High Temperature Corrosion: Worksheet 1

High Temperature Corrosion: Worksheet 1

1.What are the relative benefits and drawbacks of Fe3O4, Al2O3 and Cr2O3 scales in high temperature oxidation?

2.Why do alloys often show parabolic kinetics of oxidation? Derive the parabolic law for oxidation of nickel.

3.How can the resistance of a scale to spalling be improved?

4.What is a p-type oxide? What type of alloying addition would i) increase and ii) decrease the oxidation rate of nickel?

5.Describe experimental methods for determining the kinetics of scale growth for a high temperature alloy.

6.Show how the equilibrium partial pressure of oxygen in a cavity located at the metal/oxide interface on an oxidized nickel specimen can be calculated.

7.What is the mechanism of ionic transport through an Nb2O5 scale on niobium?

8.Explain why the defect concentration in NiO depends upon the partial pressure of oxygen.

9.Sketch the kinetics of oxidation of chromium in oxygen at 800oC and at 1000oC. Why are they different?