1. OFFSHORE STRUCTURES

The three basic options for cathodic protecting offshore structures; namely impressed current or sacrificial anodes protecting a bare metal structure or sacrificial anodes on a totally protecting a bare metal structure or sacrificial anodes on a totally painted structure.

There are three basic options for cathodic protection (CP) of offshore structures; namely:-

Bare steel structures protected by impressed current (IC) systems.

Bare steel structures protected by sacrificial anodes.

Painted, steel structures protected by sacrificial anodes.

Each method has its merits, but against these should be set the problems that can arise, and in some cases these considerably outweigh any advantages that the systems may appear to have at the design stage.

Whatever system is opted for it should be designed to give steel potentials and current densities in accordance with Tables 2 and 3.

Consideration of possible problems at design stage is essential, a underwater repair costs can be as much as ten times the cost of the whole of the original installation.

Sometimes the choice of CP system is influenced by weight limitations, especially if barge launching of the structure is being considered.

Application of Cathodic Protection for offshore structures are as follows:

1. The submerged and buried steel work of the jacket of an offshore platform

2. The columns or legs of jack up drilling rigs.

3. Wharves or jetties steel piles

4. Ship Hull.