POWER ENGINEERING 2A2 FINAL PAPER 2026
COMPLETE QUESTIONS ANSWERS
◉ What is erosion corrosion? Answer: It involves the constant
repetitive creation and destruction of the protective surface film on
the metal.
If flow exceeds a critical velocity then the protective film is removed
and corrosion rates increase. When flow drops the protective film is
reestablished.
◉ Where does flow accelerated corrosion happened and what is the
cause? Answer: It happens when there is a change in direction or
other disturbances in flow.
It happens when feedwater has been totally dearated and the oxygen
level is very low. Low oxygen level doesn't allow the protective layer
of magnetite to form. Iron continuously is extracted trying to
establish the magnetite layer and the metal thins.
◉ Why is microbiological influenced corrosion a concern? Answer:
Microbes can cause corrosion or accelerate many of the other
corrosion mechanisms.
,◉ What are the four environmental conditions that must exist (along
with bacteria) for bacteria to grow and influence corrosion? Answer:
A metal surface to host the bacteria
Nutrients to feed the bacteria
Water
Oxygen
◉ What are the three types of bacteria of interest in corrosion?
Answer: Aerobic Bacteria - Need oxygen
Anaerobic Bacteria - Does not need oxygen
Facultative Bacteria - Can grow with or without oxygen
◉ What is atmospheric corrosion? Answer: Corrosion of a metal
surface when exposed to air and its pollutants.
◉ What are the three categories of atmospheric corrosion? Answer:
Dry atmospheric corrosion
Damp atmospheric corrosion
, Wet atmospheric corrosion
◉ How can dry atmosphere cause corrosion? Answer: It's a slow
process but oxygen in the air combines with iron in the metal.
◉ How are damp and wet atmospheric corrosion the same? How are
they different? Answer: Same - Moisture collects on the surface and
acts as an electrolyte.
Different - In damp conditions the moisture is invisible. In wet
conditions it is visible.
◉ What is a pollutant in the atmosphere that can accelerate
corrosion in atmospheric corrosion? Answer: Sulphur. This can be
more intense in industrial areas
◉ What is the most destructive type of stray current in stray current
corrosion? Answer: DC current
◉ What is a source of stray DC current corrosion? Answer: Welders
and improperly installed cathodic protection
◉ What is a source of stray AC current corrosion? Answer: Buried
power lines
COMPLETE QUESTIONS ANSWERS
◉ What is erosion corrosion? Answer: It involves the constant
repetitive creation and destruction of the protective surface film on
the metal.
If flow exceeds a critical velocity then the protective film is removed
and corrosion rates increase. When flow drops the protective film is
reestablished.
◉ Where does flow accelerated corrosion happened and what is the
cause? Answer: It happens when there is a change in direction or
other disturbances in flow.
It happens when feedwater has been totally dearated and the oxygen
level is very low. Low oxygen level doesn't allow the protective layer
of magnetite to form. Iron continuously is extracted trying to
establish the magnetite layer and the metal thins.
◉ Why is microbiological influenced corrosion a concern? Answer:
Microbes can cause corrosion or accelerate many of the other
corrosion mechanisms.
,◉ What are the four environmental conditions that must exist (along
with bacteria) for bacteria to grow and influence corrosion? Answer:
A metal surface to host the bacteria
Nutrients to feed the bacteria
Water
Oxygen
◉ What are the three types of bacteria of interest in corrosion?
Answer: Aerobic Bacteria - Need oxygen
Anaerobic Bacteria - Does not need oxygen
Facultative Bacteria - Can grow with or without oxygen
◉ What is atmospheric corrosion? Answer: Corrosion of a metal
surface when exposed to air and its pollutants.
◉ What are the three categories of atmospheric corrosion? Answer:
Dry atmospheric corrosion
Damp atmospheric corrosion
, Wet atmospheric corrosion
◉ How can dry atmosphere cause corrosion? Answer: It's a slow
process but oxygen in the air combines with iron in the metal.
◉ How are damp and wet atmospheric corrosion the same? How are
they different? Answer: Same - Moisture collects on the surface and
acts as an electrolyte.
Different - In damp conditions the moisture is invisible. In wet
conditions it is visible.
◉ What is a pollutant in the atmosphere that can accelerate
corrosion in atmospheric corrosion? Answer: Sulphur. This can be
more intense in industrial areas
◉ What is the most destructive type of stray current in stray current
corrosion? Answer: DC current
◉ What is a source of stray DC current corrosion? Answer: Welders
and improperly installed cathodic protection
◉ What is a source of stray AC current corrosion? Answer: Buried
power lines
