Loss of functional properties of a material due to environmental interaction.
Types
- Corrosion
Electrochemical degradation of metals. Requires an electrolyte and electron transfer. - Oxidation
Reaction with oxygen. Forms a surface oxide layer. Common in metals at high temperatures. - Swelling
Polymer absorbs a solvent and expands. Weakens the structure. - Dissolution
Gradual dissolving of the material in a solvent.
Rate-Affecting Factors
- Temperature
Higher temperature accelerates all degradation mechanisms. - Concentration of reactant
Higher concentration increases reaction rate. - Surface area exposed
Larger area means more reaction sites. - pH
Acidic or alkaline environments accelerate corrosion in metals.
Resistance of Ceramics
Ceramics have ionic or covalent bonds with no free electrons. Electrochemical corrosion requires free electrons, so it does not occur. Ceramics are also chemically stable in most solvents. That’s why glass is used to contain liquids and store reactive chemicals.