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.

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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
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Cathodic protection
example protecting ship plate
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Cathodic protection
example protecting hot water heater tanks
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Cathodic protection
Problem steel fermentation tank in brewery
sacrificial anodes add metallic ions to
electrolyte
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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
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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
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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"
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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
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Anodizing
Al other materials can be anodized very thick
oxide coating formed (8-50 microns)
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Thinking again of noble metal coatings, what
about Cr plating?
Cr plating usually filled w/ microcracks due to
stresses in plating
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Cr plating frequently a series of layers
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Area effect large cathode small anode -
corrosion accelerated
electrochemical cell current density high
try to keep potential anodic areas large relative
to cathode
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What are polymers? Why important ?

• Long chain molecules
• Extraordinary range of
• physical properties
• Many (not all) are cheap

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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 569-585, 589-591, chapter
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