ClassNK warns scrubber corrosion issues could lead to a serious accident

Japanese classification society ClassNK has warned in a technical note to clients of a number of incidents of sea water leaks from scrubber kits due to corrosion around certain welded parts of the exhaust gas cleaning kits.

ClassNK said it had received several reports of leaks and is concerned heavy water ingress into a ship’s engine room could cause a serious accident. The Tokyo organisation provided images of some of the corrosion issues it had detected (see below).

ClassNK is advising masters to carry out regular checks of scrubber discharge water lines.

Last September, thousands of Splash readers watched a 50-second video (see below) showing hundreds of gallons of water pouring into the engine room of an unspecified vessel, likely the result of a corrosion issue with a scrubber.

At a Maritime CEO Forum from 2018, Bjørn Højgaard, CEO of shipmanagement giant Anglo-Eastern, warned that scrubbers are sensitive pieces of equipment sitting in the hostile, hot and acidy environment of a ship’s funnel.

“There are going to be plenty more maintenance issues than people expect,” Højgaard told the exclusive shipowner gathering. He went on to recount how one car carrier owner he knows had budgeted $10,000 a year in scrubber maintenance per ship. In the first year alone that owner had to spend $100,000 in scrubber maintenance per ship.

Norwegian P&I club Gard stated in a note to clients last October that it has seen a few incidents where within 10-15 months of an open-loop scrubber being installed, corrosion of an overboard distance piece or in its immediate vicinity has resulted in water ingress into areas such as the engine room, ballast tanks and cargo holds.

Singapore’s Maritime and Port Authority (MPA) issued extensive advice on scrubber maintenance six months ago.

“It is imperative that the structural integrity of the scrubber and associated pipework is constantly checked for signs of leakage or corrosion,” MPA stated, adding: “Aside from the video, there are also reports of scrubber corrosion repairs being required less than six months after installation. In view of the acidic nature of the scrubber washwater, correct material selection for the scrubber body, pipework, components and accessories, together with good installation workmanship are critical to avoid subsequent safety issues.”

Sam Chambers

Starting out with the Informa Group in 2000 in Hong Kong, Sam Chambers became editor of Maritime Asia magazine as well as East Asia Editor for the world’s oldest newspaper, Lloyd’s List. In 2005 he pursued a freelance career and wrote for a variety of titles including taking on the role of Asia Editor at Seatrade magazine and China correspondent for Supply Chain Asia. His work has also appeared in The Economist, The New York Times, The Sunday Times and The International Herald Tribune.


  1. The ClassNK report suggests to me that the issue you raise in your report is more to do with the ‎integrity of the weld and poor inspection. Clearly, inadequately welded seams will lead to corrosion ‎problems. The problem here therefore is not that use of the technology itself leads to corrosion, but the ‎welding and installation, which one would assume should have been picked up by the classification ‎societies before they sign the system off for operational, shipboard use.
    As CSA 2020 members have ‎advised on a number of occasions, the quality of materials – which includes the weld – is imperative to ‎their safe and effective operation.”‎

  2. I’ve already seen a number of ships returning to service from post-shipyard work, which included installation of a scrubber. Some inventive installations of course, but most all were “squeezed” within existing ship’s stack structure as part of the larger accommodation or house. THIS, specifically done, to minimize the impact on diminishing volume available for revenue earning space in cargo holds. Clearly, I’m speaking about container ships and auto carriers. Haven’t seen any yet on tankers or bulkers.

    But the video highlights the flaw in such an installation and design. Where does all that salt water go when it leaks? Down. Landing on the engine spaces under it.

    All the expert welding and use of the best material in the world doesn’t mean a thing, once a ship puts to sea and hits the first impacts of bad weather and the entire system starts getting tweeked from vibration, pounding, rolling, etc. Leaks develop. Cracks occur. Eventually the engineers onboard are trying to stop leaks everywhere that are raining salt water down on top of other E/R components and machinery, exacerbating problems further.

    Now … introduce the Chinese shipyard factor of high quality materials and excellent labor. Yes, I’m being facetious here … and now one can assume this is a nightmare simply waiting to occur on a regular and routine basis on any ship. Where were the class societies on this concept?

    And all this because we wanted cleaner air? Yes. But making the ocean dirty was ok. Got it.

  3. Completely with you on that Ed Enos.

    The shoddy workmanship and “economic” installation paradigm being followed in overbooked yards in china, is very encouraging for incidents to happen.

  4. Combination of factors, most of current design team are drawing board tigers, combined with bad workmanship, labour fatigue, tight timeline, too competitive pricing…… leading to heavy rain in ER, really worrying.

  5. Is this an issue with a particular manufacturer or installer? Or across the fleet?

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