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What is the best material to resist muriatic acid?

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by razor-edge-knives, Aug 9, 2019.

  1. razor-edge-knives

    razor-edge-knives Moderator Moderator Knifemaker / Craftsman / Service Provider

    Apr 3, 2011
    Need something that won't allow "bleeding" when soaking a blade in hot muriatic acid (160f). I've been using a paint enamel marker but it breaks down after a couple of minutes and I have to remove, clean, and reapply. Gets really old!
     
  2. 12345678910

    12345678910

    Jul 13, 2009
    Try nail polish
     
    razor-edge-knives likes this.
  3. razor-edge-knives

    razor-edge-knives Moderator Moderator Knifemaker / Craftsman / Service Provider

    Apr 3, 2011
    Thanks, I used to use nail polish before switching to the paint enamel but would still have issues although I have read all nail polish isn't the same... So if you have a specific recommendation then I'll snag some from Amazon! :)
     
  4. WValtakis

    WValtakis Hand Engraving, Anodizing and Embellishment Knifemaker / Craftsman / Service Provider

    May 29, 2004
    I usually have good results from the cheap obnoxious fluorescent colors...and as always, good surface prep (degreasing) is key.

    ~Chip
     
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  5. DevinT

    DevinT KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jan 29, 2010
    Someone told me to try rubber cement, haven’t tried it yet.

    Hoss
     
    razor-edge-knives likes this.
  6. bflying

    bflying Gold Member Gold Member

    Mar 4, 2014
    I've used rubber cement as a resist for anodizing. But the solution is not really caustic. I'd be interested to hear if it would hold up in acid.
     
    razor-edge-knives and DevinT like this.
  7. Natlek

    Natlek

    Jun 9, 2015
    Liquid Rubber ?
     
    razor-edge-knives likes this.
  8. bikerector

    bikerector Gold Member Gold Member

    Nov 16, 2016
    I've seen markers used for designing circuit boards. No idea if that would hold up to muriatic acid but as most of the solution is water and markers tend to resist water, dissolve with organic solvents, which HCl/Muriatic isn't, it could be okay.

    Didn't save the time tag, at about 0:35 they pull out the marker and then the rest is pretty much them drawing and dipping and then around the 3:15 mark you have the final result.
     
    BITEME and razor-edge-knives like this.
  9. bflying

    bflying Gold Member Gold Member

    Mar 4, 2014
    Yeah, sounds counterintuitive when I say it out loud also. Not being a chemist, was curious. Like how some acids can eat right through metal, but store just fine in a plastic bottle.
     
    razor-edge-knives likes this.
  10. bikerector

    bikerector Gold Member Gold Member

    Nov 16, 2016
    Reactivity, metals are dissolved by the ions of the acid, somewhat similar to how rust works, but plastic is impervious to most acids. It isn't too different than how plastic is used as an insulator in wires while the metal wire conducts electricity. Acids are essentially strong positively charge ions in solution, the H+ being the acidic part in HCl/Muriatic acid. OH- is generally the negative alternative in aqueous (water based) solutions.
     
    Jpgied, razor-edge-knives and bflying like this.
  11. ten-six

    ten-six

    119
    Mar 11, 2017
    Have you tried diluting the acid to see if it reduces the "creep" under the paint?
     
  12. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    Also, consider lowering the temperature of the acid. It will still etch, just slower. Hot acid is usually used to etch whole surfaces, not masked off surfaces.

    One thing you might try is High Temp porcelain/enamel paint for stoves and such. For small jobs, the touch-up bottles should work.
     
    razor-edge-knives likes this.
  13. Natlek

    Natlek

    Jun 9, 2015
    CA glue ?
     
  14. DevinT

    DevinT KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jan 29, 2010
    CA glue is not waterproof. Probably won’t work.

    Hoss
     
    razor-edge-knives likes this.
  15. Natlek

    Natlek

    Jun 9, 2015
    Not every one ............
     
    razor-edge-knives likes this.
  16. kuraki

    kuraki Fimbulvetr Knifeworks

    Jun 17, 2016
    I would try dielectric red insulating varnish. High adhesion up to 300+ degrees.
     
    razor-edge-knives likes this.
  17. razor-edge-knives

    razor-edge-knives Moderator Moderator Knifemaker / Craftsman / Service Provider

    Apr 3, 2011
    Ordered, at only $11 on Amazon why not lol
     
    kuraki likes this.
  18. Drew Riley

    Drew Riley

    Oct 17, 2007
    Why does the acid have to be so warm? Keeping it room temp would take a little longer, but it would certainly expand your options, I would think.
     
    razor-edge-knives likes this.
  19. razor-edge-knives

    razor-edge-knives Moderator Moderator Knifemaker / Craftsman / Service Provider

    Apr 3, 2011
    Yeah it comes down to speed, I could lower it a bit but I don't want to go all the way to room temp as that would take a while to get a deep etch on damasteel. I'm not sure if that would even help or not without experimenting. But I have 15 blades or so to etch so the quicker the better
     
  20. Cushing H.

    Cushing H. Gold Member Gold Member

    465
    Jun 3, 2019
    I wondered why the high temp also. You mght just be looking here at a fundamental trade off between time vs quality (not uncommon... )

    At a lower temperature the etching reaction will be much more predictable, and you will have FAR more options for resist (aspaltum/beeswax being the classic i guess). You could also possibly go with a photoresist if you need that level of quality. Agitation will help speed things up at lower temperature (and improve uniformilty). Best results (uniformity of etch) will be had at lower temperatures and continuous agitation) (i can explain the why behind that statement if you wish...)
     
    razor-edge-knives and WValtakis like this.

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