【Daily Question】12.7 Thermal Corrosion (2 wealth points for a reply, +3 to +8 wealth points for a correct answer)
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Briefly describe the temperature of thermal corrosion and the medium conditions? The phenomenon in which deposits form on the surface of metal materials at high temperatures as a result of reactions with environmental factors, and corrosion accelerates under the combined action of oxygen and other corrosive gases
High-temperature thermal corrosion refers to the thermal corrosion that occurs in a temperature range of 825–950°C; especially when the temperature is above 884°C (the melting point of pure sodium sulfate), the deposited salt film is in a molten state. Its typical microstructure results from the depletion of the elements in the matrix that can participate in reactions due to the formation of sulfides. Low-temperature thermal corrosion refers to thermal corrosion that occurs at temperatures between 650 and 750°C. Although, in terms of temperature, the overall salt film has not reached its melting point, the low melting points of metal sulfides allow for the formation of metal-metal sulfide eutectics with even lower melting points, thereby accelerating high-temperature corrosion.
Above 240 degrees, in an environment of naphthenic acid, elemental sulfur, and hydrogen sulfide
Thermal corrosion is a phenomenon in which metal materials, at high temperatures, experience accelerated corrosion due to deposits that form on their surfaces as a result of reactions with environmental factors; oxygen and other corrosive gases further accelerate this corrosion process. Classification: (High-temperature thermal corrosion, which occurs at temperatures of 825–950 degrees); (Low-temperature thermal corrosion, which occurs at temperatures of 650–750 degrees). Sulfur has a significant impact, especially as it exacerbates thermal corrosion when NaCl is present in the gas.
Temperature: Thermal corrosion requires molten salts. The temperature range at which superalloys are subject to thermal corrosion is generally around 800–1000°C. However, in the presence of SO3, this substance reacts with the metal oxides on the surface of the components to form sulfates; together with Na2SO4, these substances create a low-boiling eutectic. As a result, severe thermal corrosion can occur even at temperatures below the melting point of sodium sulfate (884°C), specifically in the range of 600–750°C. Medium composition: Sulfur has a significant impact; especially when NaCl is present in the gas, it exacerbates thermal corrosion
Corrosion that occurs under high temperatures and in molten sediments, as a result of the combined action of oxygen and other corrosive gases, is known as thermal corrosion