corrosion in c02 piping

[sdennisf]

I have a customer that uses our canned motor pumps in their C02 refrigeration systems between o and +20F. He has asked if we are aware of any corrosion problems in steel or copper piping. I am not aware of any problems but thought I would check to see if anyone has experienced any corrosion problems with refrigeration grade c02.

 

[rodneybennet]

Is there any indication of the amount of moisture present in the CO2?

Note that a - basically - similar thread was started at

http://www.composite-agency.com/materials-forum.htm,

specifically:

http://www.composite-agency.com/messages/4758.html

Regards,
Rodney Bennet

 

[sdennisf]

Rodney,
No moisture. Any moisture would be ice in these systems. Thanks for the links to previous posts.
Denny Fegan

 

[0707]

Carbon dioxide (CO2) corrosion results when CO2 dissolves in water to form carbonic acid (H2CO3). The acid may lower the pH and sufficient quantities may promote general corrosion and/or pitting corrosion of carbon steel.

Affected Materials: Carbon steel and low alloy steels.

Prevention / Mitigation:

Corrosion inhibitors can reduce corrosion in steam condensate systems. Vapor phase inhibitors may be required to protect against condensing vapors.

Increasing condensate pH above 6 can reduce corrosion in steam condensate systems.

The 300 Series SS are highly resistant to corrosion in most applications. Selective upgrading to stainless steels is usually required in operating units designed to produce and/or remove CO2 (such as hydrogen plants and CO2 removal units).

Steam condensate systems that experience CO2 problems are usually the result of operating problems.

400 Series SS and duplex SS are also resistant.


LM

 

[zdas04]

There are several CO2 corrosion modalities, but they all require the gas to be disolved in an electrolyte. If the CO2 is dry and no pooling liquids are present then your internal corrosion risk is nil.

David