Corrosion Engineering Questions and Answers – Modern Theory Applications – Predicting Corrosion Behavior

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This set of Corrosion Engineering Questions and Answers for Aptitude test focuses 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
View Answer

Answer: d
Explanation: 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.
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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
View Answer

Answer: b
Explanation: 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. Which of the following is described in the given figure?
The figure describes effect of oxidizers concentration on electrochemical behavior
a) Effect of oxidizers concentration on cathodic behavior of active metal
b) Effect of oxidizers concentration on the electrochemical behavior of active metal
c) Effect of oxidizers concentration on the electrochemical behavior of active-passive transition metal
d) Effect of oxidizers concentration on cathodic behavior of active-passive transition metal
View Answer

Answer: c
Explanation: The given figure describes the effect of oxidizers concentration on the electrochemical behavior of active-passive transition metal. The rate of oxygen reduction (cathodic reaction) varies with oxidizer concentration and the corresponding rate of metallic dissolution (anodic reaction) varies.
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4. What is the potential of oxidizers at which metal passivation starts according to a given figure?
Potential of oxidizer at which metal passivation start in concentration corresponding to C
a) Concentration corresponding to C
b) Concentration corresponding to D
c) Concentration corresponding to A
d) Concentration corresponding to B
View Answer

Answer: a
Explanation: Given the figure describes the effect of oxidizer concentration (potential) on the electrochemical behavior of active-passive transition metal. Passivation of metal starts at the oxidizer’s concentration corresponding to point C.

5. Which of the following is described in the given figure?
The figure depicts effect of velocity on the electrochemical behavior of a normal metal
a) Effect of velocity on anodic dissolution of oxygen
b) Effect of velocity on the electrochemical behavior of active-passive transition metal
c) Effect of velocity on the electrochemical behavior of a normal metal
d) Effect of velocity on the cathodic dissolution of metal
View Answer

Answer: c
Explanation: The given figure depicts the effect of velocity on the electrochemical behavior of a normal metal. Here metallic dissolution is anodic reaction and reduction of oxygen is a cathodic reaction.
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6. The corrosion rate is usually dependent at low velocity whereas at high velocities it becomes independent.
a) True
b) False
View Answer

Answer: a
Explanation: 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.

7. 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
View Answer

Answer: b
Explanation: 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.
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8. Which of the following is depicted in the given figure?
The figure depicts the galvanic effect of zinc-platinum increase in corrosion of zinc
a) Galvanic effect of copper-platinum
b) Corrosion of platinum
c) Corrosion of Zinc
d) Galvanic effect of zinc-platinum
View Answer

Answer: d
Explanation: The given figure depicts the galvanic effect of zinc-platinum. Corrosion of zinc increases (anodic reaction) preferentially as the total rate of hydrogen evolution (cathodic reaction) increases on zinc and platinum.

9. 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
View Answer

Answer: a
Explanation: 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.
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10. 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
View Answer

Answer: b
Explanation: 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.

11. Which of the following is depicted in the given figure?
The figure depicts the effect of the cathode-anode area ratio of the zinc-platinum couple
a) Galvanic effect of the zinc-platinum couple
b) Effect of the velocity of zinc-platinum couple
c) Effect of the cathode-anode area ratio of a zinc-platinum couple
d) Effect of oxidizers on the zinc-platinum couple
View Answer

Answer: c
Explanation: The given figure depicts the effect of the cathode-anode area ratio of the zinc-platinum couple. The exchange current density of hydrogen evolution on platinum (10cm2) is more than the current density of platinum (1cm2).

12. 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
View Answer

Answer: a
Explanation: 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.

13. 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
View Answer

Answer: c
Explanation: 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.

14. 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.
View Answer

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

Sanfoundry Global Education & Learning Series – Corrosion Engineering.

To practice all areas of Corrosion Engineering for Aptitude test, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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