Have you ever wiped a vessel and found that the wipe had excessive black debris? This is common on mechanically polished vessels, especially when they have not been properly cleaned and prepped. This is often polishing debris from ground-in stainless steel particles and abrasive residue. Any comments on your experiences would be helpful!
 Daryl L. Roll, P.E.As Astro Pak's Chief Technology Officer, Mr. Roll serves as the primary senior technical advisor for corrosion, surface chemistry and stainless steel passivation. With over 30 years of experience in chemical processing, Daryl has been published in MICRO, UltraPure Water Journal and Chemical Engineering for his papers on passivation and rouge control. He is a participant on the ASME BPE Subcommittees for Surface Finish and Materials of Construction requirements and a leading contributor for the Rouge and Passivation Task Groups. Mr. Roll holds a B.A. in Chemistry and Earth Science from the California State University of Fullerton and a Professional Engineer's license from the State of California. |
|
||||||||||||||||
May 12th, 2009 at 9:36 am
We have a client that has supplied us with brand new stainless steel components for a pharmaceutical filling machine. The client has asked us to passivate the stainless in between every production run (nine cleanings and passivations). The product being run through the equipment is quite inoccuous and my question is - does repeating passivation this number of times have any positive or negative consequences or is it an exercise that will provide any benifits after the first passivation? Thanks.
May 12th, 2009 at 1:38 pm
With a relatively non-corrosive product or process, multiple passivation treatments will provide little or no benefit nor positive or negative consequences. Since passivation does not harm the surface or its finish, no damage would be incurred. The cleaning requirement is reasonable, but passivation would only be warranted if slight evidence of rouge formation was evident.
Thanks for the question, Daryl.
May 19th, 2011 at 3:05 pm
Can the same pickling and passivating procedures for Stainless Steel be used for Incoloy 800 pipe and fittings?
May 19th, 2011 at 6:52 pm
Donna:
Yes, the same processes used for typical 316 or 304 austenitic stainless steel can be used on Inconel 800 surfaces. The important condition for this and other high nickel chromium alloys, is that iron metal is not allowed to contaminate the surface. Weld damage or iron contamination would be reasons to pickle and passivate the surface of Inconel metals. The mill finish surface of this alloy is generally passive and corrosion resistant.
Thanks, Doc.
May 28th, 2011 at 4:37 am
We have a leakage problem with the Jacket of a jacketted vessel(200 L)
The vessel shell MOC is 1.4435 and the jacket is of ss304.The jacket drain line is slightly above the lowest point meaning some liquid always remains in the jacket all the time.We subject the vessel to SIP frequently.Sometimes it is allowed to cool naturally or putting air/processed water.
Recently we passed WFI through the Jacket after the SIP as we wanted to cool it down faster.That’s when we observed the leakage.
The leakage point is at the closure plate of the jacket which is welded and ground smooth.
THE VESSEL IS ONLY ONE YEAR OLD
Kindly give your opinion on:
1)Is this a stress corrosion cracking ?
2)Is it due to the fact that water has remained in the lowest portion for extended period of time?
3)Is this due to unfinished/unpolished part inside the jacket?
4)Is it due to fatigue due to sudden cooling via the jacket immediately after steaming
5)Is the crevice formed due to the closure plate welding at the bottom of the tank reason for this?
Please all also suggest the remedial action.
Thanks and Regards,
Kalyan
June 13th, 2011 at 2:54 pm
Kalyan,
In answer to your questions, my comments are as listed below:
1- This is likely stress corrosion cracking in combination with general corrosion.
2- Water remaining in the jacket stamnant and then during heat-up with steaming will directly stress the region.
3- The fact that the surface is “unfinished” will have little or no effect on the corrosion resistance, but if the jacket area was not passivated after welding, it would be very susceptable to corrosion.
4- Fatigue or stress induced by rapid cooling will also cause pre-mature stress cracking/failure and lead to higher corrosion.
5- If the closure plate is not at 90 degrees to the vessel wall and forms a crevice due to parallel plates, then this condition could also encourage cevice corrosion and stress cracking.
Chlorides in the cooling jacket fluids would also greatly increase the cracking potential of this area; steaming of chloride containing fluids will definitely induce chloride stress cracking and failure. In general, all of the conditions described above increase the likelyhood of crevice or corosion cracking due to stresses at the shell/jacket weld area. It is very likely that these factors have caused the jacketed area at the weld to fail and leak.
The remedial suggestions are as follows:
1- Inspect the weld area at the jacket shell interface. Visual cracking is likely present. Pressure test jacket for leakage areas.
2- Cut and grind Jacket weld area to expose the areas of failure; remove corrosion products, measure shell thickness and repair weld. Insure ability for drainage of all fluids from the jacket.
3- Derouge, Clean and Passivate the interior surfaces and exterior weld area of the jacket.
If I can be of further assistance, please contact us.
Doc.
July 5th, 2011 at 3:43 pm
We have recently purchased 132 new stainless 304 wine tanks. After cleaning we are finding a black residue on our white paper towels after rubbing on the polished areas and welds. can you offer a cleaning soluition?
Thanks
Eric
July 7th, 2011 at 11:11 am
Eric:
It is evident that the black residue needs to be removed by hand cleaning and wiping with an alkaline cleaner. These black (carbon) appearing residues are very fine particles of stainless steel and abrasives generated from mechanical polishing of welds and other flat surfaces. These surfaces need to cleaned, hot DI water rinsed and dried (2 to 3 cycles), then re-tested until surface will wipe relatively clean. Spray or immersion cleaning will not remove this well attached surface residue; it must be hand wiped with alkaline cleaner until clean.
I will send you a technical paper on our research that was done to identify the black residue often found on mechanically polished surfaces (weld or mill surface). This paper is also available on this website.
If I can be of further help, please feel free to contact me.
Thanks,
Doc.
August 18th, 2011 at 1:50 pm
If I passivate a 416, or 420 part then laser weld it (with shielding gas), am I compromising the passivation process by potentially allowing welding contamination that I want to stay corrosion free? I’m specifically referring to a 6mm x 4mm disk with conical interior and 6mm x 1mm disk laser welded to it.
Thanks!
August 18th, 2011 at 6:41 pm
Bob:
You will definitely need to passivate after laser welding. The weld destroys the passive film and compromises the corrosion resistance, even with gas shielding. The iron concentration at the surface increases significantly as the chromium vaporizes away at the weld area and in the heat effected zones. We see this same thing happen on laser etching of the surface, where the surface is not even melted significantly.
Thanks, Doc
May 24th, 2012 at 9:01 am
Mr. Roll,
We are suffering from a problem similar to this blog entry you posted dated July 7th, 2011 at 11:11 am in which you state
“It is evident that the black residue needs to be removed by hand cleaning and wiping with an alkaline cleaner. These black (carbon) appearing residues are very fine particles of stainless steel and abrasives generated from mechanical polishing of welds and other flat surfaces. These surfaces need to cleaned, hot DI water rinsed and dried (2 to 3 cycles), then re-tested until surface will wipe relatively clean. Spray or immersion cleaning will not remove this well attached surface residue; it must be hand wiped with alkaline cleaner until clean.
I will send you a technical paper on our research that was done to identify the black residue often found on mechanically polished surfaces (weld or mill surface). This paper is also available on this website.”
Is it possible to send me a copy of the technical paper you cited? Thank you.
Mohammad
June 1st, 2012 at 9:22 pm
Mohammad: The mechanical polishing residue can be difficult to remove and continue to re-appear for a significant period. Electropolishing is the best answer to the problem or wiping the surface with an alkaline cleaner. DR
November 19th, 2012 at 5:01 pm
Hi Doc
I have the same black issue and would be interested in have more info on your technical paper. Can you send me a copy please.
Also, I found many of your Technical papers interesting, but, was not able to read PDF4, PDF6 and PDF7. Can you also send them to me, it would greatly help me.
Thanks
Max
November 19th, 2012 at 5:31 pm
I will forward you the technical papers PF4,6 and 7, as well as the published technical paper on mechanical polishing of vessels (debris). Thank you for the interest in our technology and publications; i hope the information helps you with your issues and background support. Doc.
December 18th, 2012 at 3:12 pm
Mr. Roll,
Per your answer to a question of compromising the passivated stainless steel after laser welding, you stated that the person needs to passivate again. We do not not mind the need to passivate again for the welded area as we need to passivate the other non-welded region prior to laser welding. The chemical used in the passivation process may affect the material in other part of the sealed product when we do a full post-passivation. Do you have any knowledge on how the passivation will effect the hermeticity or strength of the laser-welded area? Thank you for your help.
January 14th, 2013 at 4:40 pm
Hi Doc,
Could I have a copy of the papers as well?
We are finding black residue after inspecting post passivation. It comes off on an IPA wipe, I was thinking it could be the mechanical polish issue, but our vessel was electropolished.
Any help will be greatly appreciated!
Thanks
Ben
January 25th, 2013 at 2:42 pm
Trung:
Passivation of the surface will not affect hermeticity (sealing ability of the surface) or strength of the laser weld, since passivation does not affect surface finish physcial properties. Passivation only affects 3 to 5 molecular layers which is not measureable in physical terms. Passivation of the weld heat affect zone is well documented as a need to maintain corrosion resistance. Welding greatly affects the corrosion resistance of the alloy and must be passivated in order to restore the surface corrosion resistance.
Hope this helps,
Doc.
January 25th, 2013 at 2:46 pm
Benjamin:
The black residue that you are finding, if the surface was well electropolished, may be surface debris from other sources. I would wipe the surface and have the wipe analysed for metal content and visually to see if the crystal structure of the compound can be determined. It could be carbon, rouge from steaming, microscopic stainless steel particles or a number of things. With an analysis, you should be able to determine the source and the respective remediation technique. But, likely the first thing to do is hand wipe the vessel with an alkaline cleaner and then see if the contamination re-appears.
I will send you the papers as requested.
Doc.
April 25th, 2013 at 8:25 am
Bill,
You can fill the vessel to processs and passivate, but this generates the most volume of waste. Generally we would recommend using a spraying device or spray ball to treat the surface and be able to use a 10% tank volume, reducing the process chemistry and waste volume. 2205 duplex steels can be passivated just like 304 or 316 stainless steels. The acceptable passivation process fluids are listed in ASTM A-967, and include either nitric acid solution at 25 to 40% depending on conditions of processing, or citric acid blends with chelants. The passivation can also be contracted to passivation service companies like Astro Pak. Doc.
April 29th, 2013 at 10:49 am
Bill,
Duplex 2205 passivates much like 304 or 316 stainless steels. You can use citric based chelant systems or nitric acid. Nitric acid is ,of course, a hazardous material and presents a hazardous waste problem. You can fill the vessels to treat the welds, but this greatly increases the waste handling problem. Spraying the vessels with a spray ball or orbital spraying device reduces the waste to only 10% of the vessel volume and actually performs a better treatment. you could also use a weld passivation paste and coat only the weld areas and then perform a deionized water rinse of the vessel. These are typical services performed by a passivation service contractor, like Astro Pak.
Doc