Corrosion Products in Supercharger of Marine Engine by Running Sea Water

The study of cooling condition of exhaust gas for high efficient marine diesel engine [Part 1]

Abstract

For the cooling of exhaust gas of marine engine, natural sea water or pressed fresh water are employed. Sometimes, a lot of corrosion products were formed in the supercharger and disturbed cooling effect. Cylindrical test pieces were prepared with the same quality of cast iron of the supercharger.
Flow sea water outside of the test pieces and heat them by cartridge heater as required. The flow rates were 0.1-0.7m/s and the temperatures of the test pieces were kept at 45°C-70°C is six steps. The flow rates and temperatures were recorded automatically.
The corrosion products on the test pieces were tested by X-ray diffractometer and α-Fe₂O₃, γ-Fe₂O₃, Fe(OH)₂, Fe(OH)₃, γ-FeOOH and Fe₃O₄ were analyzed by their reflect angles.
In the case at 44°C unheated, majority corrosion product was approximately γ-FeOOH (45%), and others were Fe₃O₄ (20%), γ-Fe₂O₃ (14%) and α-Fe₂O₃ (7%). On the other hand, heated at 49°C, the order was Fe₃O₄ (46%), γ-Fe₂O₃ (26%), α-Fe₂O₃ (9%) and γ-FeOOH (7%).
In the effect of flow rate at 45°C and 55°C, α-Fe₂O₃ and γ-FeOOH were decreasing and Fe₃O₄ and rate of corrosion were increasing with the flow rate at 45°C, and α-Fe₂O₃ and γ-FeOOH were decreasing and rate of corrosion was increasing with the flow rate at 55°C.
The origin of the corrosion was presumed by the composition of the corrosion products in the supercharger.