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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. Last class - More corrosion - micro cells Welding HAZ Sensitization Ol' Harold's story. Today -

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The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

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


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Last class - happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

More corrosion - micro cells

Welding HAZ

Sensitization

Ol' Harold's story

Today -

Suppressing corrosion

Corrosion examples


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Components of a cell:

anode

cathode

electrolyte

connection


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Occlude electrolyte - coatings

asphalt

greases, oils

paints

polymers

ceramic coatings

"noble" metals


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Occlude electrolyte - coatings

"noble" metals:

unless scratch

heals, a galvanic

cell is set up


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Cathodic protection

galvanizing:

Zn coating applied by

hot-dipping

electroplating


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Cathodic protection

galvanizing:

presence of

scratch does not

promote corrosion

of protected metal

but steel helps Zn corrode


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Cathodic protection

set up cell by adding

metal which is

more anodic than

metal or alloy to

be protected


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Cathodic protection

example:

protecting ship plate


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Cathodic protection

example:

protecting hot water heater tanks


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Cathodic protection

Problem:

steel fermentation tank in brewery

sacrificial anodes add metallic ions to electrolyte


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

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


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

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


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

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"


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

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


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Anodizing

Al & other materials can be anodized

very thick oxide coating formed (8-50 microns)


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

2300x

540x

Thinking again of noble metal coatings, what about Cr plating?

Cr plating usually filled w/ microcracks due to stresses in plating


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Suppressing corrosion happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Cr plating frequently a series of layers


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Corrosion examples in shuttle mat'ls happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

60x

1x

235x

1180x


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Corrosion examples in shuttle mat'ls happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Corrosion examples in shuttle mat'ls happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Corrosion examples in shuttle mat'ls happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Corrosion examples in shuttle mat'ls happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Corrosion area effect happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Area effect:

large cathode & small anode -

corrosion accelerated

electrochemical cell current density high

try to keep potential anodic areas large relative to cathode


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Polymers - the nightmare begins happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

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


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

What are polymers? happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Why important ?

  • Long chain molecules

  • Extraordinary range of

  • physical properties

  • Many (not all) are cheap

  • Low densities


The purpose of scientific thought is to predict what will happen in given experimental circumstances all the philosoph

Assignment: happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

Review today's classnotes

a. coatings

b. cathodic protection

c. passivation

d. anodizing

e. Cr plating

f. corrosion examples

g. area effect

h. what is a polymer?

Read: pp 569-585, 589-591, chapter 14