The cooling water for the LNG processing facility returns to the sea through pipes to a seawater outfall weir box reinforced concrete structure where it passes over a weir to a channel and back to the sea.
The water enters the outfall/discharge structure at high velocity and the resulting turbulence over the weir creates a large amount of seawater splash and spray over the internal as well as external portion of the side walls. The very humid environment created by the seawater spray is very corrosive. Chloride levels at the depth of reinforcement had exceeded threshold levels and reinforcement corrosion had started to cause cracks and delamination of the concrete cover.
Reinforcement corrosion study was conducted on the external surface of the walls in accordance with NACE SP 0308. Following the condition assessment it was decided to install an impressed current cathodic protection system to extend the life of the structure.
This paper describes the condition assessment and the tests required as per NACE SP0308 especially on the chloride content, cathodic protection design and installation of cathodic protection system during regular operations and particularly how the harsh conditions of the discharge structure were overcome to install, test and commission an effective corrosion control system.