Internal CP for a Jet Fuel tank 2

[brpillai]

I am designing a jet fuel tank. It requires internal cathodic protection as per the client.The tank is internal floating roof type, having an aluminium roof over the floating roof. The Interla CP is to prevent corrosion from the very unlikely occurance of water inside. Tank and the product is suppoesed to be free of water, and a regular check and water draining and sampling facility is included in the design. It will have CP for below bottom plate prtection. My query is about the tank internal protection.

I have the following queries.

1. Is Impressed current CP is feasible for internalprotection of Petroleum storage tanks. The issue I find is the cable connection on the inside surface. are there any other concern on the safety for the cable taking inside.
2. As there are chances of water present ibside, if SACP is the selected option, I understand that Aluminium anode is the choice. However, for aviation fuels, Aluminium is not allowed to come in to contact with fuel, as it would contaminate the fuel.

I would like to know from the experts, your suggestions.

 

[SJones]

If there is no water then a) there is no corrosion, and b) there is no electrolyte to conduct cathodic protection current. A jet fuel qualified coating would be the secondary corrosion control measure, after the primary one of operational water drainage, principally to minimise rust contamination rather than act as an ultra reliable barrier to perforation. A further consideration is the type of water expected in the fuel. Simple vapour condensate will not be sufficiently conductive to operate aluminium sacrificial anodes. The anodes will also require a stand off distance from the tank surface which may be more than the expected depth of water, thus they will simply sit in fuel and not function anyway.

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.

 

[brpillai]

Steve Jones, Thanks for the advice. Have you come across any internal corrosion protection for jet fuel tanks? Here the client is insisting to have. As you rightly said, the anodes will not work in traces of water. I am trying to convince the client that it is not required.

However, my second question is not answered. Whether impressed current CP is feasible for internal protection. How will the cable be taken to connect to the anodes inside?

Expecting your advice.
Thanks and regards
Bhaskaran Pillai