Which form of corrosion occurs at high temperatures forming oxide scales on metals?

• A. Galvanic
• B. High-temperature oxidation
• C. Fretting
• D. Erosion

Answer: (B)

High-temperature oxidation is the corrosion process where metals react with oxygen when exposed to elevated temperatures to form oxide scales on the surface. This oxide layer grows as oxygen diffuses into the metal and metal ions diffuse outward; it can be protective and slow further oxidation if the scale remains adherent, but it can crack or spall and then oxidation continues more quickly. This mechanism is distinct from galvanic corrosion, which involves electrochemical potential differences between dissimilar metals in an electrolyte; fretting corrosion, which arises from wear due to micromotions at contacts; and erosion, which is physical material removal by flowing fluids or particulates.