11 – Low-voltage aluminium anodes – optimization of the insert–anode bond

Publisher Summary This chapter mentions that Delegation Generale pour l' Armement (DGA) and DCN have developed a new Al–Ga low voltage anode that is in use to protect marine structures. After the development of the first industrial anode version with plain rod inserts, additional studies were launched with the aim of optimizing the insert–anode bond. Some of the conclusions drawn from both laboratory studies and field experience are: (1) Use of plain rods as inserts has proved to be unsatisfactory as penetration of seawater at the insert–anode interface occurs, thus reducing the performance of the cathodic protection system. All the attempts regarding modification of the insert surface preparation, nature or geometry did not improve the behavior of such anodes used in severe cyclic pressure conditions. (2) Although expensive, treating the anodes with plain inserts by Hot Isostatic Pressure could be a promising orientation. However, more tests are necessary to reach a final conclusion. (3) A new anode design with stainless steel fittings replacing the insert was developed, qualified, and installed on a new marine structure. Adequate continuity between the anode and the structure to be protected was achieved; thus ensuring a good protection level. If this option has proved to be an efficient one, it is, however, a costly solution. (4) Laboratory tests have shown that the use of tube inserts is a promising option. Further investigations on Al–Ga industrial versions as well as supplier qualification are necessary before any use in service.