Corrosion Threshold of Different Stainless Steel Types
Corrosion Threshold of Different Stainless Steel Types
(OP)
Does anybody know of a good resources that discusses corrosion threshold limits? The application that I am using it for is service life modeling of different reinforced concrete structures in marine environments.
I am particularly interested in the following types of stainless steel:
2205
316LN
2101
2304
304(LN)
In order to model this in a service life program I need the actual threshold values based on the ASTM testing method.
I am particularly interested in the following types of stainless steel:
2205
316LN
2101
2304
304(LN)
In order to model this in a service life program I need the actual threshold values based on the ASTM testing method.
RE: Corrosion Threshold of Different Stainless Steel Types
RE: Corrosion Threshold of Different Stainless Steel Types
Lots of that published, and even some that show shifts with temp, pH, and Cl concentration.
https://res.cloudinary.com/engineering-com/raw/upload/v1602262489/tips/pitting_curves_pu1rpx.docx
or this
https://res.cloudinary.com/engineering-com/raw/upload/v1602262691/tips/CCT_chart_fjgu05.docx
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P.E. Metallurgy, consulting work welcomed
RE: Corrosion Threshold of Different Stainless Steel Types
Cheers
GG
RE: Corrosion Threshold of Different Stainless Steel Types
(EDIT: You beat me to the response)
GGedge... Chloride Corrosion Threshold (to my understanding) is the threshold limit in ppm of chloride concentration to initiate corrosion of the steel. The testing that I have seen done to measure this (I'm sure there is more than one way) is to cast concrete minibeams reinforced with rebar. They then will then flex the minibeam to crack it on the cover layer. They pond a 3% NaCl solution on the top of the minibeam and cycle it with a wet and dry time. They then crack open the minibeam and measure the chloride levels and observe the level of corrosion. From that they can deduce the chloride threshold level.
EdStainless.... Thank you! I took a look at the graphs. The pH is important since the service life modeling that I am interested in deals with steel cast in concrete. So looking for a pH environment around 12. That is interesting to see the regression line that is the function of Cr, Mo, and N. Both of those graphs that you sent me show 316 stainless steel to have a threshold limit of below 500 ppm at neutral pH and ambient temperature. I am curious to what it would be at a pH of 12 or 13. The research I have found on 316 stainless steel embedded in concrete has a chloride threshold limit of around 4750 ppm. Does that sound correct?
RE: Corrosion Threshold of Different Stainless Steel Types
Cheers
GG
RE: Corrosion Threshold of Different Stainless Steel Types
There is also the issue of other corrosive species, such as chloramines. These are volatile Cl containing organic compounds that can cause CSCC in SS at near ambient temps (look up history of collapse of concrete swimming pool roofs).
As far as bang for the buck goes you can't beat 2101. It is at least as pitting resistant as 316, it is much more cracking resistant, and it is much stronger (use less metal).
At higher pH and low temps (in liquid caustic) I would trust 316 at higher Cl levels, but in an environment like yours you need to think about worse case conditions.
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P.E. Metallurgy, consulting work welcomed
RE: Corrosion Threshold of Different Stainless Steel Types
Cheers
GG
RE: Corrosion Threshold of Different Stainless Steel Types
I will have to read up on chloramines as I am not familiar with that.
GGedge, you are correct! This is for service life modeling based on Fick's Second Law of diffusion. Considers only chloride diffusion in a perfect uncracked concrete scenario. Definitely, unrealistic, but seems to be the industry standard. On a side note, I am changing the parameters in Life365 (i.e. the chloride exposure, concrete diffusion coefficient, chloride threshold, and propagation period). I have lots of great information concerning different admixtures and types of rebar and how to manually modify the inputs but currently Outokumpo has not been very helpful to me in supplying some of the test information I had requested from them. Do you know of another service life modelling program other than Life365 for reinforced concrete? I was told that there was another one that was going to be coming out of the UAE and would be able to account for sulfates and cracked concrete conditions. Thanks for the lead on Pedeferri/Bertolinni.
Your memory of it being an order of magnitude higher seems to be spot on! Black Bar threshold is 0.0005% and 316 stainless steel is at 0.0048% according to Life365 and many other independent sources.
RE: Corrosion Threshold of Different Stainless Steel Types
The only reason I can think of for using 2205 reinforcement are commercial, it might be more economic than the 316 and derivatives. For practical purposes with typical design lives (say 50 to 120 years) durability will be similar unless you are looking at crazy long life (hundreds of years). Our standard specification, for stainless steel reinforcement on structures in a splash zone, is 1.4307 (304L) or 1.4162 (2101) for 120 year life; the choice is usually a commercial one for the supply chain. The grade might get bumped up in very hot climates, for example the Middle East. There might also be a case for areas with de-icing salt on bridges without waterproofing.
Assuming the reinforcement is produced to a recognized standard, ASTM A955 or BS6744, all the alloy grades will need to meet a common strength grade to comply. In Europe that is 500 MPa, I think the ASTM is similar but with some lower strength options.
Chloroamine is a problem related to the particular environments created in swimming pool hall atmospheres (not in the water itself). It is interesting to know about generally but is not something to worry about for stainless reinforcement in concrete in marine environments.
CHeers
GG
RE: Corrosion Threshold of Different Stainless Steel Types
That said if I was doing a bridge I would look at 2205, andy other marine structure and 2101 would be my choice.
As a family the duplex grades are more resistant to CSCC than the austenitic grades.
I guess that the cases that I have been drug into have been unusual then. The ones that I have seen have had extensive carbonation and were more permeable than they should have been.
I have also seen tidal environments where chloramine generation was detected and blamed for ambient temp CSCC in 316L.
It would figure that I have only been involved in some weird cases, sorry for generalizing.
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P.E. Metallurgy, consulting work welcomed
RE: Corrosion Threshold of Different Stainless Steel Types
"I guess that the cases that I have been drug into have been unusual then. The ones that I have seen have had extensive carbonation and were more permeable than they should have been.""I
is that referring to stainless steel or carbon steel reinforcement?
"I have also seen tidal environments where chloramine generation was detected and blamed for ambient temp CSCC in 316L."
Likewise was that CSCC of 316L Reinforcement in concrete?
RE: Corrosion Threshold of Different Stainless Steel Types
RE: Corrosion Threshold of Different Stainless Steel Types
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P.E. Metallurgy, consulting work welcomed
RE: Corrosion Threshold of Different Stainless Steel Types
Cheers
GG
RE: Corrosion Threshold of Different Stainless Steel Types
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P.E. Metallurgy, consulting work welcomed
RE: Corrosion Threshold of Different Stainless Steel Types
Ed, do you have a reference or soruce for those 2 files/figures? I found them incredibly useful in a general sense, and like to use them for my personal dossier.
Huub
- You never get what you expect, you only get what you inspect.
RE: Corrosion Threshold of Different Stainless Steel Types
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P.E. Metallurgy, consulting work welcomed
RE: Corrosion Threshold of Different Stainless Steel Types
Huub
- You never get what you expect, you only get what you inspect.