Chemistry of hot corrosion

During the initiation stage of hot corrosion, elements in the alloy are oxidized and transferred from metallic atoms to the reducible substances in the deposit. To develop resistance to hot corrosion one should strive to have the superaUoys which can remain in the initiation stage as long as possible. 

In some cases of hot corrosion an increasing amount of sulphide particles becomes evident in the alloy beneath the protective reaction product barrier. In other cases, small holes become evident in the protective reaction product barrier where the molten deposit begins to penetrate it. Eventually the protective barrier formed via selective oxidation is rendered ineffective and the hot corrosion process enters the propagation stage (Pettit and Giggins, 1987). 

2 Schematic diagram showing a Na2S04 deposit upon an alloy separating the alloy from the gas phase (Pettit and Meier, 1984). 

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