250+ TOP MCQs on Modern Theory Applications – Predicting Corrosion Behavior and Answers

Corrosion Engineering Questions on “Modern Theory Applications – Predicting Corrosion Behavior”.

1. Which of the following is/are the applications of mixed-potential theory?
a) Permit prediction of complex corrosion behavior
b) To develop new corrosion prevention methods
c) To develop new rapid corrosion rate measurement
d) Permit prediction of complex corrosion behavior, to develop new corrosion prevention methods and to develop new rapid corrosion rate measurement

Answer: d
Clarification: Applications of the mixed-potential theory are:

• Permit prediction of complex corrosion behavior
• To develop new corrosion prevention methods
• To develop new rapid corrosion rate measurement.

2. Which of the following is/are correct when oxidizing agents are added to a corrosion system containing a non-passivating metal?
a) Rate of corrosion decreases after certain potential
b) Rate of corrosion increases with increase in oxidizers concentration
c) Rate of corrosion increases after certain potential
d) Results in the formation stable oxide layer

Answer: b
Clarification: The rate of corrosion increases with increase as the concentration of oxidizing agents containing non-passivating metal. It is due to the reduction of oxygen on the surface of the metal and due to the absence of an oxide layer.

3. The corrosion rate is usually dependent at low velocity whereas at high velocities it becomes independent.
a) True
b) False

Answer: a
Clarification: Corrosion rate is usually dependent at low velocities whereas at high velocities it becomes independent. It is due to enough availability of ions at the interface and thereby it depends on activation energy.

4. Which of the following type of polarization has a negligible effect on velocity?
a) Concentration polarization
b) Activation polarization
c) Concentration polarization and Activation polarization
d) Neither concentration nor Activation polarization

Answer: b
Clarification: Activation polarization is the mechanism of polarization in which the activation energy of reactants at the interface is the driving force. It has a negligible effect on velocity as it is independent of diffusion of ions in the bulk solution.

5. Severe corrosion of metals occurred when coupled with platinum is due to the higher current density for hydrogen evolution but not due to the reversible potential of the platinum-platinum ion electrode.
a) True
b) False

Answer: a
Clarification: Severe corrosion of metals occurred when coupled with platinum is due to the higher current density for evolution but not due to the reversible potential of the platinum-platinum ion electrode. Notably, platinized platinum has the highest exchange current density for hydrogen evolution.

6. The reversible potential of gold is more positive than platinum in emf series whereas in galvanic series the position of gold is below platinum.
a) False
b) True

Answer: b
Clarification: The reversible potential of gold is more positive than platinum in emf series whereas in galvanic series the position of gold is below platinum. It is due to the exchange current density of hydrogen evolution, as the galvanic tests are usually conducted in an acidic environment.

7. In a galvanic couple, the corrosion rate of the metal with active corrosion potential is accelerated whereas the corrosion rate of noble metal retards preferentially.
a) True
b) False

Answer: a
Clarification: In a galvanic couple, one metal acts as the anode (active corrosion potential), and its corrosion rate is accelerated whereas other acts as the cathode (noble metal) and its corrosion rate are retards preferentially.

8. Which of the following metals that are spontaneously passivated on coupling with platinum?
a) Titanium
b) Chromium
c) Titanium and Chromium
d) Neither titanium nor chromium

Answer: c
Clarification: Titanium and chromium metals are the metals that are spontaneously passivated on coupling with platinum. It is due to the mixed potential of galvanic couples lies in the protection region of the passive region.

9. Which of the following is/are correct regarding the potentiostat method?
a) It is a polarization technique that allows for controlled polarization
b) It works on controlling voltage between a working and reference electrode
c) It is a corrosion analysis method
d) It is a corrosion analysis technique method that allows for controlled polarization and it works on controlling voltage between a working and reference electrode.

Answer: d
Clarification: It is a corrosion analysis technique method that allows for controlled polarization and it works in controlling voltage between a working and reference electrode.