ระบบป้องกันการเป็นสนิมของเหล็กเสริมคอนกรีต และ เสาเข็มเหล็ก ขนาดเส้นผ่าศูนย์กลาง 800 ม.ม.ของโครงการก่อสร้างท่าเทียบเรือ A ด้วย ระบบจ่ายประจุไฟฟ้าขั้วลบ (Impressed Current Cathodic Protection, ICCP)
Created by GSG Systems http://www.gsgsystems.com for the US Department of Defense.
1) Could you explain our system ICCP working in brief?
Please refer to attached diagram for better explanation on ICCP system. Electron is flow from negative to positive terminal while current is flow from positive to negative terminal. The Mixed Metal Oxide (MMO) anode is function to inject current to piles (protect from corrosion) supply by the Transformer Rectifier (TR).
Note that, each terminal (anode and cathode) has their own chemical reaction which is involved Reduction Reaction (cathode or piles) and Oxidation Reaction (anode) which is naturally spontaneous to achieve natural equilibrium state.
However, because of the ICCP system is using Transformer Rectifier (TR) as the power source , the anode is not depleted/consume by time. The structure will be protected by the ICCP system as long as the TR is on to supply the power for the system.
2) In case of power outage, Are the piles still protected or not?
Or our system do have some battery or emergency power.
Or How long time The piles are still protected before power recovery?
Firstly, we need to understand what is polarization & depolarization of CP system. Polarization is where the potential of metallic structures are change due to potential different to achieve equilibrium potential and vice versa.
During installation of the CP system, in our case is ICCP system, the system need some time to polarize to achieve protection potential level (min -0.8V). The polarization event will take place several days (depend on the natural environment factor).
If the Transformer Rectifier (TR) is shut down, depolarization will occur which the potential of piles structure will naturally back to natural potential state. Same to polarization event, the depolarization also will need several days before it reach the natural potential which is prone to be corroded. This means that, we have several days (safety factor) to turn on the TR to protect the jetty piles from corrosion.
The backup power such as battery is not required if the power failure is only occurred for short time for temporary, as the corrosion is not an instantaneous reaction, immediately will cause the serious damaged on the pile. Corrosion is a slow process which take times to see the effect. With power off for few days, that will not really effect the pipe damage on corrosion.