PetroStreet

What if the cathodic protection of a hydrocarbon storage tank is compromised, and unavailable?
What should be the mitigations to be in place till a project activity is carried out to address the design /capacity deficiency?

If CP on an above-ground hydrocarbon storage tank (usually the soil-side tank bottom CP) is compromised/unavailable, treat it like a temporary loss of a key corrosion barrier.
Your goal until the design/capacity fix project is executed is:
Stop/slow corrosion acceleration,
Increase detection capability, and
Reduce consequence if a bottom leak happens.

There are certain things which you need to consider involving the inspection history of storage tank related to its bottom plat condition.
Any point in time, during the operation, has there been reported any issue with the bottom plate while CP was all good?
CP protection unavailability can actually call for an earlier inspection of the tank as well. So think around that when you perform detailed analysis.

Have you checked if there could be any temporary protection made available till you implement the full project.
To me this sounds critical where a hydrocarbon storage tank is left with no cathodic protection at all.
Temporary solutions may include provision of galvanic anodes. Or you can also consider installing portable rectifier is a temporary impressed current cathodic protection (ICCP) power source used to restore protective current until the permanent CP system is repaired or upgraded.
This approach is fully aligned with industry practice referenced in API 651 when CP is impaired and interim measures are required.
Check that out in detail.