opinion.
regards
S.
http://www.corrosionist.com
RE: Chloride limits for stainless steels
I have a suggestion regarding corrosion information for stainless steels and duplex steels. Go to the web site below and request the Corrosion Handbook by contacting Outokumpu directly. They have an on-line version, however the hard copy is what you need because it contains more comprehensive information. I had received it in the mail some time ago.
http://
RE: Chloride limits for stainless steels
Go for 25Cr super duplex with a minimum PREN of 40 - peanuts difference in price.
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: Chloride limits for stainless steels
The impellers must be tough, a superduplex or superaustenitic would work.
You do not want to use the same material for all parts of the pump. The service is enough different that you would suffer early failure of impellers if all parts were the same.
The bowls could be a lesser material, maybe even a type 2 NiResist would work.
Don't use a 12%Cr for any parts and don't rely on plating.
= = = = = = = = = = = = = = = = = = = =
Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net
RE: Chloride limits for stainless steels