CORROSION

1
CORROSIONThe Best Kept Secretin the Western
World
Terry MayPresident, NACE Foundation
2
Corrosion Society
3
Corrosion Society
4
Corrosion Society
5
Cost of Corrosion in 1998 GNP
6
Money
To put in perspective the annual cost of all
the natural disasters in the USA. (Hurricanes,
tornadoes, tropical storms, floods, fires etc)
17 Billion
Corrosion Costs the US economy 276 Billion per
Year or16 times as much as all the natural
disasters combined More than 1000/year/person
7
Money
25 could be saved using existing technologies
8
Environment
9
Environment
10
Safety
11
Safety
12
Safety
13
Safety
14
Application to Various Industries

• Pipelines
• Underground Storage Tanks
• Industrial Plants
• Power Generation
• Transportation

• Marine
• Waterworks
• Petrochemical Plants
• Pulp and Paper
• Real Estate
• Private Homes

15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
20
What is Corrosion?

• Corrosion is an electrochemical reaction between
  a metal andits environment
• Corrosion is the tendency of a metal to return
  to its original state
• Corrosion involves the flow of DC current
• Corrosion is a natural process

21
What causes Corrosion?

• Dissimilar metal
• Differential Aeration
• Environment concentration differences
• Bacteria
• Stress
• Erosion
• Temperature effects

22
What does Corrosion look like?

• Uniform
• Pitting
• Stress Cracking
• Intergranular
• Crevice Attack
• Erosion-Corrosion

23
General Corrosion
24
Pitting
25
Crevice Corrosion
26
Galvanic Corrosion
27
Practical Galvanic Series

• Magnesium -1.6 Volts
• Zinc -1.1
• Aluminum -1.05
• Steel (clean or shiny) -0.5 to -0.8
• Steel (rusty) -0.2 to -0.5
• Cast Iron -0.5
• Lead -0.5
• Copper or brass -0.2
• Mill scale on steel -0.2
• Carbon or graphite 0.3

ACTIVE
PASSIVE
28
Flashlight Battery

• An engineered corrosion reaction
• Zinc/Carbon cell connected with a conductive
  electrolyte
• Life depends on current load

29
Graphite-Zinc Battery
Graphite-Zinc Battery
Protective casing
Pitch Seal
Air Space
Electrolyte paste (ammonium chloride and zinc
chloride)
Zinc
Separator
Carbon rod
Negative terminal
30
What conditions are required for corrosion to
occur?

• An anode and a cathode locations with a
  difference in electrical potential (voltage)
  between them
• A metallic connection between the two points
• Both locations exposed to the same environment

31
Four Conditions of a Corrosion Cell

• Anode - where oxidation occurs
• Cathode - where reduction occurs
• Electrolyte - where ion migration occurs
• Metallic path - where electrons migrate from the
  anode to the cathode

32
Single Corrosion Cell
Microscopic View
CATHODIC SITE
ANODIC SITE
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
Fe
H
Fe
H
H
H
Fe
Fe
OH-
H
H
Fe
OH-
H
H
Fe
OH-
H
Fe(OH)2
Fe(OH)2
H
Fe(OH)2
33
The Corrosion Cell

• Metallic corrosion is an electrochemical
  reaction which involves
• a transfer of electrons
• oxidation - loss of electrons (corrosion)
• reduction - gain of electrons (protection)
• migration of ions

34
Corrosion Cell
Metallic Path
e
e
Cathode
Anode
Cu
Fe
H
H
Fe
HOH
Electrolyte
HOH
35
Practical CaseShowing Conventional Current Flow
Corrosion Current
Electrolyte (soil)
Cathode
Anode
Structure (metallic path)
36
Electrochemical Reactions

• Anode (Oxidation)
• Fe ? Fe 2e
• Cathode (reduction)
• 2H 2e ? H2
• 3O2 6H2O 12e? 12OH
• O2 4H 4e ? 2H2O
• Electrolyte
• H2O ? H OH

37
Oxidation Reaction
ELECTROLYTE
e
-
-
e
e
-

Fe
e
-
e
-
e
-
e
-
e
-

Fe
Fe

e
-
Fe

Fe

e
-
ANODE
e
-
e
-
e
-

Fe

Fe
e
-
e
-
e
-
e
-
Fe

e
-
Fe

Anodic Process
38
Reduction Reaction
ELECTROLYTE
e
-

H
e
-
H

H
H
H
H
e
-
e
-
e
-
H

e
-
H
e

-
H
CATHODE
H

e
-
H

e
-
H

e
-
H

e
-
e
-

H
e
-
e
-
H

H

e
-
H

e
-
H

e
-
H
Cathodic Process
39
Current Flow in a Basic Galvanic Cell
40
Methods of Corrosion Control

• Coating
• Cathodic Protection
• Environment Control
• Material Selection
• Design

41
Microscopic View of a Corrosion Cell
42
Cathodic Protection on a Structure (Macroscopic
view)
43
Typical Application of Cathodic Protection

• Underground pipelines
• Underground storage tanks
• Bottoms of on grade storage tanks
• Interiors of water storage tanks
• Condenser and heat exchanger water boxes
• Reinforced concrete
• Doesnt work in the atmosphere (Automobiles)

44
Preserving the Past
45
Preserving the Past
46
Preserving the Past
47
Statue of Liberty
48
Just Flying  along, enjoying the ride....
what's so cool is they actually pay  me to do
this! 
49
Hmmm. Strange sound.   Something feels
 different. 
50
Hey, why am I looking up.??
51
Whoa here, what the hell?  Controls aren't
working
52
Time for a mirror check.  Hey, where's the  rest
of my F-15.?
53
Uh oh, it's  over there.  I think I've got a
definite "Aw, sht" going here...
54
I gotta wonder, am I the first guy to ever
 experience " cockpit-airframe separation
anxiety".
55
I'm outta here. But  first the canopy has to go.
56
Hey GREAT!   That worked as advertised.  Things
are looking up!
57
OK, now it's my turn to go.  I'm gone - soon as I
 find the eject handle.
58
Oh yeah, that's what I'm talking about.   Looks
like it's going to be just another "average day
at the office."  
59
(No Transcript)