Corrosion and grooving on the blading of an exhaust driven turbocharger is caused by certain components of residual fuel oils. These components are vanadium, sodium, and __________.

Correct Answer: Option D — sulfur

High-temperature residual fuel combustion produces corrosive ash containing vanadium pentoxide and sodium sulfate. Combined with sulfur oxides, these compounds create low-melting-point eutectics that attack and destroy high-alloy turbine blading through severe high-temperature corrosion and grooving.