duplex 2205- max chloride level = ? 3

[davefitz]

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.

 

[EdStainless]

For heat transfer applications we advise a limit of about 5,000ppm at neutral pH.
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

 

[metengr]

davefitz;
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

 

[davefitz]

Meteng.

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.

 

[EdStainless]

There are some good presentations from Usinore on the different grades of stainless to use in different zones of FGD.
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

 

[davefitz]

The paper by Audouard et al referenced by Meteng confirms the mfr's recommendation: that alloy 2205 can be used to Cl concentrations to 30,000 ppm to a pH as low as 5.5, in some zones of the FGD system ( see their fig 5). One should add some caveats:
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.

 

[strider6]

If you look at this presentation, pag 10, there is a good graph with Chlorides and pH application limit for various materials in FGD.

http://www.imoa.info/FileLib/Applications_Mo_Environmental.pdf

Here are other publications that can be of interest:

Special Alloys and Overmatching Welding Products Solve FGD ...

http://www.specialmetals.com/docume...ing Products Solve FGD Corrosion Problems.pdf

WELDING AND FABRICATION IN NICKEL ALLOYS IN FGD SYSTEMS

http://www.corrosionsource.com/technicallibrary/nidi/literature/pdf/10027.pdf

FLUE GAS DESULPHURIZATION; THE EUROPEAN SCENE

http://www.corrosionsource.com/technicallibrary/nidi/literature/pdf/10025.pdf

THE USE OF NICKEL STAINLESS STEELS AND NICKEL ALLOYS IN FLUE GAS DESULPHURIZATION SYSTEMS IN THE UNITED STATES

http://www.corrosionsource.com/technicallibrary/nidi/literature/pdf/10024.pdf

LIFE-CYCLE COST COMPARISON OF ALTERNATIVE ALLOYS FOR FGD COMPONENTS

http://www.corrosionsource.com/technicallibrary/nidi/literature/pdf/10023.pdf

Hope this help you

S.

http://www.corrosionist.com

 

[mcguire]

Be careful of the nidi material. It gives borderline misinfomation to not make duplex look good.
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/

 

[rolledalloy]

One of the longest running FGD installations of 2205 material was the First Energy Burger Plant in Ohio. 2205 was used in the 50MW Powerspan trial unit there for the FGD and WESP. This has been operating since 2004. Design chlorides were 10,000-15,000 ppm Cl. To my knowledge there have been no corrosion issues.

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.

http://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

 

[davefitz]

as a followup on concrete and rebar corrosion:

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.

 

[EdStainless]

The sulfates are the key. In straight Cl bearing water 2205 will struggle above 5,000ppm, but in scrubbers with high sulfate levels you can more than double the value. I have found enough references to usage in the 10-12,000ppm range to satisfy me that it works.

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Plymouth Tube

 

[robsalv]

So on the more broad question of direct Chloride resistance of 2205, does 2205's Cl- resistance increase with pH?

And following on from that, does Cl- resistance of series 300 stainless steel improve with increasing pH?


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