As the 2020 sulphur regulations is nearing, the scrubbers have become the most vital choice of shipowners. Yet, many aren’t aware of scrubber corrosion issues and how to deal with it. So, here’s a comprehensive guide of it as presented by Norshipping sometime back this year.
Let’s take a look at those.
Understanding of operational conditions
Before proceeding towards the corrosion issues, let’s take a look at the favourable operational conditions – from mild to severe conditions. Given below are the critical parameters that define optimal conditions.
- Temperature : 40 – 80℃ / 250 – 350 ℃
- pH of sea water = 7.5 – 8.4,
- Alkalinity = ability to resist change in pH
- Chloride content : ≥ 20.000 ppm
- Low pH ( 2–4) during some of the operation
- Addition of Sodiumhydroxide (NaOH) or not
Why does corrosion occurs?
Moving on let’s understand why and how corrosion occurs. Corrosion may be of 2 kinds – pitting corrosion and crevice corrosion – both depends on the passive layer of stainless steel used and the oxygen content necessary to maintain that passive film.
Ideally a greater than 10-5% of the passive layer greatly reduces the corrosion layer if the oxygen content is maintained at 2-3 nanometer.
The stainless steel used is vital in a scrubber as it can cause many different types of corrosion, including stress corrosion, fatigue corrosion, intergranular corrosion, galvanic corrosion, atmospheric corrosion depending upon the nature of the source agent.
Corrosion can’t be prevented without proper selection of scrubber material. Hence, it’s important not just to check the quality of the scrubber installation but also to question the manufacturer about the material used and the process of maintaining it in pristine conditions.
Many of them would have a proper maintenance program in place, enquire about it and choose wisely.
We will discuss these corrosion effects and the scrubber material selection in the next update. Stay tuned every Wednesday.
Till then write to us at [email protected] with suggestions of things that you would like us to cover.
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