Corrosion mechanism of carbon steel under chlorinated H2SO4 service 3

[EVEN01]

Hi,

I've been going through the threads looking for information regarding the mechanism for corrosion of carbon steel piping under chlorinated sulfuric acid (98-96%) service. One of our spools failed (it had a hole in one side inside the pipe and the corrosion was uneven) and I'm trying to find some literature that helps me understand the mechanism under which this happens. Any leads on this? Thank you very much for your assistance

EVEN01

 

[rustbuster]

Even01,

Try

http://www.corrosionist.com/corrosion_protection_sulfuric_acid.htm

Was the line heat traced, if so it may be too hot.

Good luck

 

[EVEN01]

the line is not heat traced, and the temperature of the sulfuric acid is maintained at approximately 65-75 degrees F. Thanks for the link I will look it up.

 

[mggkg]

Refer to this data

 

[EVEN01]

thank you for the assistance!!

 

[ApC2Kp]

EVEN01,

The ability of carbon steel to resist sulfuric acid is result of the sulfate film corrosion product. As long as the flow velocity does not wipe off the sulfate film, then the corrosion rate is reasonably slow. The 65 to 75 deg F temperature has a slow permeation of acid through the sulfate film layer, so it could give years of life for a storage tank environment with little velocity to disturb the sulfate film.

A different situation occurs inside carbon steel piping with sulfuric acid flowing that removes the sulfate film. A flow velocity any higher than 2 feet/sec will result in shortened life of carbon steel piping in sulfuric acid service. Areas of turbulence such as elbows, tees, and control valve outlets will be first to corrode through the pipe wall. One remedy is to use stainless steel / Ni alloy spools at control valve reducers. The higher velocities allowed by stainless steel piping could be cost effective compared to the larger sizes of carbon steel piping needed to keep flow velocities to less than 2 ft/sec.