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Request advice on right application of NaOH or KOH

  1. Sep 16, 2004 #1
    I work in a restauant and use KOH and NaOH as degreasers. Will these damage our septic system if I put them down the drain? Would it be better to send them to the landfill? Is one less harmful to the environment than the other?

    Personally I use them as spareingly as possible but I know other workers use them without restraint. Am I just being fussy or is there a good reason to try to minimize the amount used? If there is a good reason to minimize, is there a resource I can use to try to convince my co-workers to be more conservative?

    Thanks for any information

  2. jcsd
  3. Sep 16, 2004 #2


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    I've got no practical experience in this area, but nevertheless, from a theoretical point of view, here's my five cents worth :

    A little bit (much is a little ? ~ 200 ppm) of NaOH/KOH is good, from a corrosion point of view. However, too much (how much ? I don't remember the numbers for this) alkalinity will lead to Caustic Embrittlement (aka Stress Corrosion Cracking) of metal (typically iron/steel) pipes.

    I don't know much about environmental effects.
  4. Sep 16, 2004 #3


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    Do you use solid NaOH/KOH? If you use a solution, then it is probably okay to put down the drain with a lot of water, if you use the solid, I would dilute it with a lot of water first.
  5. Sep 17, 2004 #4
    Thanks for the thoughts. I didn't know that about caustic embrittlement. The cleaning product comes in gallon bottles, is a liquid, and does not state the ppm. I do dilute it and wash it down with lots of water. Our plumbing is all plastic, as far as I know. The building is new, only a few years old. But we have had trouble with the septic.

    I dilute the product to about 1:64 for general cleaning, but use it full strength (according to directions) on our nickle grill. I sometimes use it on the stainless steel walls behind the cook line. Does caustic embrittlement affect stainless? It takes the grease off but I don't want to dull the finish.

    I do use a solid NaOH product for cleaning out the deep fryer. It is dissolved at about two cups to fifteen gallons of water. After boiling for an hour, I drain the stuff into a mop bucket and use it on the quarry tile floors. It cleans up the grout lines like nothing else I have tried. I have also used it to clean stainless steel vent covers. I have found it to be a bad idea to use it on aluminum or on white metal, as it corrodes those and off-gasses what I presume to be hydrogen gas. No, I havn't tried lighting a match to it.

    By the way, the KOH product carries a warning label with the number two under flammability. It doesn't contain any alcohol or organic solvents, so I suppose this has to do with the hydrogen.

    Anyway thanks for taking some time in applied science.

  6. Sep 20, 2004 #5


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    That flammability thing is odd. KOH and NaOH aren't really flammable, so it must be something else that is added in there as well. Be really careful when washing floors with that KOH mixture, base solutions tend to be very slippery, especially one as concentrated as that.

    From my experience using KOH solutions to clean glassware, you would have to leave the stuff in the base solution for a considerable time before you saw any ill effects. I don't have much experience with cleaning metal surfaces this way though. Regardless, I think that the corrosion reaction is relatively slow, so as long as you rinse everything thoroughly and don't let it sit overnight or anything, you should be fine.
  7. Sep 20, 2004 #6


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    The number two under flammability probably discusses the ill effects of KOH with amphoteric metal surfaces like aluminum; as you tried and saw, hydrogen gas evolution along with a considerable corrosion may be present on these surfaces.

    Regards, chem_tr
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