1. The purpose of scientific thought is to predict what will happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.
– Feynman

2. Suppressing corrosion
Cathodic protection
example:
protecting ship plate

3. Suppressing corrosion
Cathodic protection
example:
protecting hot water heater tanks

4. Suppressing corrosion
Cathodic protection
Problem:
steel fermentation tank in brewery
sacrificial anodes add metallic ions to electrolyte

5. Suppressing corrosion
Cathodic protection
Different approach:
Impose a voltage across cell formed by tank (cathode) and an inert anode
choice of anode material:
very inert material like Pt
but oxygen gas produced at anode

6. Suppressing corrosion
Cathodic protection
Different approach:
Impose a voltage across cell formed by tank (cathode) and an inert anode
choice of anode material:
use carbon - inert
C + O2  CO2

7. Suppressing corrosion
Cathodic protection
"…..join in a planned discussion of whether it is best to use copper tubing coils or stainless steel tubing coils inside of a stainless steel beer fermenter, the coils being used as a chiller? There has been a discussion in another brewing forum about competing concerns between the two, i.e., copper conducts heat better and is easier to bend, versus copper will slowly dissolve in the acidic environment of beer"

8. Suppressing corrosion
Use passivated materials
Ni - NiO
Ti - TiO2
Al - Al2O3
COR-TEN:
0.19% C
0.30% Cu
0.40% Ni
0.50% Cr
0.05% V

9. Suppressing corrosion
Anodizing
Al & other materials can be anodized
very thick oxide coating formed (8-50 microns)

10. Suppressing corrosion
Thinking again of noble metal coatings, what about Cr plating?
540x
2300x
Cr plating usually filled w/ microcracks due to stresses in plating

11. Suppressing corrosion
Cr plating frequently a series of layers

12. Corrosion examples in shuttle mat'ls

13. Corrosion examples in shuttle mat'ls

14. Corrosion examples in shuttle mat'ls

15. Corrosion examples in shuttle mat'ls

16. Corrosion examples in shuttle mat'ls

17. Corrosion examples in shuttle mat'ls
Area effect:
large cathode & small anode -
corrosion accelerated
electrochemical cell current density high
try to keep potential anodic areas large relative to cathode

18. Polymers - the nightmare begins
I am inclined to think that the development of polymerization is, perhaps, the biggest thing that chemistry has done, where
it has the biggest effect on
everyday life
LORD TODD
President of the Royal
Society of London

19. What are polymers? Why important ?
Long chain molecules
Extraordinary range of
physical properties
Many (not all) are cheap

21. Assignment:
Review today's classnotes
a. cathodic protection
b. passivation
c. anodizing
d. Cr plating
e. corrosion examples
f. area effect
g. what is a polymer?
Read: pp , , chapter 14