PRINCE MUHAMMAD BIN FAHD UNIVERSITY
MECHANICAL ENGINEERING DEPARTMENT
MEEN 4341 – CORROSION ENGINEERING
Spring 2024
S. No.
Student Name
Student ID
1
Mohammed AlGusaier
202000715
2
Yousef Alshammary
202001998
3
Mohammed Alkudair
202001790
4
Yousif Alhumaidan
202001653
Group Members
5
Section #
101
Homework #
3
Department
Mechanical Engineering Department
Instructor Name
Dr. Muhammad Azhar Ali Khan
Date
29th April 2024
MEEN 4341-Corrosion Engineering
Instructor: Dr. Muhammad Azhar Ali Khan
Q1:
Spring 2024
Submission Deadline: 29 April 2024
th
(a) What do you understand by uniform/general corrosion?
(b) Explain the difference between dry, damp and wet atmospheres with respect to
uniform corrosion.
(c) How can we control the uniform corrosion?
A)
Uniform or general corrosion is a type of corrosion that occurs evenly
across a metal surface. This form of corrosion results in a consistent and
predictable loss of material, often characterized by a dulling or tarnishing of
the metal surface.
B)
Dry Atmospheres: These contain little to no moisture, leading to slower
corrosion rates as water is a main component for many corrosion reactions.
Damp Atmospheres: In these conditions, the presence of moisture, often in
the form of humidity, can accelerate corrosion, especially if there are
pollutants like sulfur dioxide which can form weak acids on the metal
surface.
Wet Atmospheres: These environments are characterized by high moisture
levels, including rain or direct contact with water, greatly accelerating
corrosion rates due to increased availability of water to participate in
electrochemical reactions.
C)
Material Selection
Protective Coatings
Cathodic Protection
Environmental Control
MEEN 4341-Corrosion Engineering
Instructor: Dr. Muhammad Azhar Ali Khan
Spring 2024
Submission Deadline: 29 April 2024
th
Q2: (a) Can magnesium be used instead of zinc to cathodically protect steel in seawater? (b) Can
aluminum protect steel? (c) Refer to the galvanic series for seawater and select one additional
metal or alloy which can be used to cathodically protect steel.
A)
Yes, magnesium can be used as it is more active than zinc and provides
stronger protection in seawater.
B)
Yes, aluminum can be used as a sacrificial anode to protect steel,
particularly in less corrosive environments.
C)
Zinc is commonly used to protect steel in seawater due to its more negative
potential in the galvanic series.
MEEN 4341-Corrosion Engineering
Instructor: Dr. Muhammad Azhar Ali Khan
Spring 2024
Submission Deadline: 29 April 2024
th
Q3: In Case A below, two steel plates are joined with a Monel bolt. In Case B, the reverse is done.
Both systems are to be immersed in seawater, for which
E (steel) = –0.61 V
E (Monel) = –0.08 V.
Thus, there is a galvanic effect in which the steel member of the couple will be attacked. In Case
A, the steel plates will be galvanically attacked. In Case B, the steel bolt which keeps them together
will be galvanically attacked. One case is much worse than the other. Which case is it? Why?
Case B is much worse because the small steel bolt (anode) corrodes
rapidly due to its smaller area compared to the large Monel plates
(cathode). This rapid corrosion can lead to early structural failure.
MEEN 4341-Corrosion Engineering
Instructor: Dr. Muhammad Azhar Ali Khan
Spring 2024
Submission Deadline: 29 April 2024
th
Q4: For a metallic coating of type 430 stainless steel on mild steel, what happens if an imperfection
or a break develops in the coating, as shown below? Hint: Use the concept of galvanic corrosion
to answer this question.
If an imperfection occurs in the 430 stainless steel coating on mild steel, the
exposed mild steel will corrode rapidly due to galvanic corrosion, with
stainless steel acting as the cathode.
MEEN 4341-Corrosion Engineering
Instructor: Dr. Muhammad Azhar Ali Khan
Spring 2024
Submission Deadline: 29 April 2024
Q5: List at least five methods of protection against Galvanic Corrosion.
1. Use identical metals for all components.
2. Employ insulating barriers.
3. Use sacrificial anodes.
4. Implement cathodic protection.
5. Control environmental conditions.
th
MEEN 4341-Corrosion Engineering
Instructor: Dr. Muhammad Azhar Ali Khan
Spring 2024
Submission Deadline: 29 April 2024
th
Q6: In what ways are crevice corrosion and pitting similar? In what ways are they different?
Similarities:
Both are forms of localized corrosion.
Both can lead to severe metal damage despite minimal overall material loss.
Differences:
Crevice Corrosion: occurs in confined spaces where stagnant solution is present.
Pitting Corrosion: involves the formation of small holes or pits on the metal surface
without the need for a confined space.
MEEN 4341-Corrosion Engineering
Instructor: Dr. Muhammad Azhar Ali Khan
Q7:
Spring 2024
Submission Deadline: 29 April 2024
th
(a) What are the conditions which favors pitting?
(b) Explain the two stages i.e. initiation and propagation in pitting corrosion?
A)
Presence of chloride ions.
High temperatures.
Low pH (acidic conditions).
Presence of oxidizing agents.
Metal surface imperfections.
B)
Initiation: Occurs at surface defects where passive film breaks down,
usually by chlorides.
Propagation: The pit deepens and widens as the local anodic area
corrodes, with the environment inside becoming increasingly acidic,
accelerating corrosion.
MEEN 4341-Corrosion Engineering
Instructor: Dr. Muhammad Azhar Ali Khan
Q8:
Spring 2024
Submission Deadline: 29 April 2024
th
(a) How can we control crevice corrosion?
(b) What do you understand by filiform corrosion?
A)
Use non-absorbent materials.
Eliminate design features that create crevices.
Apply protective coatings.
Use corrosion-resistant alloys.
Maintain dry environments.
B)
Filiform corrosion is a type of corrosion that occurs under thin coatings,
such as paint or lacquer, on metallic surfaces. It appears as thread-like or
filamentous traces, usually initiated by a small defect in the coating, and it
spreads beneath the surface coating in humid conditions.
MEEN 4341-Corrosion Engineering
Instructor: Dr. Muhammad Azhar Ali Khan
Q9:
Spring 2024
Submission Deadline: 29 April 2024
th
(a) Explain sensitization with reference to the figure shown below.
(b) How intergranular corrosion can be controlled?
A)
The figure shows sensitization in stainless steel, where chromium carbides
form at grain boundaries, creating adjacent chromium-depleted zones. This
reduction in chromium impairs corrosion resistance, leading to intergranular
corrosion as shown in part (b) of the figure.
B)
Use low-carbon stainless steel.
Apply solution annealing.
Avoid exposure to temperatures between 450°C and 850°C.
Use stabilizing elements like titanium or niobium.
MEEN 4341-Corrosion Engineering
Instructor: Dr. Muhammad Azhar Ali Khan
Spring 2024
Submission Deadline: 29 April 2024
th
Q10: Explain the following terms related to flow assisted corrosion.
(a) Erosion-Corrosion
(b) Cavitation
(c) Fretting
A)
Erosion-corrosion is a type of corrosion accelerated by fluid flow, which mechanically
wears away the protective film on a metal's surface, exposing it to corrosive
processes.
MEEN 4341-Corrosion Engineering
Instructor: Dr. Muhammad Azhar Ali Khan
Spring 2024
Submission Deadline: 29 April 2024
th
Q11: In each of the figures below, identify the type of corrosion.
uniform corrosion
______________________
_______________________
intergranular corrosion
_______________________________
fretting corrosion
_____________________
errosion corrosion
pitting corrosion
________________________________
______________________________
crevice corrosion
atmospheric corrosion
___________________________
________________________
pitting corrosion
MEEN 4341-Corrosion Engineering
Instructor: Dr. Muhammad Azhar Ali Khan
Spring 2024
Submission Deadline: 29 April 2024
th
Q12: Read the review paper titled as “A REVIEW ON CORROSION OF METALS AND
PROTECTION” uploaded with HW 3 and answer the following question.
Iron and steel corrosion rates can vary with different environments and factors. Explain the
dependence of iron and steel corrosion on
(i) Aqueous Environment
(b) Metallurgical Factors
(c) Atmosphere
i. Contains metal ions they play a big role in forming corrosive produces.
ii. Corrosions of steel and iron is highly dependent on the surface condition
of the piece. The reason is many natural waters we can get from earth
good examples of electrolytes.
iii. Steel and iron are mostly exposed to the atmosphere than to any other
corrosion accelerating medium.