Difference between SS316L and SS316L Urea Grade

[Inspectengr]

Can you provide some reference to corrosion rate for 316L UG.

Arcpro: For 316L UG, the corrosion rate in huey test stands at 0.6 mm/year and for 316L it would be above this value.

To my knowledge, 316L UG has corrosion rate of 0.3 mm/year. (with reference to Heuy tests)
& 0.18 mm/year (25Cr-22Ni-2Mo)

these values are set by Snamprogetti specification for 316LUG and 25CR-22NI-2MO for their plants.

Ashfaq @ using 25-22-2 on 316L will really is not the cost effective option, but as u say can be directly used for 316L UG is alright...


Regards

[ashfaqanwer]

We used 25.22.2 on urea lines welds.
Unfortunately, the piping material and welds for Urea service at one of our plants is 316L (normal grade). Welds started to corrode due to high ferrite content against urea / carbamte solution. Piping has also suffered with corrosion. Replacement with Urea grade piping is being planned.
However in the last T/A, we selected 25.22.2 for re-welding of all the corroded welds as this is the perfect material for urea / carbamate.
And yes, for normal 316L not in urea service, 25.22.2 is not required.

[sakib321]

thanks for nice info my question related to it is that what differ between modified 316L and 25.22.2

[arcpro]

We procure 316L urea grade piping from Sandvik (product name: 3R60).
You can see their website for 3R60 and its corrosion rate evaluated by Huey Test.

Can you provide some reference to corrosion rate for 316L UG.

[arcpro]

316L modified (urea grade)
ASTM: S31603
Chemical Composition:
Cmax 0.02
Si 0.4
Mn 1.7
Pmax 0.015
Smax 0.010
Cr 17.5
Ni 14
Mo 2.6
1.Austenitic stainless steel (more pure form of 316L normal grade)
2. High resistance to ammonium carbamate
3. High resistance to intergranular corrosion
4. Good weldability
5. Corrosion rate stands at 0.6 mm / year (max.) as per Huey test

25.22.2
ASTM: S31050
Chemical Composition:
Cmax. 0.02
Simax. 0.4
Mn 1.7
Pmax. 0.015
Smax. 0.010
Cr 25
Ni 22
Mo 2.1
N 0.12
1. Higher grade austenitic stainless steel
2. Higher corrosion resistance in corrosive chemical process solutions like ammonium carbamate and nitric acid
3. High resistance to intergranular corrosion
4. High resistance to pitting and crevice corrosion
5. Good weldability
6. Corrosion rate stands at 0.18 mm / year. Sandvik 2RE69 guarantees max. corrosion rate at 0.12 mm / year

thanks for nice info my question related to it is that what differ between modified 316L and 25.22.2

[Nabeel Ahmed Qureshi]

With due respect One correction mechcolor. The carbon content in "L" grade is 0.03%.

[mechcolor]

O thanks, you are right.
I have edited the post.