100% Iodine...Ouch ! ! !
100% Iodine...Ouch ! ! !
(OP)
I have a jacketed Inconel 625 vessel that we use to melt iodine pellets at 120F and 50 psig. The vessel wall has corroided from 1.25" to 1/2" in 10 years...ouch (75 mils/yr). We did an overlay 2 yrs ago and lost 0.300-inches.
We do not want to replace the vessel for 2 more years so must do some kind of repair/alternation.
Questions
#1 Is there a more suitable overlay we can do besides Inconel 625???
#2 We are also looking at sacrifical anoides. Inconel 600 came up but I think too close in galvanic series to be affective. What about Nickel 200. Galvanic potentials on Nickel Based Alloys isn't in just any text book... would Nace or NiDI have something??? Isn't there a ASTM test that can be performed to test various materials???
Thanks
We do not want to replace the vessel for 2 more years so must do some kind of repair/alternation.
Questions
#1 Is there a more suitable overlay we can do besides Inconel 625???
#2 We are also looking at sacrifical anoides. Inconel 600 came up but I think too close in galvanic series to be affective. What about Nickel 200. Galvanic potentials on Nickel Based Alloys isn't in just any text book... would Nace or NiDI have something??? Isn't there a ASTM test that can be performed to test various materials???
Thanks





RE: 100% Iodine...Ouch ! ! !
(assumes undiluted iodine)
Hastelloy C/C-276 1 apparently is excellent to 260 deg C.
Note same alloy does not fare as well with diluted iodine
Tantellum apparently is good to 149 deg. C
Excellent = <2 mils /year
Good =<20 mils /year
Vinyl ester apparently resistant to 65 deg. C
PTFE apparently resistant to 238 deg.
UHMWPE & HMW apparently resistant to 60 deg. C.
PET 120 apparently resistant to 120 deg. C.
FEP apparently resistant to 200 deg. C
Chemraz (FPM) apparently resistant to 200 deg C
RE: 100% Iodine...Ouch ! ! !
Use the same units for measuring (ins/mils/mm),& your loss rate numbers do not seem to compute.
You now appear to be losing 0.300 inches in two years. Whereas you lost .75ins in 10 years previously.
The crux is - what is the actual remaining thickness of the cladding left? From this you can estimate how much time you have left and can make your decisions based on that.
To rework the vessel means taking it out of service (I assume) and loss of production(?). Look at how long it was out of action when you did the re-work.
Initially it does not seem to be too bad to get 10 years out of the vessel. (what was the initial design life intended to be? I would think that it was designed with a corrosion allowance.)
From my long working experience, you will see on these pages that I often bang on that it is my view that we should cure the problem at source where we can and not rely on fixes to get us out of the mire.
I believe you should have looked at planning a replacement when you had 0.5ins (3+ years) left instead of doing the re-work. You would have had time to do so, look at new design and at least another ten years out of the new one. The only loss of production would have been changing one vessel out for the other. Now you are looking for another 'fix'
I suggest that you get back onto a planned maintenance / monitoring routine where you are in control, not the corrosion. Put some planning into place.
Do it now!
Find out the delivery and cost of a new one.
Design and order a new one with the design corrosion allowance / design life with the same materials, (or better, as suggested by Boomerang)if ten years is satisfactory and economic.
Depending on how much cladding you put on / have left, you may have six months or so left.
Monitor the corrosion of the existing one, get the new one delivered and replace it with the new one when most convenient from a production point of view (during a planed shut-down?).
Put into place a monitoring system on the new one, identify a minimum safe thickness (as designed) and when you reach you that (in ten years time say) order another new one.
Regards,
Quadswift
RE: 100% Iodine...Ouch ! ! !
RE: 100% Iodine...Ouch ! ! !
Are you just melting the iodine are vaporizing it?
RE: 100% Iodine...Ouch ! ! !
You bring up a very good point, liquid iodine has 0 conductivity...so that tells me sacrifical anoide won't work...right. What about impressed current on a vessel???
RE: 100% Iodine...Ouch ! ! !
RE: 100% Iodine...Ouch ! ! !
So our only options are a better overlay??? What about coatings???
RE: 100% Iodine...Ouch ! ! !
How big is this vessel?
RE: 100% Iodine...Ouch ! ! !
Maybe I'm a little obtuse, but Unclesyd and Metalguy brought up a point I'm still not 100% clear on... since the iodine (electrolyte) has zero conductance, I've inferred a sacrifical aniode won't work... right???
And I believe Metalguy nix'ed the impressed current idea...right??? Why???
RE: 100% Iodine...Ouch ! ! !
The only thing other than a corrosion resistant material of construction is some type of inhibitor to lower the rate.
What happens to the metallic ions(corrosion products)?