[luckyhooked]

Hello all,
  I'm attempting to perform a KOH etch on a piece of steel in a large ultrasonic bath. The bath is new, so no fume hoods have been set up. Is it necessary to have a fume hood in place for an aqueous KOH solution at a temperature of no more than 50 degrees celsius? My understanding of the solution is that the only vapor it produces is water vapor, the KOH itself does not turn into a gas. In order to prove this and perform the etch sans fume hood I need to provide my safety guy with some sort of documentation to this effect. So far I have been unable to find anything that gives an indication one way or the other. Any suggestions?

[tamim83]

I don't think the KOH will etch the steel (or any metal) but it may clean it.  You should try using 30% formic acid, 30% hydrogen peroxide, and 40% DI water at 60 degrees celsius.  This is a scaled down etching process from "Handbook of electron tube and vacuum techniques" by Rosebury.  The actual procedure from the book is 45% formic acid, 45% hydrogen peroxide  and 10% DI water at 80 degrees Celsius.  These are percent by volume and the etching time should be around 2 minutes depending on how much you want to etch. 

As far as fume hoods go, you probably need some type of ventilation, but it does not need to be a fume hood, a well ventilated room should suffice.  One of the grad. students in my lab used the concentrated version recently on MO aperatures and did not use a fume hood and all was well. 

[luckyhooked]

Thanks for the response, yeah, I meant to say "clean" instead of "etch". Etching would be bad in this case. I'm glad you agree with me, do you have any idea where I could find documentation of the fact?