is best placed to handle the aggressive corrosion conditions found in


marine scrubber units A corrosion specialist with Outokumpu, Björn Helmersson explains why stainless steels are the ideal choice for the aggressive corrosion conditions found in marine scrubber units.


In 2020, the International Maritime Organisation (IMO) introduced new standards intended to reduce sulphur emissions that cause acid rain and air pollution. Their main impact is that the sulphur content in the fuel oil used by merchant vessels is limited to 0.5% globally and 0.1 % in designated Emission Control Areas (ECAs) – the Baltic Sea area, the North Sea area, the United


States, Canada, and the United States Caribbean Sea area. Currently, vessel operators have two main options. They can switch to very low sulphur fuel oil (VLSFO) that contains less than the 0.5 % sulphur limit, but which is more expensive. Or they can install a scrubber that washes the vessel’s exhaust gases so that it can continue to run on high- sulphur fuel (HFO).


100 | The Report • December 2020 • Issue 94 SCRUBBER DESIGNS


Generally, the shipping industry uses wet scrubbers (see Figure 1). These exhaust gas cleaning (EGC) systems wash the exhaust gas stream by forcing it into contact with water to remove the sulphur dioxide (SO2


), a toxic


gas that is directly harmful to human health.


By Björn Helmersson


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