2 Corrosion mechanism and causations
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Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC.1/Circular.1421 – Guidelines on Exemptions for Crude Oil Tankers Solely Engaged in the Carriage of Cargoes and Cargo Handling Operations not Causing Corrosion – (13 June 2012) - Annex – Guidelines on Exemptions for Crude Oil Tankers Solely Engaged in the Carriage of Cargoes and Cargo Handling Operations not Causing Corrosion - 2 Corrosion mechanism and causations

2 Corrosion mechanism and causations

  2.1 In general, corrosion protection, either by coating or other means, is required at the top side (underdeck) part and bottom part of cargo oil tanks of crude oil tankers. However, the corrosion mechanisms are different.

  2.2 Due attention should be paid to the fact that, regardless of the nature of the cargo, the bottom side is susceptible to pitting corrosion while the upper deck side is exposed to corrosive chemical composition of inert gas, i.e. hydrogen sulphide (H2S).

  2.3 Other factors, such as oil and temperature inside the tank, are key factors in deciding on the vulnerability of these areas.

Parent topic: Annex – Guidelines on Exemptions for Crude Oil Tankers Solely Engaged in the Carriage of Cargoes and Cargo Handling Operations not Causing Corrosion
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