49458

Concentrated H2SO4 is stored in mild steel tank; what about condensation? [South Africa] 

July 25, 2008

Hi, I need to know what will the impact be of condensation in mild steel tank,
If I store 98% H2SO4 In a closed tank at outside temp ?

Jacques Viviers
Gm at Copper plant - Pretoria, South Africa

While you maintain concentration at 98% minimum, the H2SO4 will not attack the mild steel (it cannot act as an acid at that concentration). If water enters, it will ionise the H2SO4 allowing it to act as an acid and then it will very rapidly destroy the tank. The more water, the more ionisation, the more rapid the attack.

You refer to a "closed" tank - but surely it needs venting to accommodate normal atmospheric pressure changes as well as addition and removal of H2SO4? That would allow ingress of moisture-laden air, and the H2SO4 will immediately absorb any water from moisture-laden air.

Bill Reynolds    consultant metallurgist Ballarat, Victoria, Australia

Bill is right on this one. As soon as water comes into contact with the 98% H2SO4 it's going to dissolve your steel REALLY fast. You might want to use a container that isn't steel.

Jason Rothman
plating chemist - Pomona, CA, USA

Bill has hit the hammer on the head .. he's absolutely right.

M.S. is OK for storing conc. sulphuric but the ingress of air will dilute it and cause failure. Ditto for stainless, too.

Freeman Newton - White Rock, B.C. Canada

Hi again,

I forgot to say that the German Trovidur is supposed to be OK at 98% sulphuric ... and will scintillate for any lower concentration.

We used to make tanks from regular uPVC but methinks it was for 96% concentration.... this was for the battery business.

Yes and it was most definitely frp reinforced.

Freeman Newton - White Rock, B.C. Canada

Hi,

I am an Air Pollution Engineer who has done some work of this nature. MS is OK for 98% H2SO4. The fume frm the stored H2SO4 needs to be vented to a acid scrubber. It CANNOT and MUST NOT be totally closed! A provision for fresh air intake is necessary.

Leaking fumes will mix with the water in the air and try it damnedest to attack the MS from OUTSIDE. Thus the outside of the tank must be coated in at least 3 layers of FRP VE resin to prevent (or to delay) the corrosion process.

Sincerely,

Aaron ONG
- Ipoh, MALAYSIA