Rapid corrosion (ALWC) of harbor installations at low water
Anodes may be used to counter microbially influenced corrosion (MIC) associated with zero tidal level (accelerated low-water corrosion, ALWC).
Corrosion of steel constructions in harbors is a difficult problem. It can create dangers to traffic and affect all safety issues. Local, accelerated corrosion is a difficult problem to allow for in plans of maintenance and running of harbor installations.
Corrosion in excess of „standard corrosion level“ (0.10 to 0.15 mm per year), may be caused if a protective layer is removed by electric currents or by chemical pollutants.
Microbes can increase corrosion rates, especially near tidal zero level.
Unpredictable pollution events may occur in or near harbors. Commonly, these are associated with a boat sinking, a ship running aground, or a ship releasing bilge water into a harbour. Marine biota may suffer, and ships and harbor constructions may need cleaning. IDS owns gear for pollution prevention, such as flotgirðingar used to isolate the polluted area, and an oil skimmer which is used to remove surface oil. This is achieved with brushes which absorb the oil which then can be pumped ashore. IDS can take this gear to any port at short notice.
The Icelandic Diving Service now offers to inspect sheet piles all over the country. The inspection includes precise thickness measurements and a video recording of the inspection. A report on the condition of the þil is submitted. A 200 m long þil can be inspected in a day.
A diver carries out the inspection. All holes in the steel are measured and recorded. The diver carries a camera, and the client can watch the proceedings in real time. The video record accompanies the report.
Thickness of the steel is measured by a Tritex Multigauge Ultrasonic 5600 meter which has proved very successful in this type of work.
The measurements are made on vertical lines, spaced 5 meters apart. Up to 5 points are measured on each line. If a visual inspection suggests a need for denser measurements, the interval may be reduced to 1 meter.
Junk in harbors can damage ships and boats. IDS can map unwanted objects on the bottom, using side-scan sonar or multibeam survey. Both methods are independent of visibility and can therefore be used at any time. Most junk is to be found near piers, and objects like tires, ropes, wooden beams, steel beams and steel cables can damage propellers and steering gear. Once the distribution of junk has been mapped, divers may be deployed to clear the harbor.