duplex 2205- max chloride level = ?
duplex 2205- max chloride level = ?
(OP)
WE have built a series of FGD scrubbers for our coal fired power plants. The scrubber mfr claims the 2205 components are suitable for slurry chloride content as high as 30,000 ppm. The blowdown system and wastewater bioreactor was then sized for a systegm chloride content of 20,000 ppm chlorides.
After 1 yr of operation, severe crevice corrosion at flanges and access hatches was evident; annual average Cl content was 16,000 ppm Chlorides with 5.5<pH<6.5 , SO2 and O2 bubbling thru the slurry.
Can anyone advise published corrosion curves for 2205 in a process solution similar to the above described process? As per the Corrosion Handbook ( Outo Kumpu 9th ed pI:88 fig 1) 2205 is only suitable to 2000 ppm chlorides. Other utilities typically run to not greater than 8000 ppm chlorides.
It looks like our goose is well cooked.
After 1 yr of operation, severe crevice corrosion at flanges and access hatches was evident; annual average Cl content was 16,000 ppm Chlorides with 5.5<pH<6.5 , SO2 and O2 bubbling thru the slurry.
Can anyone advise published corrosion curves for 2205 in a process solution similar to the above described process? As per the Corrosion Handbook ( Outo Kumpu 9th ed pI:88 fig 1) 2205 is only suitable to 2000 ppm chlorides. Other utilities typically run to not greater than 8000 ppm chlorides.
It looks like our goose is well cooked.





RE: duplex 2205- max chloride level = ?
What is your temp?
At your pH I would stick to 2500-3000 as an upper end for crevice corrosion. For parts that only see bold face exposure (pitting and not crevice) then 5,000 should work.
I can't see using 2205 at 16,000 under any situation.
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Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net
RE: duplex 2205- max chloride level = ?
Yes, it sounds like your FGD goose is cooked. We had contemplated a wet FGD for our two units and 2205 was proposed. Similar conditions to yours more or less, and I told the manufacturer no way. You need either a 6Mo or better material. Basis for the decision was as follows;
Special Metals, "Experience in Effective Application of Metallic Materials for Construction of FGD Systems", Shoemaker and Crum
"Corrosion Performance and Field Experience with Superduplex and Super Austenitic Stainless Steels in FGD Systems", Audouard, Verneau and Grocki
RE: duplex 2205- max chloride level = ?
Ok, another star then.
I found the shoemaker paper right after I posted; it is an ecxellent paper. Other papers by Shoemaker, Crum, specialty metals, etc highlight the importance to "overmatch" or "overalloy" the first pass weld consumable when plating CS or wall-papering a component with 2205 or hastelloy- that is the general solution we are using to address these local crevice corrosion issues. Also resorting to rubber liners and flake glass. Job security for maintenance welders.
another concern with these concrete absorber vessels is potential to corrode the CS rebar in the concrete. Initial concern is at access hatch frames, but general rebar corrosion may be a concern if chlorides can migrate by osmotic pressure thru concrete.
RE: duplex 2205- max chloride level = ?
In any system the risk of permiation and weak joints needs to be carefully considered.
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Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net
RE: duplex 2205- max chloride level = ?
a) welds must be over matched- we have had problems with welds which were not over matched
b)crevice corrosion locations require add'l protection-flanges, hatches, dead zones
c)any zone with potential for condensation of H2SO2/H2SO4 require the 6 Mo alloys.
RE: duplex 2205- max chloride level = ?
ht
Here are other publications that can be of interest:
Special Alloys and Overmatching Welding Products Solve FGD ...
http://
WELDING AND FABRICATION IN NICKEL ALLOYS IN FGD SYSTEMS
http://
FLUE GAS DESULPHURIZATION; THE EUROPEAN SCENE
http://
THE USE OF NICKEL STAINLESS STEELS AND NICKEL ALLOYS IN FLUE GAS DESULPHURIZATION SYSTEMS IN THE UNITED STATES
http://
LIFE-CYCLE COST COMPARISON OF ALTERNATIVE ALLOYS FOR FGD COMPONENTS
http://
Hope this help you
S.
http://www.corrosionist.com
RE: duplex 2205- max chloride level = ?
2205 has been well tested in seawater and is resistant at ambient if no crevices are present. Your prolem seems pH and temperature aggravated.
Michael McGuire
http://stainlesssteelforengineers.blogspot.com/
RE: duplex 2205- max chloride level = ?
Below is a reference to a paper presented at AirPol 2004 by Sargent & Lundy. They set 12,000 ppm Cl as a design limit for 2205, with an excursion max of 20,000 ppm Cl. Here, “excursion chlorides” are defined as the maximum chloride concentration at which the tower could operate for several months without material degradation. The safe level of operation is not at the maximum chloride concentration, but at the level of “design chlorides.”
AIRPOL 2004 (Available from NACE. www.nace.org)
FGD MATERIALS OF CONSTRUCTION SELECTION AND OPTIMIZATION OF FGD AND WASTEWATER TREATMENT SYSTEM DESIGN
Steve Katzberger Sargent & Lundy
steve.m.katzberger@sargentlundy.com
RE: duplex 2205- max chloride level = ?
as per cooling tower mfrs' and slat water road bridge specs, the concrete vessles in FGD service should use low permiability specs , usually requiring use of micro silicas or silica fume or flyash replacement, superplasticizers, tested to less than 1000 coulombs permiability at 28 days. If sulphates above 1000 ppm or langelier index is not positve, then a lining may be required. Florida DOT tests indicate epoxy coated rebar ECR has no corrosion advantages after a few years service.
RE: duplex 2205- max chloride level = ?
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Plymouth Tube
RE: duplex 2205- max chloride level = ?
And following on from that, does Cl- resistance of series 300 stainless steel improve with increasing pH?
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