View
229
Download
0
Category
Preview:
Citation preview
7/30/2019 OGF AIM Course 3 Module 1
1/18
MODULE 1CORROSION LANGUAGE
AND TERMINOLOGY
7/30/2019 OGF AIM Course 3 Module 1
2/18
Cost of Corrosion
Fundamental Chemistry
Cells and electrochemistry
Forms of Corrosion
OVERVIEW
7/30/2019 OGF AIM Course 3 Module 1
3/18
WHAT IS CORROSION?
Spontaneous , exothermic reaction of a metal with its
environment to form compounds.
The metal reverts back to the natural form found in nature.
In order to made metals (smelting, or reduction), chemical
energy is given to the ore material to make it a metal.
Thus metals contain more energy than rust.
The rusting process releases this energy back to the
environment.
7/30/2019 OGF AIM Course 3 Module 1
4/18
COST OF CORROSION
Annually, between 3~ 6% of GDP.
The US spends approx. 276 Billion annually (1999 figures).
( equal to the DOD budget!)
In the UAE the GDP in 2008 was 792 Billion Dhs. Cost of
corrosion was therefore between 24 and 48 Billion Dhs. But, of these costs, between 20 and 40% is preventable, using
current technology and best practices.
The UAE economy could therefore save between 5 and 10
Billion Dhs annually if best practices were implemented.
Current world annual cost of corrosion: $3.3 Trillion.
7/30/2019 OGF AIM Course 3 Module 1
5/18
DIRECT VERSUS INDIRECT COSTS
Direct costs:
Replacement of infrastructure.
Product loss.
Plant shutdown.
Corrosion resistant materials. Cathodic Protection.
Coatings.
Inhibitors.
Manpower.
Inspection. Loss of life/ injury.
Loss of reliability (redundancy).
Indirect costs:
Loss of consumerconfidence.
Disruption to society.
Litigation. Fines.
Increased regulation.
Failure analysis.
Research anddevelopment.
Education and training.
7/30/2019 OGF AIM Course 3 Module 1
6/18
FORMS OF CORROSION
Uniform
Galvanic
Dealloying
Pitting
Crevice
Stress Corrosion
Cracking Intergranular
Corrosion
Erosion Corrosion
Fretting
Microbiological
CorrosionHigh Temperature
Corrosion
Hydrogen Damage
Sulfide StressCorrosion
7/30/2019 OGF AIM Course 3 Module 1
7/18
7/30/2019 OGF AIM Course 3 Module 1
8/18
7/30/2019 OGF AIM Course 3 Module 1
9/18
CORROSION
FUNDAMENTALSChemistry
7/30/2019 OGF AIM Course 3 Module 1
10/18
ATOMS AND IONS
Elements are unique types of atoms.
Nucleus containing:
Protons
Neutrons
Orbiting electrons
Listed in the Periodic Table of elements
Chemistry involves adding and subtracting electrons to atoms.
Since electrons are charged, the resulting IONS have
electrical charge.
7/30/2019 OGF AIM Course 3 Module 1
11/18
THE PERIODIC TABLE OF THE ELEMENTS
7/30/2019 OGF AIM Course 3 Module 1
12/18
IONS
However, electrons are negatively charged, so removing
electrons makes the ion positively charged
Compounds are a positive ion and a negative ion held
together by electrostatic attraction. Overall the compound is
neutral. Fe3+ + 3Cl- FeCl3
In water, some ions are soluble and are surrounded by a
solvation sphere of water molecules. State symbol: ( aq)
7/30/2019 OGF AIM Course 3 Module 1
13/18
CHEMICAL REACTIONS AND SPONTANEITY
A chemical reaction may be spontaneous or non spontaneous.
Spontaneous reactions are exothermic.
Reverse the direction of reaction and change the energy
changes:
Spontaneous, exothermic
Fe (s) Fe2+(aq) + 2 e-
Non spontaneous, endothermic
7/30/2019 OGF AIM Course 3 Module 1
14/18
CORROSION
FUNDAMENTALS
2
Electroche
mistry
7/30/2019 OGF AIM Course 3 Module 1
15/18
ELECTROCHEMISTRY
Corrosion is electrochemical.
The transfer of electrons from one substance to another.
Spontaneous chemical react ions liberate energy. This energy
can be used to push electrons around a circuit, giving them a
voltage.
The materials proper ties change:
Fe (s) Fe2+ (aq) + 2 e-
In order for corrosion we need 4 things:
Anode
Cathode
Electrical path
electrolyte
7/30/2019 OGF AIM Course 3 Module 1
16/18
ELECTRODES NEEDED FOR CORROSION
ANODE CATHODE
Oxidation (loss of
electrons).
Corrosion.
Source of electrons.
More Active metals.
Low [O2].
Reduction (gain of
electrons).
Protection from
corrosion.
Consumption of
electrons.
More Noble metal.
High [O2].
7/30/2019 OGF AIM Course 3 Module 1
17/18
CONDUCTIVE PATHS NEEDED FOR
CORROSION
Metallic path Electrolytic path
Allows the movement of
ELECTRONS.
From the anode to the
cathode.
Must be made of metal.
REAL CURRENT.
Allows the movement of
IONS.
Positive ions flow from
the anode.
Must be an electrolyte
(water or a molten
salt).
CONVENTIONAL
CURRENT.
7/30/2019 OGF AIM Course 3 Module 1
18/18
Recommended