SS316 Compatibility on 10% NaOH Solution. 1

[Pavan Kumar]

Hi All,

I wanted to get hold of a reliable and verifiable source that gives the compatibility of SS316 material of construction for piping that will be used in 10% (w/V) NaOH solution. Can someone suggest a source that I cam refer to. My internet searches like the one below, have shown some charts but I am not sure if they are standard sources.

https://www.graco.com/content/dam/g...mpatibility-guide/Graco_ChemCompGuideEN-B.pdf

Thanks and Regards,
Pavan Kumar

 

[Latexman]

Maximum temperature?

Good Luck,
Latexman

 

[Pavan Kumar]

min temp is 50 Deg C and max is 90 Deg C

 

[jari001]

I've used charts from Graco and Cole Parmer before - reputable companies tend to have reasonably accurate information. For stainless steel specifically, I tend to look at metal specific companies/organizations (e.g.

https://bssa.org.uk/technical-help/)

for more specific information.

 

[Pavan Kumar]

Hi jari001,

Do you say that the the Chemical Compatibility charts by Graco or Cole Parmer are quite reliable?. From their chart I see SS316 is Good compatibility with 20% Caustic at 21 Deg C. Besides the Graco chart attached is for Pump material selection. Is this applicable for Piping Material selection too?. Where can I check the compatibility at 85 Deg C.

Thanks and Regards,
Pavan Kumar

 

[EdStainless]

https://secure.outokumpu.com/steelfinder/corrosion/

Why not use 304L?


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P.E. Metallurgy, consulting work welcomed

 

[Pavan Kumar]

Hi EdStainless,

Supra 316L/4404 is trade name for the SS316L pipe material sold by outokumpu?

Yes SS304L seems suitable and may be cheaper than SS316.

Thanks and Regards,
Pavan Kumar

 

[Latexman]

I agree with Ed.

Good Luck,
Latexman

 

[Pavan Kumar]

Hi Latexman,

Request you to explain how to read your chart please.

Thanks and Regards,
Pavan Kumar

 

[EdStainless]

That is a version of an isocorrosion diagram.
As long as you are under the line you are safe.
So with 10% you can run CS up to ~75C, 304 up to ~100C, and then other alloys above that.
One problem with CS in Caustic is the risk of cracking, at high temps it is also very flow sensitive.
There is also one on the Outokumpu corrosion data page.

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P.E. Metallurgy, consulting work welcomed

 

[Latexman]

Thanks, Ed. I went to answer, and my internet cut out on me.

Good Luck,
Latexman

 

[pierreick]

Hi,
Consider the resource underneath :

https://www.ssina.com/wp-content/uploads/2019/06/designguidelines.pdf

note : pay attention to the chloride content .
Pierre

 

[Pavan Kumar]

Hi Latexman,

Can I have a copy of the iso-corrosion diagram for Sodium Hydroxide you posted in your reply above. If there are pages which explain the diagram kindly post those too.

Thanks and Regards,

Pavan Kumar

 

[MJCronin]

For many years, the Caustic Soda Handbooks provided by DOW Chemical, OXY and PPG were the authoritative sources.

https://www.academia.edu/37847662/Caustic_Soda_Handbook_Dow

https://www.oxy.com/ourbusinesses/chemicals/products/documents/causticsoda/caustic.pdf

https://www.yumpu.com/en/document/read/11540376/caustic-soda-manual-ppg-industries

The technical publications and guidelines given by the "Nickle Institute" are also authoritative and superior to most others

http://www.xylenepower.com/nickelpub10019_causticsoda_20pg.pdf

Pavan, you must be aware that only a very modest increase in operating temperature for a short period of time can cause massive and immediate damage to very expensive caustic piping systems...

So .... if your butthole MBA boss tells Operations that there will be no problem if they run your system at 90C, be prepared for disaster

Tell us more about the details of your system.... have you selected pumps and valves yet ???



MJCronin
Sr. Process Engineer

 

[Pavan Kumar]

Hi MJCronin,

Thank you very much for providing the links to the documents. These will be very helpful to me.

The system that I am working is a Neutralization System which are improving now through a project. The plant I am working at has Neutralization system that is used to Neutralize all the acid waste streams(organic acids) in the plant that need to be neutralized before we send it to sewer. Attached with this message please find the System Sketch. The acidic streams are routed to a tank called " South Neutralization Tank" in which 50% Caustic Soda solution is added to bring the PH to 7. The addition rate of 50% Caustic soda is based on the difference between the set point PH and the actual PH. The neutralized water overflows to a second tank called "North neutralization Tank" where it gets more residence time to react. The stream then flows to the sewer where a final check on the PH is made. It was observed that there have been PH fluctuations and the water sewer sent to the sewer is remaining acidic. To increase the residence time we have proposed a recirculation system utilizing a spare tank called "IX Waste tank". The new recirculation Pump, piping is shown in red colour. Since the PH can vary anywhere between 2 and 14, the pump wetted parts, piping and valves have to be designed for both acidic and alkaline service. I have assumed the strength of Caustic soda after mixing with water to be 10% by weight. Hence checking the suitable material of construction for acidic service and 10% NaOH. The waste water normal temperature is 24 Deg C, max can be in extreme rare cases up to 65 Deg C.

We have chosen SS316 as the material for the pump wetted parts, piping and valves after checking the materials on the Cole-Parmer website "

https://www.coleparmer.com/Chemical-Resistance"

for acid and alkaline service compatibility. I also looked at the iso-corrosion diagram for Sodium Hydroxide for 10% strength. SS316 was found to be good up to 48 Deg C for our acidic service and for 10% Sodium Hydroxide hence made the selection. We will be purchasing the pump, piping and valves in a day or two.


Please let me know if you have comments and suggestions.

Thanks and Regards,
Pavan Kumar