Anodes and impressed current on submarine pipeline?

[jcook14]

Hi,
I am green in the area of cathodic protection so I am hoping for any helpful advice

Background - Our marine pipeline is Mild Steel Cement Lined (MSCL) with a diameter of approx 1200mm which is 3.7km long. The MSCL pipe will have a 2.3mm thick fusion-bonded coating. The pipe is to be installed via the bottom-pull method and will require a concrete weight coat of approx 100mm.

The cathodic design has been completed for an impressed current system. Due to the isolated area, the cathodic protection system also allows for anode protection for the first 12 months, to allow time for the impressed current system to get a power supply and be commissioned.

The client is now requesting anodes in addition to the impressed current system for the full life of the pipeline (100 years) because they have it on other pipelines. Apart from the commercial side of it, is there a technical reason why this should not be done? That is, can anodes and impressed current provide protection at the same time?

From what I can find so far, the impressed current system will simply run at a very low current.

 

[SJones]

For a 100 year life there will be more anode than concrete! If the impressed current system has been designed correctly and the pipeline installed correctly, there should not be a need to double up when the IC system is energised.

Steve Jones
Materials & Corrosion Engineer

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

 

[mshimko]

My experience is more with vessels than pipelines, but the principles are the same even if certain conditions are not.

IMO, the ICCP system if not designed properly if it needs to be supplemented with sacrificial anodes (unless you intentionally under-designed the ICCP system). That said, I see nothing technically wrong with using sacrifical anodes along with an ICCP system, as long as you are aware of both when you do the calculations, take readings, make adjustments, etc.