Failed turbine blades from a marine diesel turbine engine were characterized to identify corrosion mechanisms. The blade materials were a Mar-M247 substrate with a CoNiCrAl coating. The blades were subject to a variety of damage mechanisms including oxidation/hot corrosion assisted cracking, internal corrosion by FeCMAS deposits in cooling channels, and hot corrosion pitting of the coating that reached and consumed the substrate. Scanning Electron Microscopy (SEM) and Energy-Dispersive Spectroscopy (EDS) were used to characterize the morphology and composition of the failed material. Inductively-Coupled Plasma Optical Emission Spectroscopy (ICP-OES) was used to confirm the composition of deposits. The different corrosion modes are summarized and insights into their mechanisms are discussed.