Corrosion Engineering Questions and Answers – Corrosion Principles – Electrochemical Aspects – 2

«
»

This set of Corrosion Engineering Questions and Answers for Freshers focuses on “Corrosion Principles – Electrochemical Aspects – 2”.

1. Concentration polarization is considered in both anodic and cathodic reactions.
a) True
b) False
View Answer

Answer: b
Explanation: Concentration polarization refers to the electrochemical reaction that is controlled by the diffusion of ions in an electrolyte. This occurs in the low concentration of electrolyte. It is neglected in the case of anodic reaction (metal dissolution) because there is a sufficient supply of metal atoms in a metallic piece and there is no need for diffusion.
advertisement

2. Which of the following polarization will be influenced by electrolytic agitation?
a) Activation polarization
b) Resistance polarization
c) Concentration polarization
d) Both Activation and Resistance polarization
View Answer

Answer: c
Explanation: Concentration polarization refers to the electrochemical reaction that is controlled by the diffusion of ions in an electrolyte. With an increase in the velocity or agitation of the electrolyte the contact of ions with metal interface increases.

3. What is meant by passivation?
a) Loss of reactivity
b) Increase in reactivity
c) Increase in corrosion rate
d) Deterioration of metal
View Answer

Answer: a
Explanation: Passivation is the state of metal in which stable films or barriers are formed. These stable films obstruct the contact of corrosive medium to the metal surface. Most of the engineering metals undergo passivation under different atmospheric conditions.
Note: Join free Sanfoundry classes at Telegram or Youtube
advertisement
advertisement

4. Which of the following metal is depicted in the given graph?
Metal depicted in graph is active metal increases with increase in oxidizing potential
a) Active metal
b) Passive metal
c) Active-Passive metal
d) Trans passive state of metal
View Answer

Answer: a
Explanation: The corrosion rate of active metal increases with an increase in the oxidizing potential of the environment. In the case of passive metal, it remains almost constant at a lower corrosion rate value. Whereas in the case of trans passive state of metal the corrosion increases from a certain value due to the damage of protective film.

5. Which of the following metal is depicted is in the given figure?
Metal depicted in graph is active-passive transition metal undergoing transition
a) Active metal
b) Passive metal
c) Active-Passive transition metal
d) Trans passive state of metal
View Answer

Answer: c
Explanation: Active-Passive transition metal is a metal that undergoes a transition from active to passive state after a certain oxidation potential. The oxidation potential from which the passivation starts is called critical oxidation potential. Fortunately, most of the engineering metals are active-passive metals that protect from corrosion.
advertisement

6. What is the trans passive region?
a) Region after passive state
b) Formed by breakage of the protective film in the passive region
c) Constant corrosion rate
d) Region formed after passive state by breakage of the passive oxide layer
View Answer

Answer: d
Explanation: Trans passive region is formed in an active-passive transition metal after crossing the limiting oxidizing potential after a passive region. This occurs due to the breakage of the protective layer due to the unbearable oxidizing potential of the corrosive medium.

7. Which of the following is denoted as // in an electrochemical cell notation?
a) Anode
b) Cathode
c) Electrolyte
d) Salt bridge
View Answer

Answer: d
Explanation: Salt bridge is a connection between two half cells used to neutralize the ions with respective opposite charged ions. Usually, strong electrolytes such as KCl along with agar-agar gel are used.
advertisement

8. Which of the following gives Standard cell potential of a cell (Eo)?
a) Eocathode-Eoanode
b) Eoanode-Eocathode
c) Eocathode*Eoanode
d) Eoanode/Eocathode
View Answer

Answer: a
Explanation: A electrochemical cell consist of two electrodes with a potential difference preferentially one acts as a cathode and other as an anode. The standard state of each specific electrode is constant and it measured against the hydrogen electrode at 25°C and 1 atm pressure. And standard cell potential is calculated as Eocathode-Eoanode.

9. Which of the following is a Nernst equation?
a) Ecell=Eocell–RT/nF ln(K)
b) Ecell=Eocell–nF/RT ln(K)
c) E0cell=Ecell–RT/nF ln(K)
d) E0cell=Ecell–nF/RT ln(K)
View Answer

Answer: a
Explanation: Ecell=Eocell–RT/nF ln(K) is the Nernst equation. Eocell is the potential of a cell in the standard state, R is Universal gas constant, n is the valency of ion, T is absolute temperature, F is Faraday’s constant and K is the reaction quotient, Ecell is the cell potential.
advertisement

10. Zn/Zn+2(0.1M)//Ag+1(1M)/Ag is the cell notation of zinc dissolution in silver. Then what is the Electrode potential of the cell formed? (T=298K, F=96500, R=8.314 J/Kg*K)
a) 1.57
b) 2.57
c) 1.25
d) 2.75
View Answer

Answer: a
Explanation: Chemical reaction can be written as Zn + 2Ag+1==>Zn+2+2Ag
Eocell=0.80-(-0.763) (since Eosilver=0.80V, Eozinc=-0.763V)
Eocell=1.563V
Ecell=Eocell–RT/nF ln(K)
Ecell=1.563-[(8.314*298)/2*96500)]ln([products]/[reactants])
Ecell=1.563-[(8.314*298)/2*96500)]ln(0.1/1)
Ecell=1.563-[(8.314*298)/2*96500)]ln(0.1)
Ecell=1.563+0.01283
Ecell=1.57583 V.

Sanfoundry Global Education & Learning Series – Corrosion Engineering.
To practice all areas of Corrosion Engineering for Freshers, here is complete set of 1000+ Multiple Choice Questions and Answers.

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
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.

Subscribe to his free Masterclasses at Youtube & technical discussions at Telegram SanfoundryClasses.