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Sustainable Solution Prevents Corrosion of Quay Walls

Steel News - Published on Fri, 16 Oct 2020

Image Source: Corrosion Quay Walls
Without protection, a submerged steel surface will gradually corrode. That is why steel quay walls are generally fitted with sacrificial anodes, which draw rust away from the steel itself. There is an alternative protection method, however: using anodes that are charged with ‘impressed current’. At the HES Hartel Tank Terminal in the port of Rotterdam, no fewer than 2 km of steel quay wall are currently being protected via this method, which is more sustainable and ‘smarter’ than conventional anodes. To this day, hulls and quays are protected by fitting them with these galvanic or ‘sacrificial’ anodes. Nevertheless, the method does have its drawbacks. ‘The anodes need to be replaced once every 25 years or so. It means divers have to work weeks on end to replace all the spent anodes. This is an expensive operation and has a major impact on shipping near the quay.

The good news is that there’s an alternative method that doesn’t have this disadvantage. In this approach, the anodes are connected to a power source that puts them under a constant low voltage charge called impressed current and does not dissolve them. Metal corrodes at the molecular level: the iron reacts with the oxygen in the water and releases ions. The molecular structure of the iron changes due this natural process: its surface ‘rusts’. You can block this process by feeding the metal with ions via a current that flows through the anode. This makes the metal inert, it is no longer activated by oxygen, which in turn halts corrosion. Impressed current has been around for a few decades, but up till now it hadn’t seen too many large-scale applications in the port of Rotterdam. How this works out in practice can be seen along the quay of the HES Hartel Tank Terminal at Maasvlakte.

The quay wall of the terminal has a total length of 2 km: 1 km of deep sae quay and 1 km of quay for inland vessels . The quay has been fitted with 370 anodes. The shortest anodes along the inland shipping quay measure 5 m; the longest anodes, in the deepest section of the deep sea quay, are up to 18 m long. The anodes are charged from 52 wells with rectifier units.

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Posted By : Yogender Pancholi on Fri, 16 Oct 2020
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