% Oxygen Required for Corrosion

[klonteig]

I'm wondering if anyone has a good handle on how much (or how little) oxygen we would require in the following scenario to avoid corrsion of our uncoated carbon steel pipeline:

Fluid - sea water
Temp - 5 to 25 degrees C
Velocity in pipe - 1.4 m/s
Pressure - as high as 2000 kPa, as low as atmospheric

We're installing a de-aeration unit to prevent corrosion, but have no idea what level of oxygen is acceptable to avoid major corrosion.

Thanks!

Jordan

http://www.soltech.ca

 

[dcasto]

Any O2 will corrode. I'm not familiar with any equation that you could feed your data into and get an answer like 1.07 mils/year. I've run brine dearators and we pulled about 20" Hg to 25" Hgand didn't have any corrosion problems. I'd just plan on having a system to inject O2 scavenger chemicals based on corrosimeters or test coupons.

 

[SJones]

A rule of thumb limit to set is 20 ppb downstream of the deaerator to keep an 'acceptable' corrosion rate.

http://search.nace.org/query.html?s...w&ty2=w&tx0=water+injection&tx1=+oxygen&tx2=+

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/