98-99% Sulfuric Acid Tank (Material selection) 1

[Luike]

Dear colleagues:

Simillar to past thread related to 93%, i'm in a simillar case but with higher concentration. I must design a tank for this kind of content and i'm thinking to use standard carbon steel (A-516-60)as material. I was reading about their effect upon carbon steel and the explanation is the almost "passivating effect at low velocities", could anyone explain me better this matter or indicate me where I can obtained it.

Thanks in advanced for your inestimated help and efforts.

Best regards

Luike

 

[strider6]

In concentrated sulfuric acid a protective layer of oxydes develops on the carbon steel surfaces and prevent further corrosion. This if the fluid is still or moving at very low velocity. Increasing the velocity means that these oxydes will be removed due to erosion effect and following corrosion of new materials not protected by the oxydes.
this is a very simple explanation.. for further explanation i suggest you to look at shreir book on corrosion or hulig..

S.

Corrosion Protection & Corrosion Control

 

[Luike]

Thanks Strider6:

Basically, that's not the problem, at this hour, the point is determining which will be corrosion rate. Bibliography recommends between 0.13 to 0.5 mm/year, have you any expirience related to?. For to design , i assumed lower value because in a tank , i expect no higher velocities but
it is reasonably???

Thank again Strider6

 

[metengr]

I would suggest you make sure the sulfuric acid remains concentrated (> 93% by weight) with low velocity at nozzles. We have had carbon steel tanks corrode because of the ingress of moisture from damaged vents and excessive fluid flow at nozzles.


Some threads to review

thread124-141074
thread135-123720

among others....

 

[jistre]

Also, something to think about is that while sulfuric at those concentrations tends to not corrode CS, you have to be careful that you don't get moisture into the tank, no matter what the source. Sulfuric at lower concentrations will eat CS for breakfast. For example, if you get moist air over the sulfuric and the liquid level in the tank tends to stay in a pretty narrow range, you can get localized corrosion at the air/acid interface because the same area is constantly under attack due to the moisture of the air combining with the sulfuric.

As a side thought, if your tank is small enough, is plastic an option for the tank? It should be cheaper and easier than a steel tank if it's acceptable.

 

[jistre]

I see that metengr said what I was typing as I typed it.

 

[strider6]

i've seen some pipe and tanks with corrosion at the interface as jistre said.
carbon steel is noramlly used for high concentrated sulfuric acid and the reference i've is that the velocity should be lower than 0.9 m/s or 3 ft/s. For higher velocity, pumps for example is necessary to use corrosion resistant alloys.
Regarding the corrosion rate there are isocorrosion curve for carbon steel and the range normally is 0.15 to 1.0 mm/yr but is very denpendent on velocity , temperature.....
these reference can guive u some good advice on materials selection for Sulfuric Acid.

http://www.sulphuric-acid.com/TechManual/Storage/storagetanks.htm#Corrosion

http://www.genchemcorp.com/pdf/tsr5078.pdf

http://www2.dupont.com/Clean_Technologies/en_US/assets/downloads/Equipment_FAQs.pdf

hope this help u

S.





Corrosion Protection & Corrosion Control

 

[strider6]

this is another good one...

http://www.norfalco.com/safety/storage_tanks.htm

http://www.norfalco.com/documents/NorFalco_H2SO4TechBrochure.pdf

S.

Corrosion Protection & Corrosion Control

 

[Luike]

Dear strider6:

I'm very surprised for your promptly help in this matter, really thanks for your effort. At this moment your info is totally enough for to finish this job.

Thanks to rest of colleagues .

Luike

 

[strider6]

i'm working on a website (

http://www.corrosionist.com)

with all the useful informations on the web on corrosion, corrosion control.. (maybe not everything..) it's a work in progress..
one of the tools in my website is a Corrosion Search Engine based on a tool of Google that allow you to define the sites where make searches so to have more targeted resuslts.. now it contains approx 250 website.. it can be useful as in this case...
feel free to suggest sites that you think should be included..

S.

Corrosion Protection & Corrosion Control