Coating a Stainless Steel Lab Reactor

[rollingstein]

We have a small lab reactor (~2 Litres) made of stainless steel that we use to test reactions.

Unfortunately, we now have one test which has a hot acidic environment (dil. HCl approx. 20%) that would corrode the native stainless steel.

Is there any way to work around this? Maybe a coating? I've heard of glass coated reactors but not sure if there's a way to do such a coating by myself?

Ideas?

 

[Mech_Engineer]

Time to buy a new reactor for the specific process you're interested in.

 

[rollingstein]

Time to buy a new reactor for the specific process you're interested in.

:) With barely 2 Litres of non-toxic (well, save the acid) material, I'm willing to improvise.

Not a huge risk. A new reactor is expensive. After all, the company must coat it someway too. If it's at all practical I want to do this homebrew.

Buying a squeaky, new off-the-shelf reactor every time I encounter a iffy material would be a expensive hobby. I'd prefer to explore other options (coatings, liners, passivation) first, if feasible.

PS. Lest anyone misunderstand, this is not a basement project. I've a decent lab with hoods, inert gas, steam, respirators and all the usual goodies.

 

[etudiant]

Coatings seem the logical option, provided you are sure you can remove them after the experiment and that they won't interfere with subsequent uses. Also, while HCl resistance is pretty easy, epoxy coatings will work just fine, hot HCl presumably means you are heating the vessel, which may be a problem for them.
Still, there are a plethora of coating material options and at the 2 liter scale, you could apply the stuff by hand.
Alternatively, could you perhaps just substitute a standard lab Pyrex vessel for the reactor?
Of course, if your reactor has complicated elements or serious pressure, then that is out, but that also would mean that coating might not be so easy.

 

[Graniar]

I suppose it's not that easy to cover it manually, if HCl would go through valves and etc.
What I would suggest, is to deposit protective film from vapor phase.
Ultimate long-term solution would be to heat thin platinum wire inside reactor in atmosphere of 10-100 Pa of inert gas.

 

[rollingstein]

What I would suggest, is to deposit protective film from vapor phase.
Ultimate long-term solution would be to heat thin platinum wire inside reactor in atmosphere of 10-100 Pa of inert gas.

How hot does the wire have to be? Pt must vaporize at fairly high T.

100 Pa sounds like a very low pressure of inerts, even if gauge pressure.

 

[rollingstein]

Coatings seem the logical option, provided you are sure you can remove them after the experiment and that they won't interfere with subsequent uses. Also, while HCl resistance is pretty easy, epoxy coatings will work just fine, hot HCl presumably means you are heating the vessel, which may be a problem for them.
Still, there are a plethora of coating material options and at the 2 liter scale, you could apply the stuff by hand.
Alternatively, could you perhaps just substitute a standard lab Pyrex vessel for the reactor?
Of course, if your reactor has complicated elements or serious pressure, then that is out, but that also would mean that coating might not be so easy.

Coatings seems indeed the best idea. Thanks.

I will explore to see what material works best.

 

[Graniar]

How hot does the wire have to be? Pt must vaporize at fairly high T.

100 Pa sounds like a very low pressure of inerts, even if gauge pressure.

Sorry, mean blowing very thin wire by capacitor discharge, not just heating. The inert gas pressure needed to make Pt atoms diffuse into shadowed parts of reactor instead of direct beam epitaxy like in high vacuum. And to avoid forming aerosol like it would be in higher pressure atmosphere.

 

[chemisttree]

Or you could just finely grind some pyrex and coat the interior with it while heating it to the pyrex melting point. Use a thin layer of waterglass Type N or T to make the pyrex flour adhere.