Corrosion is the deterioration of metals due to chemical or electrochemical reactions with their environment. There are several types of corrosion including general corrosion, pitting corrosion, intergranular corrosion, stress corrosion, crevice corrosion, galvanic corrosion, erosion corrosion, cavitation corrosion, and fretting corrosion. The document discusses the causes and characteristics of each type. Corrosion can be prevented by selecting the proper metal type, protective coatings, environmental controls, sacrificial anodes, corrosion inhibitors, and design modifications. Surface pretreatments and coatings are important for inhibiting corrosion.
A brief introduction to corrosion and types of corrosion, such as pitting corrosion.
Cavitations corrosion
Galvanic corrosion.
Fretting corrosion.
Crevice corrosion.
Intergranular and transgranular corrosion,
Stress corrosion
Corrosion is a natural process, which converts a refined metal to a more chemically-stable form, such as its oxide, hydroxide, or sulfide. It is the gradual destruction of materials (usually metals) by chemical and/or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and stopping corrosion.
A brief introduction to corrosion and types of corrosion, such as pitting corrosion.
Cavitations corrosion
Galvanic corrosion.
Fretting corrosion.
Crevice corrosion.
Intergranular and transgranular corrosion,
Stress corrosion
Corrosion is a natural process, which converts a refined metal to a more chemically-stable form, such as its oxide, hydroxide, or sulfide. It is the gradual destruction of materials (usually metals) by chemical and/or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and stopping corrosion.
This topic includes various aspects regarding Corrosion prevention. It includes material of construction, how environment changes and its effect on corrosion, how can we properly design our equipment to avoid from corrosion. It also includes Cathodic protection and Anodic protection.
Video lecture is available on YouTube on the link:https://youtu.be/xrBnxxN-RUw
For UG students of All Engineering Branches, Chemistry, Food Science, Polymer Science, Chemical Engg. etc.
This topic includes various aspects regarding Corrosion prevention. It includes material of construction, how environment changes and its effect on corrosion, how can we properly design our equipment to avoid from corrosion. It also includes Cathodic protection and Anodic protection.
Video lecture is available on YouTube on the link:https://youtu.be/xrBnxxN-RUw
For UG students of All Engineering Branches, Chemistry, Food Science, Polymer Science, Chemical Engg. etc.
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.
Corrosion is a natural process that deteriorates materials, commonly metals, due to chemical or electrochemical reactions with their environment. It's a significant concern across various industries, including infrastructure, manufacturing, and transportation. The effects of corrosion can range from minor aesthetic damage to catastrophic structural failure, leading to enormous economic costs and safety hazards.
Several factors influence corrosion, including environmental conditions such as moisture, temperature, pH levels, and the presence of corrosive agents like oxygen, sulfur compounds, and salts. Additionally, the material's composition and microstructure play crucial roles in its susceptibility to corrosion.
To mitigate corrosion and prolong the lifespan of materials, various protection methods are employed:
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.
Each protection method has its advantages and limitations, and the choice of method depends on factors such as the material, the environment, cost considerations, and the required durability. In many cases, a combination of protection methods may be employed to provide optimal corrosion resistance.
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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3. • Corrosion is 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.
• Deterioration or destruction of metals and
alloys in the presence of an environment by
chemical or electrochemical means.
• Corrosion can be viewed as a universal
phenomenon, omnipresent and omnipotent.
4. Some of the major harmful effects of
corrosion are:
• Nuclear plant shutdown due to failure, for example, nuclear reactor during decontamination
process.
• Replacement of corroded equipment resulting in heavy expenditure.
• High cost preventive maintenance such as painting.
• Loss of efficiency.
• Loss of product from a corroded container.
• Safety requirement measures from a fire hazard or explosion or release of toxic product.
• Health problems, for example, drinking water contamination with lead is likely due to
corrosion.
5. Corrosion has been classified into 3
different methods
1. Low temperature corrosion and high temperature
corrosion
2. Electrochemical corrosion and chemical corrosion
3. Wet and Dry corrosion.
6. Wet corrosion occurs when the metal
is in contact with an electrolytic conducting
liquid or when two dissimilar metals or
alloys are either immersed or dipped
partially in the electrolytic conducting
solutions. This is always associated with
low temperature conditions.
7. The corrosion process involves
two reactions
1. Anode
M (metal) → Mn+ + ne− (oxidation)
Mn + (metal ion) → Dissolves in
solution
Mn + (metal ion) → Forms
compound such as oxide
2. Cathode
2H+ + 2e− → H2↑ (in acid solution)
2H2O + 2e− → H2↑ + 2OH− (in
alkaline solution)
O2 + 2H2O + 4e− → 4OH− (in
neutral solution)
8. Dry corrosion takes place mainly
through the direct chemical action of
atmospheric gases and vapors present in
the environment. This is most often
associated with high temperature.
10. 1. General corrosion
This general corrosion also called as a uniform attack is the most common
form of corrosion. It is normally characterized by a chemical or electrochemical
reaction which proceeds uniformly over the entire exposed surface or over a large
area. The metal becomes thinner and eventually fails.
Intrinsic – Independ of Design configuration
11. 2. Pitting corrosion or localized corrosion
Pitting corrosion is a localized attack resulting in the formation of holes in the
metals. These holes are relatively small and they are looks like a rough surface, they
were sometimes isolated or so close together. Pitting is one of the most destructive
and insidious forms of corrosion.
Intrinsic – Independ of Design configuration
12. 3. Intergranular corrosion
Also known as intergranular attack, is a form of corrosion where the
boundaries of crystallites of the material are more susceptible to corrosion than
their insides.
Intrinsic – Independ of Design configuration
13. 4. Stress corrosion
The cracking of metal or alloy by the combined action of a tensile stress and a
corrodent is known as stress corrosion cracking. The susceptibility to stress corrosion
cracking is due to certain metallurgical factors such as, Chemical composition,
Preferential orientation of grains, Composition and distribution of precipitates, and
Dislocation structure and environmental factors and structure of metal.
Intrinsic – Independ of Design configuration
14. 5. Crevice corrosion or deposit corrosion
This kind of corrosion is attacked generally within crevices associated with
small volumes of stagnant solution trapped in holes, surfaces, joints and crevices
under bolt and rivet heads. It is also known as deposit or gasket corrosion.
Extrinsic – Depends of Design configuration
15. 6. Galvanic corrosion
It occurs when a potential difference exists between two dissimilar metals
immersed in a corrosive solution. This potential difference produces a flow of
electrons between the metals. Several investigations have shown that, galvanic
corrosion is directly proportional to the area of the cathodic to the anodic metal
Extrinsic – Depends of Design configuration
16. 7. Erosion corrosion
It is the increase of attack of a metal because of relative movement between a
corrosive medium and the metal surface. This type of erosion corrosion is usually
associated with systems where high velocities of corrosive fluids or gases are
encountered. This corrosion can be observed in piping system such as bends, elbows,
pumps, condensers, etc.
Extrinsic – Depends of Design configuration
17. Cavitation's corrosion
It is a special type of erosion corrosion which is caused due to the formation of
vapor bubbles in a corrosive environment near a metal surface and when the bubbles
collapse, attack arises for example, hydraulic turbulence, ship propellers, etc. It is similar
to pitting corrosion but the surface is rough and has many close spaced pits
18. 8. Fretting corrosion
Fretting is a wear phenomenon enhanced by corrosion. It involves wear of
a metal or alloy when in contact with another solid material in dry or humid air.
Fretting is the result of abrasive wear surface oxide films, which form a
contacting surfaces under load in atmospheric air .
The factors which affect fretting corrosion are:
• Magnitude of relative motion
• Temperature
• Environment
• Metallurgical factors
Extrinsic – Depends of Design configuration
19. 9. Corrosion fatigue
It is defined as, “the reduction of the fatigue strength due to the presence of
corrosive environment”. Corrosion fatigue occurs due to the combined action of
tensile and compressive stress alternatively. Fatigue occurs at lower stress in
corrosive environment.
Extrinsic – Depends of Design configuration
20. You can prevent corrosion by selecting the
right:
• Metal Type
• Protective Coating
• Environmental Measures
• Sacrificial Coatings
• Corrosion Inhibitors
• Design Modification
21. Corrosion Inhibition
A comprehensive review of corrosion inhibition on various metals and alloys
using either inorganic or organic pretreatment methods has been presented. Surface
pretreatment coatings, whether they are inorganic or organic, serve as the first line
of defense in inhibiting corrosion.
The selection of the proper pretreatment coating is essential in providing basic
corrosion protection for the underlying metal or alloy and promoting adhesion and
compatibility between the pretreatment and primer coating.