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  1. runcyclexcski

    Removing smut and passivating a 304 welded part

    Not much information on the Iron III complex in the literature, but this 2023 paper describes it as a "black solid". Could have a blue color when diluted. Good absorbance at 318 nm, 515 nm, and 570 nm. https://pubs.acs.org/doi/10.1021/acsomega.3c00412
  2. runcyclexcski

    Removing smut and passivating a 304 welded part

    Ed -- i.e. if white H&S turns SS blue, it means SS not passivated properly? You got me really curious, so I am getting a bottle next time I go shopping. I suspect this might be the ingredient: https://en.wikipedia.org/wiki/Zinc_pyrithione The wiki lists it as anti-dandruff agent, and H&S...
  3. runcyclexcski

    Removing smut and passivating a 304 welded part

    >>> it was an automatic part of the offer they gave us to do the job. Exactly. When I buy, say, a custom-made sink in 304 to use in my kitchen, I expect it to work as is more or less out of the box, and not to have to dip it in a 200L tank of HF+HNO3. I did not ask the shop to pick the cost of...
  4. runcyclexcski

    Removing smut and passivating a 304 welded part

    Prometheus21 -- wow, hydrogen peroxide+H2SO4 (piranha) and 50% HNO3 are way beyond any DIY I can do at home. I am familiar with piranha from my biochemistry/biophysics work, any volume above 1 cup is bad news. Ditto on any ultrasonic/vibration devices. I did not expect SS 304 to be so tricky...
  5. runcyclexcski

    Removing smut and passivating a 304 welded part

    >>>You should have required that the part be cleaned before welding. You should be able to wipe with a white wipe and alcohol or acetone and see nearly no discoloration. A slight gray is no real issue. EdStainless: I did not expect to have to give specific instructions. I naiively assumed that...
  6. runcyclexcski

    Removing smut and passivating a 304 welded part

    Thank you for your response. I have already done the 10% NaOH myself, this had no effect (actually, the opposite -- it made the part shed more grey smutt). HNO3 you mentioned seems consistent with Dik's notes and the instructions from the manufacturer. In the mean time, I have received a...
  7. runcyclexcski

    Removing smut and passivating a 304 welded part

    >>>The percentages of acid were ordered; it was not hand mixed. Was it difficult to dipose of? I do not run a business yet, and ordering HNO3 and HF is prohibited in the EU by private individuals (in the USA the rules are a bit more relaxed, from what I understand). Thus, I am looking for a...
  8. runcyclexcski

    Removing smut and passivating a 304 welded part

    Many thanks, Dik, this was extremely helpful! And the 1976 paper I found is fully consistent with your notes. Sounds like nitric acid it is. I understand that your notes do not explicitly mention it, but -- was the acid purchased as 20%, or did you dilute yourself? Do you happen to recall the...
  9. runcyclexcski

    Removing smut and passivating a 304 welded part

    Thank you btrueblood. The piece has M4 tapped holes and corners that cannot be easily reached by mechanical scrubbing. I also have read that using "subpar-steel" brushes can cause even more damage. Not sure if this is true.
  10. runcyclexcski

    Removing smut and passivating a 304 welded part

    Hi all, I've been searching and posting all over the web about this issue. I apologize for the long question in advance. I had a 304 tray welded at a welding shop specializing in stainless and laser-cutting. The part is a box about 2' x 1' x 1' with 1.2 mm-thick steel walls (~0.05") and a...
  11. runcyclexcski

    Cellophane (regenerated cellulose) adhesive

    Hi all -- There was a thread on gluing cellophane (i.e. regenerated cellulose) to plastics here about 10 years ago. I've been trying to find adhesives for cellophane, but have failed so far. I am trying to make a small floatation device for dialysis which requires a leak-proof seal between an...
  12. runcyclexcski

    transparent analogue of PTFE or MACOR?

    I have yet another update on Halar/ECTFE behaviour in chloroform. After 18 hrs at 37C in Chloroform, it got swollen, and become rubbery. Transparency was still there. After I dried it off for several days, the rubbery consistency has remained, so it got affected irreversibly. So, although ECTFE...
  13. runcyclexcski

    acetone-resistant epoxy

    Great information, many thanks! It sounds like I am not ready to deal with aerosil, I will leave this to commercial manufacturers. Regarding amines: I myself used aminated glass (APTES-treated) to improve epoxy bonding... found this by accident, actually. After soaking with chloroform, the...
  14. runcyclexcski

    transparent analogue of PTFE or MACOR?

    Thank you! For ECTFEs, it appears that most of them are defined as 'translucent' (and appear as such in pictures), and only that Halar 453 stuff is defined as 'clear'. I beleive it's used in visors for hazmat helmets (acrylic/polycarb would be a problem, and glass might shatter). For my...
  15. runcyclexcski

    acetone-resistant epoxy

    Update: Epoxies etc recommend 20-3004 and "50-3182NC with Catalyst 30" for chemical resistance. Datasheets look quite impressive. The specs say they are resistant to conc H2SO4, conc NaOH, trichoroethane, and other solvents.
  16. runcyclexcski

    transparent analogue of PTFE or MACOR?

    I have an update on this, may be someone will find this useful. Folks at Laurel the spincoating company where kind enough to send me a cracked lid from one of their units, made from clear Halar 453 (according to Laurel). The material is 5 mm thick, and has the transparency/appearance of...
  17. runcyclexcski

    transparent analogue of PTFE or MACOR?

    I have dealt with small PFA tubes in fluidics (wall 0.5-1mm), they were cloudy/translucent. My application involves making a mechanically strong lid (say, 5 mm thick) to clamp down on a chamber, and I imagine at 5 mm thickness PFA would be pretty much non-transparent.
  18. runcyclexcski

    acetone-resistant epoxy

    Thank you epoxybot and ScottyUK. I will give the EP62-1BF product a try. I know MasterBond, it's just their products are not as 'of the shelf' as JB, but for this it's worth a try (and I do not need much epoxy, my optical mounts are only 2-3 inches in size). Are you suggesting that using a...
  19. runcyclexcski

    acetone-resistant epoxy

    Hi all, Has anyone have across 2-part epoxy which would not swell/fail upon long-term (ovenright) exposure of acetone? Chlorofrom-resistance would be even better, but I doubt it. We assemble water-resistant cuvettes out of glass pieces using 5-min and a UV-curable NOA-61 epoxy, which allows us...
  20. runcyclexcski

    cutting (cleanly) thin polypropylene sheets with double-sided adhesive

    berkshire, we have solved the problem by injection molding (for PP) and with machinning using glass instead of PP

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