Accelerated Low Water Corrosion (ALWC) is a particularly aggressive form of microbiologically-induced localised corrosion affecting steel piling and other brackish or sea water immersed structures, which is most commonly found close to the level of the Lowest Astronomical Tide (LAT).
To mitigate this, Cathodic Protection (CP) and/or coatings are currently used in combination with surface sterilisation. It is, however, expensive and difficult to apply conventional coatings to existing corroded structures under water to prevent further corrosion.
In some cases, a calcareous film, a deposit of Calcium Carbonate (CaCO3) and Magnesium Hydroxide (Mg(OH)2) produced on steel structures has been proved to be an effective and an inexpensive substitute for a conventional corrosion control coating.
When deposition conditions are appropriately controlled, it provides corrosion protection for steel in seawater.
BAC Corrosion Control Ltd (BAC) and partners Mott MacDonald and The
University of Manchester have developed a patented treatment, LATreat™, to counter the problem of ALWC by applying a calcareous deposit in a controlled process. The process can be used to treat local areas where ALWC is occurring.
LATreat™ is an electrochemical process which works in a similar way to CP simply using the seawater and electricity to generate all the necessary active agents.
The treatment comprises three optimised stages, Cleaning, Sterilisation and Coating which are typically carried out sequentially using BAC equipment located within ease access of the structure to be treated.
Following lengthy studies, the endurance of the calcareous film has been evaluated the treatment is now commercially available. A Patent covering the UK has also been granted for the process.