Materials for engineering, 3rd Edition - (Malestrom)

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Materials for engineering
polybutadiene), acquire their full strength during the high-temperature paintcuring
cycle.
3.4 Degradation of metals and alloys
Metallic engineering components may degrade by chemical attack from their
environment, that is by oxidation and corrosion, or by physical attrition due
to wear. We will consider these situations in turn.
3.4.1 Oxidation of metals and alloys
Oxidation is important when alloys are used at elevated temperatures: a
surface scale forms on the material and continued oxidation proceeds by the
diffusion of metal ions, possibly oxygen ions and certainly electrons through
the oxide layer. The oxidation process for the formation of a coherent film
(i.e. one free from cracks and cavities) can be represented schematically by
a primary cell as shown in Fig. 3.33.
Metal Film Gas
e
O 2
M z+ O 2–
O 2–
P
Anode
3.33 Schematic oxidation process.
Cathode