What Does High-Temperature Corrosion Mean?
High-temperature corrosion is a chemical attack from gases, solid or molten salts, or molten metals, typically at temperatures above 750ºF (400°C). Different types of high-temperature corrosion include:
- Flue gas and deposit corrosion
Industrially, high-temperature corrosion is a significant issue. Any component that is exposed to a high temperature in a non-inert environment is potentially at risk. It is a widespread problem in various industries such as:
- Power generation (nuclear and fossil fuel)
- Aerospace and gas turbines
- Heat treating
- Mineral and metallurgical processing
- Chemical processing
- Refining and petrochemical
- Pulp and paper
- Waste incineration
High-temperature corrosion is also known as dry corrosion or scaling.
Corrosionpedia Explains High-Temperature Corrosion
High-temperature corrosion is a mechanism of corrosion that can take place in gas turbines, diesel engines, furnaces or other machinery coming in contact with hot gas containing certain contaminants.
Fuel sometimes contains vanadium compounds or sulfates which, having a low melting point, can form compounds during combustion. These liquid melted salts are strongly corrosive for stainless steel and other alloys normally inert against corrosion and high temperatures. The same kind of attack has been observed for potassium and magnesium sulfate.
Almost all metals, alloys and materials of technological interest oxidize and corrode at high temperatures. On the basis of environment and temperature, the following variables wildly vary:
- Nature of the corrosion products
- Rate of corrosion
Oxidation is by far the most common form of high-temperature corrosion—almost all useful metals and alloys oxidize above a certain temperature, leading to:
- Loss of material
- Changes in physical properties
Furthermore, high-temperature corrosion is not restricted to the gaseous phase—solid ash and salt deposits contribute to the corrosive effect, with associated erosion and removal of scale. In the liquid phase, molten metals and molten salts pose their own unique challenges, causing highly complex and environment-dependent corrosion. Gaseous attack is not limited to oxygen however, with sulfur-bearing gases, carbon oxides and many other elements all attacking materials in different manners.
Materials for high-temperature service cannot be selected on the grounds of their corrosion resistance alone. Creep strength and structural stability must also be taken into account.