An experimental investigation of the corrosive influence of SO 2 relative to H 2 SO 4 of marine engine cylinder liners

The present study investigates the corrosive influence of SO₂ on cylinder liner wear relative to H₂SO₄. Several charge gases with different concentrations of SO_2, H₂SO₄, and H₂O in air are fed to a motored light duty test engine that operates at 98 revolutions per minute (rpm) in order to resemble the corrosive combustion gas and cycle speed of large low‐speed two‐stroke marine engines. When the trapped cylinder gas is compressed, the H₂SO₄ and H₂O vapours can condense on the oil wetted liner surface, and the SO₂ can be absorbed in the oil film. Hereby the liner surface may be exposed to a corrosive attack. A blend of a base oil and a commercial marine engine cylinder lubrication oil is used in the experiments. During testing, oil samples are extracted from the engine and subsequently analysed for iron and sulphur accumulation (using an energy dispersive X‐ray fluorescence spectrometer) in order to couple cylinder liner wear with the amount of SO₂, H₂SO₄, and H₂O in the charge gas. In contrast to H₂SO₄, the wear of SO₂ is weak (if any), although the SO₂ accumulates/reacts considerably in the lube oil. The highest wear rates are found at elevated H₂O concentrations.