Asphal and Impressed CP of tank

[fouad20011]

Dear All,
I will wondered if someone can explain me how a cushion of asphal installed under button tank can affect impressed current CP.
I use impressed CP to protect the outside butom thank, but i am affred because there's no way to the current to follow trought tank since the are a cushion Asphalt .

Regards!

 

[SJones]

API RP 651

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[brimmer]

A little late in responding but the resistivity of the asphalt will certainly be higher than the soil, and it will be more difficult (but not impossible) to push current through, thus requiring such a high current demand CP may not be practical. This may or may not be the case for your situation, depends on composition/condition of your asphalt, and diameter of the tanks. You should be able to see if the CP is having any affect by taking a native soil potential after tank has depolarized, and potenetial with current applied. Was there a difference? Typically you would use the 100mV criteria on tanks for protection.