Chapter 13: Chemical Degradation

3/13 (No Quiz)

Material Type

1. Ceramic

2. Metal

3. Polymer

4. Composite (all 3)

Types of Degradation → depends on material + environment

1. Chemical

2. Mechanical

3. Electrical

Materials degrade (different types) → degradation effects ↔ organism/bio response

Chemical Degradation: oxidation + reduction

• usually oxidation of metals

• Oxidation is LOSS of electrons

• Reduction is GAIN of electrons

You should know top reactive elements on reactivity series*

Approaches of Chem Degradation:

1. Reactivity Series

2. Pourbaix Diagram

3. Corrosion + Electrochemistry Studies

Interesting Values: slide 9 **

• FOR BIO STUFF USE STAINLESS STEEL (mostly iron, some carbon + other stuff)

  • Fe2+ + 2e- → Fe -0.44 V

  • We expect if we put any of this stuff into the human body, it will corrode

• regular bridge use regular steel

• Cobalt Chromium Alloys (be careful about circulation in human body bc anemia)

• Titanium Alloys (most bio compatible)

Pourbaix Diagram: slide 11**

• what is this

• how do I read it

• why is it important

Types of Corrosion

Guessing Corrosion (pt1):

1. a

2. a

3. a

4. a

5. a

6. a

Guessing Corrosion (pt2):

1. a

2. a

3. a

4. a

5. a

What types of corrosion should you worry about in these start from 11 clockwise:

Mechanical/chem stress → bio response therefore put pacemaker in good location