Cathodic protection design of high voltage tower in offshore for 20 years service life

High voltage tower structure used as the object of research for the SACP design uses one of the PLN high voltage tower with type BB6+3M SLIM with a total height of 38 meters. Due to its location in the marine environment (offshore), this tower is divided into 3 zones, namely the atmospheric zone with a height of 31 meters, a splash zone with a height of 2 meters and a submerged zone with a height of 5 meters. The atmospheric zone will use corrosion protection with the coating method, while the splash zone and submerged zone will use a combination of the coating method with sacrificial anode cathodic protection (SACP). The data used in this study were obtained both from field data, and data from literature. The current density value for this study was used 150 mA/m2 for the initial conditions, 70 mA/m2 for the mean conditions and 100 mA/m2 for the final conditions (DNV-RP-B401, 2017). The area to be cathodically protected includes the splash zone and the submerged zone with a surface area of 22.45 m2 for the splash zone and 56.12 m2 for the submerged zone. The value of paint damage factor and current density follows the recommendations of the international standard DNV-RP- B401. The results of SACP design for offshore high-tension tower with a service life of 20 years require 4 anodes of Al- Zn-In alloy type with a capacity of 2464 (A.hr/kg) and weight of each anode is 50 kg. The chosen protective coating combination is a category III epoxy coat with two or more layers of epoxy, polyurethane or vinyl-based marine paint, with a total OFT 350 µm.