Protective Sheath System in the Splash and Tidal Zones of the Pilings
Pilings on piers, which are in a very corrosive environment such as sea water, are generally protected against corrosion by cathodic protection systems. However, this effective system to prevent galvanic corrosion, unfortunately, does not work in the areas of the piles that are most exposed to corrosion, splash and tidal zones. In this constantly chlorinated, wet and oxygen-rich environment, the damage caused by corrosion progresses rapidly to the levels that threaten the integrity of the structure. Cathodic protection is essentially a galvanic cell and works with the principle of forming anode and cathode of different potentials in the same electrolyte. Sacrificial anodes used in a perfect electrolyte such as sea water protect the steel surfaces against corrosion with the current they create on all surfaces under the water, but the system doesnt function in the splash and tidal zones outside the electrolyte. Therefore, special precautions are taken to protect the splash zones of the pilings and the corrosion is tried to be prevented with various sheath systems. Many sheath systems used physically protect the surfaces against external influences and aim to prevent corrosion by eliminating the contact of steel surfaces with oxygen. However, in chlorine-rich environments, these covers may also have the effect of increasing crevice and pitting corrosion.
Crevice and pitting corrosion, which progresses 10-100 times faster than normal corrosion, is mainly due to the fact that the iron dissolved in water in the oxygen-free environments under the passive film layer or any coating, attracts the chloride ions by charging positive electricity and the HCl forms inside, lowering environments pH down to 2, turning it into a strong acid solution.
These reactions, shown in the drawings above, explain the severe corrosion that occurs under many sheath systems. The SplashShield® protective sheath system developed to solve all these problems consists of a high physical, chemical and UV resistant, T-ribbed uPVC coating and e-Grout® that forms an alkaline electrolyte inside.
SplashShield® protective sheath system does not only constitute a physical protection and barrier like other alternatives, but also provides a chemical protection by providing a natural protective passive film layer on the steel surface with a very high alkali level such as pH 13.