Corrosion topic has been explained in detail with no plagrism

1. UNIVERSITY OF ENGINEERING & TECHNOLOGY
LAHORE
(New CAMPUS)
Engineering Materials
Corrosion of Materials
SUBMITTED TO : Sir Sulaiman
SUBMITTED BY : Usman Shahid
ROLL NO. : 2018-CH-265
SECTION : A
DEPARTMENT OF CHEMICAL ENGINEERING

2. Table of Contents
Abstract........................................................................................................................................................3
Introduction.................................................................................................................................................3
Causes of Corrosion ..................................................................................................................................4
Conditions for Corrosion of Materials......................................................................................................4
How Corrosion Occurs ..............................................................................................................................5
Corrosion Theory........................................................................................................................................5
Acid Theory for Corrosion.........................................................................................................................5
Dry or Chemical theory of corrosion.........................................................................................................6
Wet or electrochemical theory of corrosion ............................................................................................6
Corrosion theory for metals.......................................................................................................................6
Factors Associated with Corrosion............................................................................................................6
1. Factors Associated Mainly with the Material ...................................................................................6
2. Factors Which Vary Mainly with the Environment...........................................................................7
3. Oxidizing agents................................................................................................................................7
4. The electric conductivity of the electrolyte......................................................................................7
5. Temperature .....................................................................................................................................7
6. Concentration ...................................................................................................................................7
Corrosion Monitoring.........................................................................................................................9
The Rate of Corrosion ................................................................................................................................9
Methods for calculating Rate of Corrosion...............................................................................................9
Types of Corrosion....................................................................................................................................11
1. Metallic Corrosion...........................................................................................................................11
2. Non Metallic Corrosion...................................................................................................................28
Corrosion Environment............................................................................................................................31
Prevention Of Corrosion..........................................................................................................................32
Conclusion .................................................................................................................................................34
References..................................................................................................................................................35

3. CORROSION of MATERIALS
Abstract
Corrosion is an electrochemical reaction that occurs in many forms, such as chemical
corrosion and air corrosion, which ultimately is the most common form. Corrosion has
been found to be the most important cause of failure. This report identifies types of
corrosion such as uniform corrosion, fretting corrosion, and corrosion that is common in
some areas and causes high levels of work failure. In addition, corrosion accelerates
fatigue, irritability and wear, which can cause flexibility or cracking of the material.
Corrosion can occur anywhere, depending on the nature of the material. However, as
corrosion is widespread, it is advisable to take effective precautions when it comes to
preventing corrosion. All those factors, theories of corrosion, rate prediction and
prevention is discussed.
Introduction
Corrosion is the deterioration of an object due to a chemical reaction between it and its
environment. Both the type of material and the natural environment, especially the
content-related mirrors, determine the type and degree of degradation.
Ensuring long-term free operation and problems for the media is very important to be
aware of the corrosion and the impact it can have on the product and the system in the
operating environment.
When material possessions appear, their physical properties change. Corrosion is the
most common result of electrochemical reactions between objects and objects in their
location. The most common types of corrosion appear are caused by electrochemical
reactions. Normal corrosion occurs when most or all atoms in the same metal cell are
released, damaging the entire earth. Most metals are easily oxidized: they often lose
electrons in oxygen (and other substances) in air or water. As oxygen is reduced (it gets
electrons), it forms oxide through iron.
Much of the material damage and subsequent failure of the part caused by corrosion can
be removed by selecting the good features of a given application.
The corrosion is mainly dependent on:
• Oxygen, chloride and/or sulphide content.
• Temperature.
• pH - value.

4. Corrosion can also be defined as when a refined metal is naturally converted to a more
stable form such as its oxide, hydroxide or sulphide state this leads to deterioration of the
material.
All materials can corrode. Some, like pure metal, corrodes quickly. Stainless steel,
however, which combines iron and other alloys, is slow in scale and is therefore
frequently used.
All small group of metals, called the Noble Metals, are much less reactive than others
because of nearly filled outer shell. As a result, they corrode very less. But they are, in
fact, the only metals that can be found in nature in their purest form. The Noble Metals
although they are often very valuable and costly. They include rhodium, palladium,
silver, platinum, and gold.
Corrosion seeks to reduce the force that binds the metal. The end result of corrosion
involves an oxidized iron atom, in which it loses one or more electrons and leaves the
bulk metal.
Causes of Corrosion
Material corrodes when in contact with another substance such as oxygen, hydrogen,
gases or even pollutants and bacteria. Corrosion can also occur when metals such as
metal are subjected to extreme pressure causing the material to slip and crack.
Conditions for Corrosion of Materials
There are three main components necessary for corrosion to occur:
1. Material (example: iron)
2. Oxygen (usually from the atmosphere)
3. An electrolyte (usually water)
Many of the materials used in production come naturally from ore and therefore have to
be separated from the outside, leading to reduced stability. These metals, like iron, will
simply return to their natural parts. Corrosion products often reflect the natural state of
the metal, both physically and in terms of oxidation.
The placement of steel in the Galvanic Series will have an impact on order; the higher the
steel in the Galvanic Series the less likely it is to corrode. This effect is exacerbated when
two metals in different parts of the Galvanic Series come in contact: the upper bouts
featured two cutaways, for easier access to the higher nodes, as seen on the sacrifice

5. anodes. Significant pressure points in the material area can deal with corrosion quickly.
Other environmental factors contribute to decomposition such as pH, salt concentration,
and oxygen consumption, as well as water flow and heat.
How Corrosion Occurs
Corrosion can occur in two general ways; over the entire surface of the material
(Generalized Corrosion), or in local spots or areas (Localized Corrosion).
• Generalized Corrosion: Usually, it does not, except in acidic conditions. This
similar corrosion of the metal is rare and leads to a complete reduction but has
little effect other than the conditions of fatigue and stress.
• Localized Corrosion: The most common, and most detrimental, form of localized
corrosion is pitting. Pitting is when the attack happens in one single location on
the surface and creates a pit, or small cavity, in the metal. This type of rust attack
is difficult to prevent, engineer, and it is often difficult to detect before structural
failure due to cracking. Pipes are often compromised due to this effect of pitting.
The conductive properties of metal enable the oxidation and reduction steps that occur
during corrosion to take place at separate sites on the metal’s surface. Iron ore properties
make oxidation energy and the reduction steps that occur during filling occur at different
sites in the metal area. The conduction allows electrons to flow from the anodic regions
to the cathodic regions of the metal.
Corrosion Theory
There are Three theories for corrosion
1. Acid Theory for corrosion
2. Dry or Chemical theory for corrosion
3. Galvanic or Electrochemical or Wet theory for corrosion.
Acid Theory for Corrosion
Acid theory suggests that corrosion of a metal (iron) is due to the presence of acids
around 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)3 , Fe(OH)CO3
and Fe(OH)3 .The chemical reactions suggested are given below This theory is supported
by the analysis of rust that gives the test for CO2 ion.

6. Dry or Chemical theory of corrosion
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. Oxygen is mainly responsible for the corrosion of most metals
when compared to other gases and chemicals. There are three main types of dry
corrosion. 1. Oxidation corrosion (Reaction with oxygen) 2. Corrosion by other gases
such as Cl2, SO2, H2S.
Corrosion by other gases such as Cl2, SO2, H2S, NOx In dry atmosphere, these gases
react with metal and form corrosion products which may be protective or non-protective.
Wet or electrochemical theory of corrosion
This type of corrosion occurs when the metal comes in contact with a continuous liquid
or when two incompatible metals are immersed or immersed in part of the solution.
There is a galvanic cell formation on the surface of the metals. Some parts of the metal
act as an anode and some act as a cathode. Organic and humid chemicals act as
electrolytes. Oxidation of the anodic component occurs and results in corrosion of the
anode, while reduction occurs in the cathode. The corrosion product is made over metal.
Corrosion theory for metals
The term corrosion can be applied to all materials, including non-metals. But in practice,
the word corrosion is mainly used in conjunction with metallic materials.
Why do metals corrode? With the exception of gold, platinum and a few others, metals
do not occur in nature in their pure form. They are usually chemically bound to other
substances in ores, such as sulphides, oxide, etc. Energy should be used (e.g. in an
explosive furnace) to extract metals from sulphides, oxide, etc. to obtain pure metals.
Corrosion products are produced in the rust zone. • The process of rust is generally the
uniform.
Accordingly we list below some of the more important factors
Factors Associated with Corrosion
1. Factors Associated Mainly with the Material
• Effective electrode potential of a material in a solution
• Overvoltage of hydrogen on the metal

7. • Chemical and physical homogeneity of the material surface
• Inherent ability to form an insoluble protective film
2. Factors Which Vary Mainly with the Environment
• Hydrogen-ion concentration (pH) in the solution
• Influence of oxygen in solution adjacent to the metal
• Specific nature and concentration of other ions in solution
• Rate of flow of the solution in contact with the metal
• Ability of environment to form a protective deposit on the metal
• Temperature
• Cyclic stress (corrosion fatigue)
• Contact between dissimilar metals or other materials as affecting localized
corrosion.
3. Oxidizing agents
The process of corrosion has the conditions for anodic reactions and cathodic
reactions that occur simultaneously. An anodic reaction causes the material to
corrode. The oxidizing agent must be present in the cathodic reaction, and the most
common agents are dissolved oxygen or hydrogen ions. If the availability of
oxidizing agents is restricted, the corrosion process will be prevented or completely
eliminated. Hydrogen concentration can be easily measured as pH-value. Oxygen is
usually present in water, but not in sewage due to oxygen-eating bacteria.
4. The electric conductivity of the electrolyte
Corrosion induces electrochemical reactions, and increased electrolyte electrical
activity will therefore increase the level of corrosion. In seawater the chloride
content creates an increase in activity.
5. Temperature
An increase in temperature in general will result in an increase in the rate of
corrosion. But there is a limitation is that temperatures of up to 10 ° C will double
the rate of degradation.
6. Concentration
An increased concentration will normally increase the corrosion rate up to a
maximum level. Increased strength tends to increase the level of rust to a higher
level. A higher concentration than this will not give a higher roughness ratio. e.g. a
collection of chloride above 1500 ppm will not increase the rust level.

8. In any discussion of the chemical reaction it is best to distinguish the factors that
determine the tendency or driving force of the reaction from those that influence the rate
of reaction generated by the presence of this tendency. This tendency is an indication that
the system is not in a state of equality (or natural strength); is measured by the power
difference between the initial and final state of the system in any particular case. In many
cases the apparent amount is not determined by the size of the ointment but by other
factors, which depend largely on the environment.
When we consider a common response group that involves involvement in slavery, we
will address as the first factors that determine the tendency of the material to adjust and
thus influence its initial resolution rate and as the second factors that influence the rate of
subsequent reaction. The word does not imply that the latter is insignificant; in fact, by
influencing the type and distribution of final corrosion products, they tend to determine
the final rate, as well as the useful life of the metal, in each area.
Under normal circumstances, one or two of the many factors involved have a positive
effect on the appearance of corrosion these we call controls or major features. Often, the
main features are related to the metal (or alloy) itself; second more features and specific
environment. It’s easy to separate them this way, even if no sharp differences can be
made. Some facilities offer the possibility of these chemical compounds and computer
equipment return to their low power levels.
Pure metals contain more bound energy, representing a higher energy state than that
found in the nature as sulphides or oxides.

9. Just as everything in the universe is struggling to regain its low energy levels, pure metals
are also struggling to return to their low energy levels, such as sulphides or oxides. One
of the ways materials can return to low energy levels is through corrosion. Iron corrosion
products are usually sulphides or oxide.
Corrosion Monitoring
Corrosion rates are described either by weight loss or by depth of penetration. Weight
loss has been most commonly given as milligrams of metal lost per square decimeter, but
many other metric, English have been used. The preferred metric (SI) unit is g·m−2
·d−1
.
Expressing corrosion as weight loss is only valid for uniform attack, since for localized
attack (such as pitting) the weight loss is meaningless.
Sometimes visual inspections are difficult in plant machinery and pipes, rust is often
checked with metal coupons embedded in the river. Coupons are also used in laboratory
and field tests to test various substances, defense holes, and inhibitors. Coupon testing is
a long-term measurement method that works, works in any environment, and is the most
widely accepted method worldwide. But it requires strong attention to sample preparation
and cleaning.
The Rate of Corrosion
The rate of corrosion is the speed at which any given metal deteriorates in a specific
environment.
Corrosion is one of the most important parameters used by engineers from design,
maintenance and mechanical support. For example usually we always use 3mm to allow
corrosion of carbon steel. But in some cases, the corrosion allowance will exceed 3mm,
due to the low level of waterlogging.
The level, or speed, depends on the natural conditions and the type and condition of the
material. Rust rates in the U.S. are generally calculated using mils per year. In other
words, the level of corrosion is based on the number of millimeters (thousands of inches)
that enter each year.
Methods for calculating Rate of Corrosion
There are three main methods that are used to express the corrosion rate:
• Thickness reduction of the material per unit time.
• Weight loss per unit area and unit time.
• Corrosion current density.

10. Thickness reduction per unit time is the measure of most practical significance and
Interest.
In order to calculate the rate of corrosion, the following information must be collected:
• Weight loss (the decrease in material weight during the reference time period)
• Density (density of the material)
• Area (total initial surface area of the material piece)
• Time (the length of the reference time period)
Corrosion determine the lifespan of steel-framed buildings. This flexibility controls the
selection of instruments used for different purposes, and in different locations. The
corrosion level also determines the maintenance requirements of the buildings.
It is found by:
R = d/t
expressed in µm/y but can also be expressed in terms of:
• Weight loss g/m2
• mg/dm2.day
The total amount of lost thickness in micrometers is: d = total.
Loss occurrence is t = time in years.
Corrosion rates are usually expressed as a penetration rate in “inches per year” or “melts
per year (MPY)” (where a melt = 10-3 inches).
This level may differ if the measure presented by the above function is used to compare
the rust values for a period of less than one year with values calculated over short
periods. This is because short-term prices are prone to fluctuations in seasonal changes
over the course of a season.
This method involves the disclosure of a piece of weight of material or heavy metals in a
particular area over a period of time. This is followed by careful cleaning to remove
corrosion products and determine the weight of the metal lost due to corrosion.
The (uniform) corrosion rate of steel in different atmospheres:

11. The degree of corrosion will depend on the temperature and concentration of the
corrosion liquid. Rising temperatures often result in higher rust levels. The level of
corrosion will also depend on other factors affecting all temperatures, such as oxygen
solubility and environmental conditions.
The effect of torturing a destructive medium is also complex. For example, the level of
corrosion of mild iron in refined sulfuric acid is unacceptably high. But on the other
hand, the level of corrosion of sulfuric acid combined by 70 percent is an acceptable
distance.
Types of Corrosion
1. Metallic Corrosion
• Uniform, or “general,” corrosion
• Dealloying
• Pitting
• Crevice
• Intergranular
• Filiform
• Corrosion by high-temperature gases
• Deposit-induced corrosion, which includes “hot corrosion”
• Galvanic corrosion
• Stress corrosion cracking
• Corrosion fatigue
• Fretting corrosion

12. • Tribo corrosion
• Erosion corrosion
• Hydrogen embrittlement, hydrogen-induced cracking, and hydrogen attack
Now we shall explain all of them
➢ Uniform Corrosion
Uniform corrosion is characterized by destructive attacks that spread evenly over the
entire surface, or a large part of the entire surface. Normal reduction occurs until it fails
.
The breakdown of protective coating systems on structures often leads to this form of
corrosion. Dulling of a bright or polished surface, etching by acid cleaners, or oxidation
(discoloration) of steel are examples. It can be controlled directly by cathodic protection,
the use of cloth or paint, or by specifying a corrosion allowance. In some cases rust
wearing a uniform adds color and more appeal.
Dealloying
Dealloying or selective leaching refers to the selective removal of one element from an
alloy by corrosion processes. or
Dealloying is the selective corrosion of one or more components of a solid solution alloy.
It is also called parting, selective leaching or selective attack.
Common dealloying examples are decarburization, decobaltification, denickelification,
dezincification, and graphitic corrosion.
Decarburization is the selective loss of carbon from the surface layer of a carbon-
containing alloy due to reaction with one or more chemical substances in a medium that
contacts the surface.

13. Decobaltification is selective leaching of cobalt from cobalt-base alloys, such as Stellite,
or from cemented carbides.
Denickelification is the selective leaching of nickel from nickel-containing alloys. Most
commonly observed in copper-nickel alloys after extended service in fresh water.
Dezincification is the selective leaching of zinc from zinc-containing alloys. Most
commonly found in copper-zinc alloys containing less than 85% copper after extended
service in water containing dissolved oxygen.
➢ Pitting Corrosion
This type of corrosion occurs when an anodic or cathodic point forms a rust cell with a
surrounding area. This pitt can form a hole or shell that often penetrates the mold to the
surface. It leads to the formation of small metal holes.
Pitting corrosion can be caused by damage or breakage to the oxide film or protective
coating and can be caused by uneven metal structure. This dangerous method of
corrosion can cause the structure to fail despite the loss of low-grade steel.
Pitting is considered to be more dangerous than uniform corrosion damage because it is
more difficult to detect, predict and design against. Corrosion products often cover the
pits.

14. Pitting corrosion is caused by the environment which may contain very strong chemical
species such as chloride. Chloride damages the passive film so pitting can initiate when
oxide breaks.
➢ Crevice Corrosion
This type of corrosion occurs in areas where oxygen is restricted, such as under washers
or heated heads. This home-made disclosure often results in differences in ion
concentrations between two metal surfaces. The static micro envelop blocks the flow of
oxygen, which prevents the re-passage and causes the formation of a moving solution that
moves the pH balance away from neutrality.
The imbalance between crevice and other uses contributes to high levels of rust. Crevice
corrosion can occur at lower temperatures .
Crevice corrosion is more rapid when chloride, sulfate or bromide ions are present in the
electrolyte solution.
Stainless steels, Aluminum alloys and other metals that form oxide layers that are not
found in their places in the professors and air are sensitive to corrosion.
Mechanism of crevice corrosion is similar to that of Pitting corrosion, dissolution of the

15. passivating film and gradual acidification of the electrolyte caused by its insufficient
aeration (Oxygen penetration).
Anodic reactions inside the crevice:
Fe = Fe2+
+ 2e-
(dissolution of iron)
The electrons given up by the anode flow to the cathode (passivated surface) where they
are discharged in the cathodic reaction:
1/2O2 + H2O + 2e-
= 2(OH-
)
As a result of these reactions the electrolyte enclosed in the crevice gains positive
electrical charge in contrast to the electrolyte surrounding the crevice, which becomes
negatively charged.
The positively charged electrolyte in the crevice attracts negative ions of chlorine
Cl-
increasing acidity of the electrolyte according to the reaction:
FeCl2 + 2H2O = Fe(OH)2 + 2HCl
PH of the electrolyte inside the crevice decreases (acidity increases) from 6 to 2-3, which
causes further acceleration of corrosion process.

16. ➢ Intergranular Corrosion
Intergranular corrosion occurs when impurities are present in grain boundaries that form
during the solidification of the alloy. It can also be caused by enrichment or reduction of
the material used in the cultivation at the limits of the grain. This type of rust occurs on or
near metal surfaces, affecting metal structures despite the amount of material being
unaffected.
Intergranular corrosion occurs when metal grain barriers form an anode and the inside of
the grain acts as a cathode. In extreme cases this can lead to the bullets falling to the
ground. This type of corrosion is a problem for non-ferrous metals, but it also occurs on
other metals.
In many cases of rust, including combined rust, the grain limits behave in the same way
as the grain itself. However, in some cases, grain restrictions may face local invasions
while the rest will not work. The alloy decomposes and loses its mechanical properties.
This type of rust is caused by contamination of the borders, or local enrichment or
reduction of one or more decorative elements.

17. ➢ Filiform Corrosion
Filiform, or under rust film is a type of corrosion known as "local" and is often
associated with magnesium and aluminum alloys using an organic coating type.
However, it is also possible for other composite metals such as iron, iron and zinc.
The filling system allows water and oxygen to move. Melted oxygen has a very high
impact. When oxygen is depleted in the tail region, dehydration and metal formation
go to the head. This type of corrosion has a tendency to occur in humid conditions.
Nitrates, sulfates, carbonates and condensates contain halides attached to film coating.
Filiform corrosion can occur in areas with temperatures above the room and at a
humidity level of 75%. In areas where overcrowding has occurred, there is the
appearance of plaque similarities formed under the composite.
The compound will shrink and look like grass formed by mole traps, due to the impact
of rust. The thread will then continue to reach points when the binding is no longer
active. There is a possibility of initiating filiform corrosion with multiple binding
systems.
Usually, the damage to the metal is not so great. However, it has a detrimental effect
on the appearance of cast iron.

18. ➢ Corrosion By high Temp. Gases.
Oxidation is the most common form of high temperature - almost all active metals and
alloys will add more than a certain temperature, leading to overheating, loss of
material and changes in body structure. Gaseous invasion is not limited to oxygen but,
in combination with sulfur gases, carbon oxides, nitrous oxides, halogens and many
other chemical reactions.
In addition, the burning of high temperatures is not limited to the gaseous phase -
solid ashes and salts that contribute to its degradation, with the erosion associated
with the removal of the scale. In the liquid phase, molten metals and molten salts
present their own unique challenges, resulting in more complex and environmental-
dependent corrosion.
Financially, high temperature rust is an important problem. Any element exposed to
high temperatures in an inert room is at risk. These include aerospace, energy, metal
processing, automotive, waste disposal and chemical repair industries, and many more
outside.
Climate testing with special high-temperature activities (for example where metal dust
is touched) is performed in outdoor areas, equipped with this type of testing.

19. ➢ Hot Corrosion
High-temperature heating is a form of filling that occurs in gas turbines, diesel
engines, furniture or other machinery mixed with hot gas containing certain
pollutants. Fuel sometimes contains vanadium compounds or sulfates that can form
nutrients during mixing with a low melting point. These molten liquids are highly
corrosive to stainless steel and other alloys that are prone to corrosion resistance and
high temperatures. Other high-temperature reactions include high thermal oxidation,
sulfidation and carbonization. High temperatures of oxidation and other types of
corrosion are commonly used in the Deal-Grove model to respond to deviation and
reaction processes.
➢ Galvanic Corrosion
This type of corrosion occurs when two different metals with physical or electrical
contact are introduced into electrolytes (such as salt water) or when the metal is exposed
to a different electrolyte concentration. When two metals are immersed together, known
as the galvanic pair the active metal (anode) works much faster than the fine metal
(cathode). The galvanic series identifies which steering instruments are faster, which is
useful when using a sacrificial anode to protect the structure from cracking.
It can be a metal (or both) metal in this couple that may or may not associate itself.

20. Corrosion of the anode will accelerate. Corrosion of the cathode will shock or stop.
Galvanic compounds are the basis of many corrosion detection techniques. The system
was also built on the useful protection of steel buildings by Sir Humphry Davy and
Michael Faraday in the early nineteenth century. A corrosion of single-metal corrosion
such as zinc, magnesium or aluminum is a comprehensive way to protect metal
structures.
The need for the two metals to be connected electrically so that galvanic corrosion would
occur when the magnificent metal passed slowly dissolved in water and flowed over the
less expensive metal. A more sophisticated metal may include non-ferrous metals, thus
becoming real bimetallic contacts. The current flow as a potential difference occurs
between two pieces of metal or between different parts of the same metal, and a moisture-
like electrolyte is present in the contact area.
The basic principles for the prevention of galvanic corrosion are:
1. Use of an insulating material between the dissimilar metals such that they are not in
direct electrical contact. This effectively breaks the electrical circuit so the current can
not flow.
2. Preventing the electrolyte from bridging across the two metals.

21. ➢ Stress Corrosion
The stress cracking refers to the growth of cracks due to the destructive nature that
can lead to the failure of ductile metals when pressed too hard, especially at high
temperatures. This type of corrosion is more common among alloys than pure metals
and relies on a specific chemical environment where only a small concentration of
active chemicals is required to break down the disaster.
Cold creation and construction, heating, heat management, machinery and milling can
bring residual pressure. The magnitude and significance of such pressures are often
underestimated. Residual pressure set due to welding performance is often close to
fruit strength. The construction of rust products in confined spaces can also cause
great stress and should not be overlooked. SCC usually arises from a combination of
certain pressures. It is caused by the combined influence of critical stress and the
destructive environment.
Usually, most of the surface remains untouched, but it has good links to the content.
In micro stage, these cracks may have trans granular morphology. Macroscopically,
SCC fractures look brittle. The SCC is classified as a catastrophic form of rust, as the
detection of this fine crack can be extremely difficult and the damage is not easily
predicted.

22. ➢ Corrosion Fatigue
Corrosion-fatigue is the result of the combined action of an alternating or cycling
stresses and a corrosive environment. The fatigue process is thought to cause rupture
of the protective passive film, upon which corrosion is accelerated. If the metal is
simultaneously exposed to a corrosive environment, the failure can take place at even
lower loads and after shorter time.
The process of fatigue is thought to cause the explosion of a protective film, in which
the rust is faster. If the metal is exposed simultaneously to the damaged area, failure
can occur at low loads and after a short time.
In the latter case, the level of thinking in which a healthy object can be considered to
be limited is reduced or eliminated altogether. In contrast to pure mechanical fatigue,
there is no burden to relieve fatigue in the aid of rust.
Corrosion fatigue and anxiety both in this class. Too much pressure of failure and too
short periods of failure can occur in a destructive environment compared to a situation
where alternating pressure is in a non-destructive environment.
Exhaustion is contaminated and cracks often transmit subtleties, such as the stress of
mental retardation, but which cannot be illuminated. The diagram shown here
illustrates the fragmentation of basic fatigue that has been exacerbated by certain
reactions of other compounds. The destructive environment can cause rapid growth
and / or boundary growth at a lower level of tension than in dry air.
Protection Possibilities Checklist
• Reduce or remove cyclic pressure.
• Reduce stress concentration or apply equal pressure on that object.
• Choose the correct structure for critical categories.
• Provide against rapid loading changes, temperature or pressure.
• Avoid internal pressure.
• Avoid the design or vibrations.
• Increase the natural frequency to reduce resonance corrosion fatigue.
• Limit the rust limit of the disability process (resistance / environmentally
friendly material).

23. ➢ Fretting Corrosion
Fretting corrosion is defined as the particular kind of damage which occurs when two
surfaces in contact experience slight periodic relative movement. Examples are cited
for their emergence in a wide variety of settings such as integrated structures and a
power switch. It can lead to loss of righteousness, or imprisonment, and can be a
source of exhaustion.
At the moment there is no clear indication that the appearance of cracks in sensitive
areas is due to holes designed to act as pressure cutters, or their condition can greatly
produce such an effect, even if conditions that produce sadness also cause surface
fatigue. The amount of injury increases almost directly in line with the relative height
of the movement associated with increasing the normal load. It also rises as the
temperature drops or as the atmosphere fills with rust.

24. ➢ Tribo Corrosion
Tribocorrosion is a material degradation process due to the combined effect
of corrosion and wear.
Tribocorrosion is a process of vandalism due to the combined effects of rust and wear.
Under these conditions, material selection is a challenge because materials have to deal
with wear, rust and their combined effect.
The importance of tribology and tribocorrosion is to know the mechanical failure due to
wear and tear. Potential savings in the industry by reducing repairs, downtime, cracks and
equipment replacement are available.
The application of best practices and well-known national policies can save industry and
society from this cost. Research within tribology contributes to increased efficiency and
availability of production processes, longer machine life and safer performance.

25. ➢ Erosion Corrosion
Erosion corrosion is an acceleration in the rate of corrosion attack in metal due to the
relative motion of a corrosive fluid and a metal surface. Erosion corrosion is the rapid
rate of attack of metal corrosion due to movement associated with corrosive liquid and
metal surface. Increased turbulence caused by throwing up the inside of the tube can lead
to an increase in erosion rates and ultimately leakage.
Erosion corrosion can be enhanced by improper operation. For example, holes left at the
edges of the tube can interfere with the smooth flow of water, causing chaos and areas of
high flow, leading to erosion. The combination of erosion and rust can lead to very high
levels of casting.
This occurs due to the speed of the moving fluid, as well as the destructive areas. It can
eat through any protective layers before continuing to damage the metal itself. Erosion
corrosion is most common in construction sites, those areas where there are blockages,
inlet enders, impellers pump, and other areas where there are high flow rates.
In many ways the erosion patterns of housing erosion can be reduced. The most obvious
way is to reduce the chaos by fixing the pipes. One can also try to slow down the flow of
fluid, since a small amount of fluid can cause a small disturbance.
Use corrosion inhibitors or cathodic protection can be a good way to protect pipes.
Reducing the amount of dissolved oxygen in the liquid will also help reduce erosion, as
well as adjust its pH value.
It would be better if you try to avoid erosion before installation during production, than to
try to reduce it afterwards. This can be done by calculating the costs and materials used to
deal with corrosion during the design and production phase.
It is also important to make sure that the entire pipeline system is removed before it can
start operating, as competitors can create local chaos.
In addition, make sure the system is kind rather than sharp angles will ensure there are a
few issues.

26. ➢ Hydrogen Embrittlement
This is a type of deterioration which can be linked to corrosion and corrosion-control
processes. It involves the ingress of hydrogen into a component. This is a type of
deterioration that can be linked to corrosion control procedures. It involves the fusion of
hydrogen in a particular component, an event that can significantly reduce the slope and
load-bearing capacity, resulting in a reduction and failure of the pressure brake
component in the lower part of the yield of non-working metals. Hydrogen constipation
occurs in many ways but the most common features are stress and dissolved hydrogen in
iron. Examples of hydrogen implants are fragmented where weldments or solid metals
are inserted when the conditions for hydrogen permeability are exposed. At present this
phenomenon is not fully understood and the detection of hydrogen bonding, in particular,
appears to be one of the most difficult aspects of the problem. Hydrogen absorption does
not affect all metal components equally. The weakest victims are high-strength showers,
titanium alloys and aluminum alloys.

27. Hydrogen may be produced by the effects of corrosion such as corrosion, cathodic
protection, and electroplating. Hydrogen can also be added to the reaction coolant to
remove oxygen from the cooling systems it uses. Hydrogen infiltration, a clear
prerequisite for authorization, can be done in many ways.
If the metal is under intense pressure, it may fail to form a stem. At normal room
temperatures, hydrogen atoms are placed in a metal part and then separated by grain,
which tends to accumulate in compacted areas or other dough markers. If the pressure
causes a crash under these conditions, the path passes. At higher temperatures,
concentrated hydrogen tends to accumulate at the edges of the grain, and the cracking
caused by the pressure then condenses. Cracking of martensitic and perception hardened
alloys is believed to be a form of hydrogen stress compression resulting from the
penetration of the atomic part of the atom produced in the subsequent corrosion reaction.
Hydrogen embrittlement is not a permanent condition. If a crash does not occur and
natural conditions change so that no hydrogen is produced on the metal, hydrogen can re-
emerge from the iron, so that the combustion energy is restored.

28. ➢ Microbial Corrosion
Microbial corrosion is a form of biodeterioration and is often referred to as biocorrosion
corrosion. This process of decomposition mainly applies to metals, metals, minerals, and
other materials. In addition to bacteria, fungi, microalgae, and naturally occurring
biological chemicals contribute to biocorrosion.
Now we will explain non metallic corrosion
2. Non Metallic Corrosion
• Recession of ceramics
• Radiolysis
• Acid-driven degeneration
• Metal-ion-induced oxidation
➢ Recession of Ceramics
Ceramics are non-constructive or composite solutions and these materials may have a
crystalline structure or a crystalline component, which decomposes to rust when
combined with solids, liquids, or gases, or any combination of these.

29. 1. Corrosion by solids
Crystalline materials undergo interdiffusion or the process of chemical reactions
when in contact with solids. The power of the intervention is due to the powerful
chemical technology, which causes the chemical reaction on the surface and leads to
the deterioration of the mud substance.
2. Corrosion by liquids
Liquid crystalline in liquids follows the methods of indirect decay, malfunction,
malfunction, or severe decay. The destructive environment with a liquid medium
contributes to an increase in medium speed, thus causing corrosion. Difficulty using
the boundary layer is considered as a measure to reduce the limit during demolition.
The structure of the boundary layer may vary depending on the size of the installation
across the ceramic boundary.
3. Corrosion by gases
When crystalline ceramic evaporates, it quickly penetrates into the material and
causes corrosion. Therefore, porosity volume and pore size are the most important
factors that control corrosion.
➢ Radiolysis
It is to be noticed that the more concentration of hydroxyl present in irradiated water in
the inner coolant loops of a light-water reactor must be taken into notice when designing
nuclear power plants, to prevent coolant loss resulting from corrosion. Otherwise there
will e huge loss for the plant.

30. ➢ Acid Driven Degeneration
Acid corrosion is the wearing away, or gradual destruction, of materials by acidic
compounds. Acids can arise from the atmosphere, soil or soil, and water is needed for
these outbreaks to continue. Acid metal corrosion is caused by electrochemical processes.
The term acid corrosion is also used extensively in climatic conditions, or decay,
processes that affect the stone (especially carbonate stone). There is a wide range of
processes for iron corrosion, but they usually require three conditions to be met: potential
differences should exist in areas where they are formed there must be a mechanism for
the transfer of funds between operators and a continuous mechanism of initiation must
exist between the cathodic and anodic centers.
Metal corrosion is usually treated with the addition of moisture, air and air pollutants.
Acids are, in general, mainly corrosive substances and cause the deterioration of surfaces
of many materials. However, not all acids are corrosive in nature. However, dilute
sulfuric acid will not be able to cause corrosion.

31. Corrosion Environment
Corrosion is a complete, natural process. If the water is seen rising and standing flowing
it will cause deterioration around where it was flowing, there may be reason to wonder.
Similarly, if iron or soft metal were exposed to water or wet air, mussel blasting (the first
type of iron oxide) is expected to develop within a few hours. In fact, it can be surprising
if the metal exposed is incorrect. Of course, if copper, brass, aluminum, or alloy resists
are added. Some oxides of copper, aluminum, and chromium usually form less and then
lower iron. Although very small, these gas coats can be a significant barrier to further
attack and reduce the level of corrosion almost to the level of the stairs.
The composition of the surface layer, whether it is based on oxide, carbonate, sulfate, or
something else, is a major factor in corrosion, especially if the layer separates the metal
layer well from the environment. Such natural combinations to be made must be varied-
and moisture resistant in order to be effective. Normal iron does not naturally form a
functional barrier; its corrosion allows oxygen and moisture to penetrate inside and
continue to rust. Therefore, unless precautionary measures are taken such as installing an
overprotective barrier, failure will eventually occur.
Some metals such as titanium, or aluminum, are often left untouched when exposed to the
atmosphere. This is not due to the fact that these metals are not installed, but because the
oxygen in the air helps to develop a protective oxide layer on the metal. Although these
oxide layers are usually too thin to be visible to the naked eye, they can be detected and
their presence confirmed.
Some areas are more corrupt than others. Despite the exceptions, the following
statements are generally accepted as fact
Moreover
• Moist air will do more damage than dry air.
• Hot air is more corrosive than cold air.
• Polluted air is more harmful than clean air.
• Hot water is more corrosive than cold water.
• Salt water is more corrosive than fresh (low chloride content) water.

32. Prevention Of Corrosion
We can’t stop corrosion but we can do that the corrosion can be managed, slowed, or
even stopped by using the proper techniques. Corrosion prevention can take a number of
forms depending on the circumstances of the material which is being corroded.
➢ Metal Selection and Surface Conditions
No material is resistant to corrosion in any type of environments, but through monitoring
and taking into consideration the environmental conditions that are the cause of
corrosion, changes to the type of metal being used can also lead to significant reductions
in corrosion process.
Material corrosion resistance data can be used in combination with information on the
environmental conditions to make decisions regarding the suitability of each metal.
➢ Cathodic Protection
Cathodic protection works by converting unwanted anode (active) over the metal sites
into cathodic (passive) sites through the current opposition. This current resistance
provides free electrons and forces local anodes to be separated by area codes.
Cathodic defense can take two approaches. The first is the introduction of galvanic
anodes. This method, known as a devotional system, uses a metal anode, introduced into
the electrolytic environment, a self-corroding (corrode) to protect the cathode.
The second method of cathodic protection is referred to as impressive current protection.
This method, often used to protect buried pipes and tankers, requires another specific
power source to be supplied with electrolyte.
➢ Inhibitors
Corrosion inhibitors are chemicals related to metal surfaces or natural inhibitors that
cause corrosion, thus, disrupting the chemical reaction that causes corrosion.
Inhibitors can work by attaching themselves to the metal surface and forming a protective
film. These chemicals can be applied as a solution or as a preventive measure by
dissemination techniques.
➢ Coatings
Paints and other organic coatings are used to protect metals from the deteriorative effect
of atmospheric gases. Coatings are classified by the type of polymer employed. Common
coatings include:

33. • Alkyl and epoxy ester coatings that, when air dried, promote cross-link oxidation
• Two-part urethane coatings
• Both acrylic and epoxy polymer radiation curable coatings
• Vinyl, acrylic or styrene polymer combination latex coatings
• Water-soluble coatings
• High-solid coatings
• Powder coatings
➢ Plating
Metallic coatings, or plating, can be applied to reduce the corrosion as well as provide
aesthetic, decorative finishes and proper finishing. There are four common types of
metallic coatings:
• Electroplating: A thin layer of metal - often nickel, tin, or chromium - is
deposited on the substrate metal (generally steel) in an electrolytic bath. The
electrolyte usually consists of a water solution containing salts of the metal to be
deposited.
• Mechanical Plating: Metal powder can be cold welded to a target material by
tumbling the part, along with the powder and glass beads and dine in a treated
aqueous solution.
• Electroless: A coating material, is deposited on the target material using a
chemical reaction in this non-electric plating method.
• Hot Dipping: When immersed in a molten bath of the protective, coating metal a
thin layer sticks to the target material.
➢ Environmental Modification
Corrosion is caused by chemical interactions between material and in the environment.
By removing the material form, or replacing, the natural type, the corrosion of the
material can be quickly reduced.
This can be as simple as limiting contact with rain or sea water by keeping metal objects
inside or it can be a way to use the environment directly affecting the metal.
Ways to reduce sulfur, chloride, or oxygen content in the environment may reduce the
rate of metal corrosion. There are many inexpensive ways to prevent rust including
• Use non-corrosive metals, such as stainless steel or aluminum.
• Make sure the metal plate stays clean and dry.

34. • Use drying agents.
• Use a blending or blending product such as lubricant, oil, paint or carbon fiber
coating.
• Lay a retrospective layer, for example, limestone, through an underground pipe.
• Use the sacrificial anode to provide a cathodic protection system.
➢ Natural protection
Some metals experience natural passivity, or corrosion resistance. This occurs when
material gathers in with the oxygen in the air. The result is a thin film of oxide that blocks
the tendency of the metal to make another reaction.
The patina that forms the brass and the air in some objects to know are examples of this.
Protection fails if the thin film is damaged or damaged by structural pressures on the
bridge, for example or by photography or writing. In such cases the material can
duplicate, but if that does not happen, only parts of the object code. After that the
corrosion is usually worse because the focus is on these sites.
Conclusion
Corrosion is a natural process that leads to the deterioration of building materials which,
if unprotected, leads to the ultimate destruction of material. Significant progress has been
made in the development of anti-corrosion materials, the understanding of the underlying
mechanisms of corrosion, and the development of mitigation strategies.
This progress has allowed the current state of resource use in both conventional and non-
violent environments. Since most of the world's population live near water and moisture,
the emergence of metal objects has become an inevitable part of human experience.
The effects of rust are often described in terms of economic factors. Financial losses have
been assessed in numerous studies that found that premature destruction of industrial
assets cost industrialized nations about 3 percent of their gross domestic product (GDP).
$ 2 trillion and $ 4 trillion are lost every ten years to some extent.
Corrosion can also affect public health, the environment, and global sustainability in
ways that cannot be explained by GDP losses. The deterioration of the first-generation
medical device and the replacement of implants from contact with human body moisture,
the installation of burglary products in the environment, and the weakening of the
country's ability to combat the construction of state vehicles have all far outweighed the
financial implications.

35. References
1. [Fundamentals of corrosion – Mechanisms, Causes and Preventative Methods]. Philip A.
Schweitzer, Taylor and Francis Group, LLC (2010), p. 25.
2. Fontana, M. G., Corrosion Engineering, McGraw-Hill, New York (1987).
3. Corrosion of Glass, Ceramics and Ceramic Superconductors. D.E. Clark, B.K. Zoitos (eds.),
William Andrew Publishing/Noyes (1992)
4. Historic Congressional Study: Corrosion Costs and Preventative Strategies in the United
States, a Supplement to Materials Performance, NACE International, Houston TX (July
2002)
5. W. Wallace, D. W. Hoeppner, and P. V. Kandachar, AGARD Corrosion Handbook, Volume
1, Aircraft Corrosion: Causes and Case Histories, Advisory Group for Research and
Development, AGARD-AG-278 Vol 1; DTIC Doc.: AD-A160 638
6. Handbook of Corrosion Data, 2nd Edition, Eds. B. D. Craig and D. S. Anderson, ASM
International, 1995.
7. R. C. Bill, “Review of Factors That Influence Fretting Wear”, Materials Evaluation Under
Fretting Conditions, ASTM STP 780, American Society for Testing and Materials, 1982, pp.
165-182.