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Corrosion

Corrosion involves physical and chemical reactions between a metal, an electrolyte, and an oxidizing environment. Some key factors that influence the corrosion process are temperature, solute concentration, and the formation of a protective oxide film. Pitting corrosion is a localized and accelerated form of attack. Galvanic, pitting, and crevice corrosion are all difficult to monitor and can be very dangerous. Electrochemical corrosion occurs on anodic areas near the cathode. The corrosion process is enhanced by factors like air, moisture, electrolytes, and gases such as CO2 and SO2.

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Mus'ab Usman
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317 views5 pages

Corrosion

Corrosion involves physical and chemical reactions between a metal, an electrolyte, and an oxidizing environment. Some key factors that influence the corrosion process are temperature, solute concentration, and the formation of a protective oxide film. Pitting corrosion is a localized and accelerated form of attack. Galvanic, pitting, and crevice corrosion are all difficult to monitor and can be very dangerous. Electrochemical corrosion occurs on anodic areas near the cathode. The corrosion process is enhanced by factors like air, moisture, electrolytes, and gases such as CO2 and SO2.

Uploaded by

Mus'ab Usman
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOCX, PDF, TXT or read online on Scribd
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Corrosion of metals involves

Physical reactions
Chemical reactions
Both
None

The following factors play vital role in corrosion process


Temperature
Solute concentration
Both
None

Passivity is due to
Higher EMF
Lower EMF
Oxide film
All

Difficult to monitor and very dangerous form of corrosion


Galvanic
Pitting
Crevice
Stress

What is meant by corrosion?

Chemical reaction between anode, cathode and electrolyte, which leads to loss of metal
Deterioration of metals due to reaction with its environment
Both a. and b.
None of the above

Which type of chemical reaction is observed at cathode, in electrochemical corrosion?

Oxidation reaction
Peretectic reaction
Reduction reaction
None of the above
Lower is PH, corrosion is,

Greater

Lower

Constant

None of above

Electrochemical corrosion takes place on,

Anodic area

Cathodic area

Near cathode

Near anode

Process of corrosion enhanced by,

AIR & Moisture

Electrolytes in water

Metallic impurities

Gases like CO2 & SO2

All

Pitting corrosion is a __________ accelerated attack.

Non-localized

Localized

Diverse

None of above

In galvanic series, a metal high in series is more _________.

Anodic
Cathodic
Corroded
None f above
Acidic media are more corrosive than _________ and neutral media.

Less acidic
Alkaline
Inert
Non reactive

Destruction of metal starts ________.

At the surface
Just on layer below from surface
In the middle
At the bottom

Anodic reaction involves dissolution of metal as corresponding metallic ions with liberation of
_______.
.
Pair of electron
Free electron
Ions
Current in electrolytic solution

Evolution of hydrogen type corrosion occurs in _______ environment.

Acidic
Neutral
Basic
Alkaline

The rusting of iron is catalyzed by which of the following?

Iron
Oxygen
Zinc
H+

Conversion of Fe to Fe2+ is,


Oxidation.
Reduction.
Corrosion.
None of above

Which one is the wrong anode-cathode combination


Zinc-Iron
Nickel-Titanium
Iron-Tin
Silver-zinc

The metals which do not form adherent oxide film on surface are
Gold and Silver
Iron and Steel
Copper and Aluminium
Nickel and Titanium

The corrosion by the mechanism of oxygen absorption can occur if


Electrolyte is neutral or alkaline
Electrolyte is neutral or acidic
Electrolyte is neither neutral and nor acidic
None of the above

The potential of a galvanic cell of copper (potential of +0.34 Volt) and aluminium (potential of –
1.66 Volt) is
+1.5 Volt
+1.66 Volt
–1.32 V
+2 Volt

Aluminium exposed to air will

Oxidise and become weaker

Oxidise and become electrically neutral

Oxidise and become stronger

The main element in Monel(alloy) is

Aluminium

Nickel

Chromium

Iron

What corrosion occurs under organic coatings on metals as fine, wavy hairlines?

Stray current corrosion


Microbiological corrosion

Filiform corrosion

Fretting corrosion

What is defined as a local corrosion damaged characterized by surface cavities?

Cracking

Pitting

Cavitation

Erosion

What refers to the removal of zinc from brasses?

Dezincification

Graphitization

Stabilization

Dealloying

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