MHB and IMDG Corrosivity Classification for Cargoes
Carbon steels are conventional materials for bulk cargo shipping. Solid cargoes need to be evaluated for their corrosivity towards carbon steel to comply with the requirements of the IMSBC Code for Shipping of Bulk Cargoes in Australia.
The Curtin Corrosion Centre was assigned to assess the corrosivity of copper concentrate sample towards carbon steel, according to the International Marine Organisation (IMO) corrosivity test for bulk cargo shipping Materials hazardous only in bulk, corrosive solids (MHB(CR)), Interim guidance for conducting the refined MHB(CR) corrosivity test (MSC.1/Circ.1600).
The experimental approach used by the C.1 test method allows for reproducible corrosion testing and represents conditions in the bulk cargo shipping industry. Figure 1 illustrates the corrosion setup use to comply with the C.1 test requirements.
Figure 1: A schematic diagram of the C.1 test.
After a 2-week exposure period, the post-exposure analysis of the steel coupons involved determining uniform corrosion rates and analysing the surface intrusions as an assessment of the corrosiveness of the bulk cargo copper concentrate. Figure 2 illustrates the corrosion morphology after exposure to copper concentrate and Table 1 summarises the corrosion attack.
Figure 2; corrosion morphology after exposure to copper concentrate.
|Deepest surface intrusion analysis||Width = 4.8 mm; Depth = 254.5 μm|
|Depth-to-width ratio (dimensionless)||0.05|
|Mass loss (%)||1.21|
|Uniform corrosion rate (mm/y)||0.95|
The Curtin Corrosion Centre assisted a mining company by performing a detailed corrosivity analysis of their bulk cargo and providing the classification relating to the substance of class 8 dangerous good. As a result, the mining company could have a classification report before the ship arrival. The client could provide an appropriate declaration of their shipment on time.