Why do chemists use Nitrogen in their safety boxes?

[zpepelepu]

Interesting discussion, perhaps my question could be answered:

Would nitrogen be reactive in any way in a production process involving an inline pickle (descaler/oxid removal)? The process involves maintaining an aquaeous acidic bath, usually involving 10% concentration hydrochloric acid at 140 deg F, in a spray impingement stage, used on hot rolled steel to remove the oxide formed from laser cutting.

Please no speculation, just the straight dope, thanks.

[asterion]

That’s really a chemical engineer or experienced process chemist question. I think we’ve got a Chem E or two around (Nava is one, I believe) but I don’t know if we’ve got any old-timers on the process side. You might get a good answer if you ask the OPRD group on LinkedIn.

[am77494]

@zpepelepu

Would nitrogen be reactive in any way in a production process involving an inline pickle (descaler/oxid removal)?

ChemE here. Nitrogen as an element is as effective in this application as Argon (the only other benefit with Argon is that is heavier than air and tends to settle down). What you need to to think about is whether your process has a potential of generating Hydrogen gas - that is metal reacting with acid.

If you do have that potential - then you need to think about the purity of Nitrogen (or Argon ) that you are going to use to make sure your system is safe. (You do not want the small percentage of Oxygen in your inert reacting with the H2 generated, if any).

The second thing you need to think about is the purge or sweep rate - to make sure that you are flowing enough inert to “sweep” away the “fumes” that you are generating at a safe rate.

The third and the most important thing you need to think about is that you have a safe and permitted way of disposing the inert once it leaves your system. From your description, this does not sound like a laboratory - so you will have industrial and environmental laws to follow for disposing the inert once you are done.

[zpepelepu]

Permitting for nitrogen evacuation should be a nonissue. Pretreatment systems have stacks on each end/within, with active exhausting which includes steam/vapor from alkaline cleaners, zinc phosphate, acid pickles and non-chrome sealers, the main purpose being to maintain balance in the stages to prevent cross-contamination.
Similarly, H2 is generated in electrocoat tanks but there is no danger of accumulation/saturation.

Appreciate the feedback.

[standingwave]

@am77494

ChemE here. Nitrogen as an element is as effective in this application as Argon (the only other benefit with Argon is that is heavier than air and tends to settle down). What you need to to think about is whether your process has a potential of generating Hydrogen gas - that is metal reacting with acid.

If you do have that potential - then you need to think about the purity of Nitrogen (or Argon ) that you are going to use to make sure your system is safe. (You do not want the small percentage of Oxygen in your inert reacting with the H2 generated, if any).

The second thing you need to think about is the purge or sweep rate - to make sure that you are flowing enough inert to “sweep” away the “fumes” that you are generating at a safe rate.

The third and the most important thing you need to think about is that you have a safe and permitted way of disposing the inert once it leaves your system. From your description, this does not sound like a laboratory - so you will have industrial and environmental laws to follow for disposing the inert once you are done.

I really want to watch Breaking Bad with this person.