With the current requirement for cold waters increasing to very high levels, coatings are becoming more attractive economically. The designer that substitutes coating for cathodic protection will also be required to make a decision regarding the effectiveness of the coating system with time as the coating ages. This figure is, at best, an estimate. There are little hard data that documents this condition and test data and experience is needed. In designing CP systems for deep water structures, anode material selection is one of the key questions.
More data is needed for anodes operating in typical deep water conditions.
This is the reason for initiating our current testing program. Goolsby 8 is specifying the use of an aluminum anode near the sea floor that contains 5 percent zinc instead of the usual 3 percent. This recommendation is based on a costly field testing program. The advantages of the higher zinc content should be examined further to see if it has proven merit under varying service conditions.