Calculate material weight gain and parabolic/linear rate constants.
Calculate Both
Linear Only
Parabolic Only
Weight Gain per Unit Area (ΔW/A):0.00 mg/cm²
Linear Rate Constant (kₗ):0.00 mg/(cm²·h)
Parabolic Rate Constant (kₚ):0.00 mg²/(cm⁴·h)
Understanding Oxidation Rate Calculations
In materials science and metallurgy, the oxidation rate determines how quickly a metal or alloy reacts with oxygen to form an oxide scale. This process is critical for predicting the service life of components in high-temperature environments, such as jet engines, industrial furnaces, and chemical reactors.
Linear vs. Parabolic Oxidation Laws
Depending on the properties of the oxide layer being formed, oxidation typically follows one of two primary kinetic models:
Linear Rate Law: This occurs when the oxide scale is porous, cracked, or non-protective. Oxygen can easily penetrate to the metal surface, leading to a constant reaction rate. The formula is: ΔW/A = kₗt.
Parabolic Rate Law: This occurs when a dense, protective oxide layer forms. The reaction rate decreases over time because oxygen ions or metal ions must diffuse through the thickening oxide scale. The formula is: (ΔW/A)² = kₚt.
Common Rate Constants for Industrial Alloys
Refer to the table below for typical oxidation behavior observed in common engineering materials at elevated temperatures:
Material Type
Typical Scale
Kinetic Behavior
Pure Iron (Low Temp)
FeO, Fe₂O₃
Parabolic
Chromium-based Alloys
Cr₂O₃
Parabolic (Slow)
Magnesium
MgO
Linear (Porous)
Alumina-formers
Al₂O₃
Parabolic (Very Slow)
Example Calculation
If a stainless steel sample with a surface area of 5 cm² gains 20 mg of mass after being exposed to air at 800°C for 50 hours, the oxidation metrics are: