Riboflavin not rinsing after Passivation on 316L 3

[PaulPro]

Good afternoon, All -
It'd be great if ANYBODY had a CLUE on what is happening to our product. We manufacture Spray Balls (Spray Lances, Spray Devices) for CIP Machines and other BPE equipment housings. Everybody in this industry knows that coverage testing is done with Riboflavin. Just recently we have run into an issue of Ribo not rinsing off the neck of the spray, also a 'halo' on the shoulder where the tube is welded to the spray ball top. On these devices, where the tubing is welded to the spray mounted ferrule, we have drain holes for self-rinsing of the tube. The Ribo is simple NOT rinsing off completely. What we know: This is NOT a coverage issue nor a lack of exposure to RO water. The entire lance is saturated after the 25PSI water bursts. This style of manufacturing has been performed MANY years with this design. Electropolish seems the help, a lot, and some may even say passes the Ribo test, but its green fluorescence is still ever so slightly visible after about 3 bursts of 30 seconds and then waiting for (5) minutes.
Can ANYBODY even point me in a direction of what would cause the Ribo to not rinse off of 316L? Again, this is NOT a coverage issue. This is actual BPE Riboflavin that is not rinsing off passivated 316L. Any help or direction would be greatly appreciated. Thank you.

 

[EdStainless]

It is related to the microscopic surface texture of the 316L.
Mills can supply just about whatever they want to as long as it looks right.
If this material was over-pickled at some point in process, then you stand no chance.
What are your surface finish requirements?
And don't tell me that it is based on Ra as this means nothing in your application.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[georgeverghese]

Is this what you are having a problem with - see slide 5 of presentation

https://esc4cip.com/wp-content/uploads/2020/07/Riboflavin-Solubility-SD4-2.pdf

 

[PaulPro]

@EdStainless -
I wanted to thank you for your reply. You were right in my ballpark for a suggestion. Thank you for taking the time! I believe you have a great point that this HAS to be the microscopic texture of the 316L. As of the date of my post we have got nowhere. Sending some samples to a lab for material testing is next. BUT, where in the heck and when the heck? No problems in years before this. I did check on the heat #'s for the 1-1/2" and the 1" that this is happening to and the supplier says it's one of their regulars. That doesn't mean it's still not a bad batch or been over pickled. Our surface finish requirements are simply mill finish. I don't know how to better answer that question. I will keep this post updated for the kindness you both (georgeverghese) have shown in taking the time. This is maddening.

@georgeverhese - Thank YOU also for your reply. You had a great suggestion on the Ribo prep and Solubility for coverage testing. We have done this several times with our Ribo to a 'T'. We even tried old Ribo and mixing it long for full dissolve at a slightly higher temperature in case we got a bad batch. So far, same results.

Current update: With the failed sprays, EP has worked with varying results. With new sprays, it appears to be working. The results are somewhat erratic with a couple of the spray devices rinsing quickly and showing no residual as we normally expect and others that show a “ring” at least reacting to the UV light at the neck. At times it is definitely very pale and blue rather than being discernable as green even after several minutes, which would still get flagged as a failure given the current situation. And others definitely show a green ring on the shoulder. As for the next steps, we are giving some samples to a testing lab to do some analysis on the material. This is to see if riboflavin can be confirmed as being present and causing the fluorescence or even the bluish luminescence that we see on some of them. This 'shoulder' is where the Tube welds to the ball top. It seems that the ball, from polishing, has somewhat of an undercut on the weld neck radius on the ball where one of the Ribo rings forms. While this is a polishing issue that can still be corrected, it would appear that the Ribo is still bleeding down TO this holding point.

And on we march. Thanks again to both of you!

 

[KernKraft]

@PaulPro
Hi, do you have anymore updates regarding your issue, such as the lab results of the material? I too am experiencing something similar during our commissioning process. Unfortuanately, it seems that there is a diluted stain of riboflavin where there were previous welds. Like you, there are no bright spots of riboflavin present. The tank that had rewelded work on the inner upper ring has been repassivated with no change. I would appreciate any advice at all