This document discusses different theories and types of corrosion. It begins by introducing corrosion as the formation of compounds on a metal's surface through chemical reaction with its environment. It then summarizes three main theories of corrosion: (1) the acid theory involving reaction with carbon dioxide, moisture and oxygen; (2) the chemical theory involving direct reaction with gases like oxygen; and (3) the electrochemical theory involving the formation of anodes and cathodes when a metal is in contact with a conducting liquid. The document goes on to describe eight common types of corrosion in more detail.
A presentation covering the various methods of prevention of corrosion. Material selection, design of structures, alteration of materials, alteration of environment, cathodic & anodic protection, and coatings are the different methods used. These are briefly described.
14 Types of Corrosion explained in an awesome manner
Update 26 June 2019: I have enabled the Download option and now everyone can download the "Types of corrosions" PPT and reuse the slides :) I wish I have done this earlier.
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Factors affecting corrosion on the basis of nature of the metal and Nature of Corroding medium, Protection from corrosion in reference to Sacrificial protection, Cathodic protection, Metallic coatings, Organic coatings, Proper designing.
Corrosion, types of corrosion, examples and mechanism of Dry or Chemical Corrosion, Oxidation Corrosion, Nature of Oxide layer formed, Pilling - Bedworth rule, Passivity or Passivation
A presentation covering the various methods of prevention of corrosion. Material selection, design of structures, alteration of materials, alteration of environment, cathodic & anodic protection, and coatings are the different methods used. These are briefly described.
14 Types of Corrosion explained in an awesome manner
Update 26 June 2019: I have enabled the Download option and now everyone can download the "Types of corrosions" PPT and reuse the slides :) I wish I have done this earlier.
Follow my blogs at https://www.geekdashboard.com/
Factors affecting corrosion on the basis of nature of the metal and Nature of Corroding medium, Protection from corrosion in reference to Sacrificial protection, Cathodic protection, Metallic coatings, Organic coatings, Proper designing.
Corrosion, types of corrosion, examples and mechanism of Dry or Chemical Corrosion, Oxidation Corrosion, Nature of Oxide layer formed, Pilling - Bedworth rule, Passivity or Passivation
Wet or Electrochemical corrosion, Mechanism of electrochemical corrosion, Evolution of hydrogen and absorption of oxygen type cathodic reaction, Distinction between dry and wet corrosion.
Corrosion of material - Engineering MetallurgyMechXplain
The PPT is on Corrosion and Degradation of Material specifically Metal and Reason Behind it. As well as the preventive measures to be taken to prevent it.
As an old adage says, corrosion prevention must start at the blackboard, at the design stage. A good design at the blackboard is no more costly than a bad design, a bad design is always more expensive than a good design in reality. Technical design inclu- des the aspects of design that directly bear on the proper technical functioning of the product attributes that describe how it works and how it is made. Design configuration has a critical role to play in the service life of components
Wet or Electrochemical corrosion, Mechanism of electrochemical corrosion, Evolution of hydrogen and absorption of oxygen type cathodic reaction, Distinction between dry and wet corrosion.
Corrosion of material - Engineering MetallurgyMechXplain
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As an old adage says, corrosion prevention must start at the blackboard, at the design stage. A good design at the blackboard is no more costly than a bad design, a bad design is always more expensive than a good design in reality. Technical design inclu- des the aspects of design that directly bear on the proper technical functioning of the product attributes that describe how it works and how it is made. Design configuration has a critical role to play in the service life of components
Information for Primary School students on stars and constellations. This PowerPoint uses some slides from http://www.slideshare.net/winga1sm/star-powerpoint-3308182 and the rest has been created by me.
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this slide comprises of definition.rate, and types of corrosion which are found in materials in our daily life.
its contents are:
what is corrosion
what are its basic types and
what is the rate of corrosion in materials
This topic describes two main categories of corrosion. It also explains the electrochemical corrosion phenomena and the differences between the types of corrosion. This topic also states the corrosion preventive steps.
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Barrier Protection: This involves applying coatings or barriers to physically isolate the material from its environment. Common barrier materials include paints, polymer coatings, and enamels. These coatings create a protective layer that prevents corrosive agents from reaching the underlying material.
Cathodic Protection: This method involves making the metal to be protected the cathode of an electrochemical cell, thus reducing its corrosion rate. Cathodic protection can be achieved through sacrificial anodes, where a more reactive metal (such as zinc or magnesium) is connected to the metal to be protected, sacrificing itself to protect the base metal.
Anodic Protection: Conversely, anodic protection works by polarizing the metal to be protected to make it the anode in an electrochemical cell. This method is suitable for metals that exhibit passivity, such as stainless steel. By maintaining the metal in its passive state, its corrosion rate is significantly reduced.
Inhibitors: Corrosion inhibitors are chemicals that are added to the environment surrounding the metal to reduce its corrosion rate. Inhibitors work by adsorbing onto the metal surface, forming a protective layer that blocks corrosive agents from reaching the metal. Common inhibitors include organic compounds, chromates, and phosphates.
Alloying: Alloying involves mixing the base metal with other elements to improve its corrosion resistance. For example, stainless steel contains chromium, which forms a passive oxide layer on the surface, protecting the underlying metal from corrosion.
Design Modification: Sometimes, corrosion can be mitigated through design modifications that minimize exposure to corrosive environments or improve drainage to prevent the accumulation of moisture.
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Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
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The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
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Length: 30 minutes
Session Overview
-------------------------------------------
During this webinar, we will cover the following topics while demonstrating the integrations of JMeter, InfluxDB and Grafana:
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https://www.rttsweb.com/jmeter-integration-webinar
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The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
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Sectoral targets and attacks as well as the cost of ransom
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3. INTRODUCTION
Corrosion is a process of formation of
the compound of pure metal by the
chemical reaction between metallic
surface and its environment.
It is an oxidation process. It causes loss of
metal.
Hence, disintegration of a metal by its
surrounding chemicals through a chemical
reaction on the surface of the metal is
called corrosion.
3
4. Example: Formation of rust on the surface
of iron, formation of green film on the
surface of copper.
The responsible factors for the corrosion
of a metal are the metal itself, the
environmental chemicals, temperature
and the design.
4
6. (1) ACIDTHEORY
This theory suggests that corrosion of a
metal (iron) is due to the presence of
acids surrounding it.
According to this theory, iron is corroded
by atmospheric carbon di-oxide, moisture
and oxygen. The corrosion products are
the mixture of Fe(HCO3)2, Fe(OH)CO3
and Fe(OH)3.
6
8. (2) CHEMICALTHEORY OF
CORROSION
According to this theory, corrosion on the
surface of a metal is due to direct reaction
of atmospheric gases like oxygen, halogens,
oxides of sulphur, oxides of nitrogen,
hydrogen sulphide and fumes of chemicals
with metal.
The extent of corrosion of a particular metal
depends on the chemical affinity of the metal
towards reactive gas.
Oxygen is mainly responsible for the
corrosion of most metallic substances when
compared to other gases and chemicals.
8
9. There are main three types of
chemical corrosion.
(i) Oxidation corrosion (Reaction with oxygen)
(ii) Corrosion by other gases
(iii) Liquid metal corrosion
9
10. (i) Oxidation corrosion
(Reaction with oxygen)
Some of the metals directly react with
oxygen in the absence of moisture.
Alkali and alkaline earth metals react with
oxygen at room temperature and form
corresponding oxides, while some metals
react with oxygen at higher temperature.
Metals like Ag, Au and Pt are not oxidized as
they are noble metals.
10
11. • During oxidation of a metal, metal oxide is
formed as a thin film on the metallic surface
which protects the metal from further
corrosion.
• If diffusion of either oxygen or metal is across
this layer, further corrosion is possible. Thus,
the layer of metal oxide
plays an important role in the process of
corrosion.. 11
12. Oxides of Pb, Al and Sn are stable and hence
inhibit further corrosion. They form a stable,
tightly adhering oxide film.
In case of porous oxide film, atmospheric
gases pass through the pores and react with
the metal and the process of corrosion
continues to occur till the entire metal is
converted into oxide.
Porous oxide layer is formed by al- kali and
alkaline earth metals. Molybdenum forms a
volatile oxide film of MoO3 which
accelerates corrosion.
Au, Ag, Pt form unstable oxide layer which
decomposes soon after the formation,
thereby preventing further corrosion.
12
13. (ii) Corrosion by other gases
(Cl2, SO2, H2S, Nox)
In dry atmosphere, these gases react with
metal and form corrosion products which
may be protective or non-protective.
Dry Cl2 reacts with Ag and forms AgCl
which is a protective layer, while SnCl4 is
volatile.
In petroleum industries at high
temperatures, H2S attacks steel forming FeS
scale which is porous and interferes with
normal operations.
13
14. (iii) Liquid - metal corrosion
In several industries, molten metal passes
through metallic pipes and causes
corrosion due to dissolution or due to
internal penetration.
For example, liquid metal mercury
dissolves most metals by forming
amalgams, thereby corroding them.
14
15. (3) Wet or electrochemical
theory of corrosion
It is a common type of corrosion of metal
in aqueous corrosive environment. This
type of corrosion occurs when the metal
comes in contact with a conducting liquid
or when two dissimilar metals are
immersed or dipped partly in a solution.
According to this theory, there is the
formation of a galvanic cell on the surface
of metals. Some parts of the metal surface
act as anode and rest act as cathode.
15
16. The chemical in the environment and
humidity acts as an electrolyte.
Oxidation of anodic part takes place and
it results in corrosion at anode, while
reduction takes place at cathode.
The corrosion product is formed on the
surface of the metal between anode and
cathode.
16
17. Differences between dry and
wet corrosion
Dry corrosion
• Corrosion occurs in the
absence of moisture.
• It involves direct attack of
chemicals on
the metal surface.
• The process is slow.
• Corrosion products are
produced at the
site of corrosion.
• The process of corrosion
is uniform.
Wet corrosion
• Corrosion occurs in
presence of conducting
medium.
• It involves formation of
electrochemical
cells.
• It is a rapid process.
• Corrosion occurs at
anode but rust is deposited
at cathode.
• It depends on the size of
the anodic part
of metal. 17
18. Factors Influencing Corrosion
The nature and extent of corrosion depend
on the metal and the environment. The
important factors which may influence the
corrosion process are
(i) Nature of the metal
(ii) Environment
(iii)Concentration of electrolyte
(iv) Temperature
(v) Electrode potential and
(vi) Hydrogen over voltage
18
19. TYEPS OF CORROSION
There are basically eight types of corrosion
I. Uniform corrosion
II. Pitting corrosion
III. Transgranular and Intergranular
(Intercrystalline ) corrosion
IV. Exfoliation corrosion
V. Stress corrosion
VI. Crevice corrosion
VII. Galvanic corrosion
VIII. Erosion
19
20. I. Uniform corrosion
This type of corrosion develops as pits of
very small diameter, in the order of a
micrometer, and results in a uniform and
continuous decrease in thickness over the
entire surface area of the metal.
The rate of uniform corrosion can be easily
determined by measuring the mass loss, or
the quantity of released hydrogen
20
21. II. Pitting corrosion
This localized form of corrosion is
characterized by the formation of irregularly
shaped cavities on the surface of the metal.
Their diameter and depth depend on several
parameters related to the metal, the medium
and service conditions.
Unlike uniform corrosion, the intensity and
rate of pitting corrosion can be assessed
neither by determining the mass loss nor by
measuring released hydrogen. 21
22. Pitting corrosion can be assessed using three
criteria : the density, i.e. the number of pits
per unit area, the rate of deepening and the
probability of pitting.
In fact, these measurements do not make
sense because a very deep and isolated pit
results only in a small mass loss, where as a
very large number of superficial pits can lead
to a larger mass loss.
22
23. III.Transgranular and
Intergranular (Intercrystalline )
corrosion
Within the metal, at the level of the grain,
corrosion may propagate in two different
ways :
(i) It spreads in all directions, corrosion
indifferently affects all the metallurgical
constituents; there is no selective corrosion.
This is called transgranular or
transcrystalline corrosion because it
propagates within the grains. 23
24. (ii) It follows preferential paths: corrosion
propagates at grain boundaries. Unlike
transgranular corrosion, these forms of
intercrystalline corrosion consumes only a
very small amount of metal, which is why
mass loss is not a significant parameter for
assessment of this type of corrosion.
It is not detectable which naked eye but
requires microscopic observation, typically at
a magnification of 50. When penetrating into
the bulk of the metal, intercrystalline
corrosion may lead to a reduction of
mechanical properties and even lead to the
rupture of components. 24
25. IV. Exfoliation Corrosion
Exfoliation corrosion is a type of selective
corrosion that propagates along a large
number of planes running parallel to the
direction of rolling or extrusion.
Between these planes are very thin sheets of
sound metal that are not attacked, but
gradually pushed away by the swelling of
corrosion products, peeling off like pages in a
book; hence the term exfoliation corrosion.
The metal will swell, which results in the
spectacular aspect of this form of corrosion. 25
26. V. Stress corrosion
This type of corrosion results from the
combine action of a mechanical stress
(bending, tension) and a corrosive
environment.
Each of these parameters alone would not
have such a significant effect on the
resistance of the metal or would have no
effect at all.
26
27. VI. Crevice corrosion
Crevice corrosion is a localized corrosion in
recesses :
overlapping zones for riveting, bolting or
welding, zones under joints and under
various deposits. These zones also called
crevices, are very tiny and difficult to access
for the aqueous liquid that is covering the
rest of the readily accessible surfaces.
This type of corrosion is also known as
deposit attack.
27
28. VII. Galvanic corrosion
When two dissimilar metals are in direct
contact in a conducting liquid, experience
shows that one of the two may corrode. This
is called galvanic corrosion. The other metal
will not corrode; it may even be protected in
this way.
This corrosion is different in its kind and
intensity from the one that would occur if
they were placed separately in the same
liquid. 28
29. Unlike other types of structural corrosion,
galvanic corrosion does not depend on the
metal’s texture, temper, etc.
Galvanic corrosion may occur with any
metal, as soon as two are in contact in a
conductive liquid. It works like a battery.
The appearance of galvanic corrosion is very
characteristic. It is not dispersed like pitting
corrosion, but highly localized in contact
zone with the other metal.
The zone affected by galvanic corrosion
often has a shinier aspect than the rest of
the surface.
29
30. VIII. Erosion
Corrosion by erosion occurs in moving
media. This type of corrosion is related to
the flow speed of the fluid.
It leads to local thinning of the metal, which
results in scratches, gullies, and undulations,
which are always oriented in the same
direction, namely the flow direction.
30
31. SpecialThanks to:
Dr. N. K. Shah (HOD)
Department of chemistry,
Gujarat University, Ahmedabad
Suresh Kumar
Research Scholar,
Department of Chemistry,
Gujarat University, Ahmedabad
31