20 + Interview Questions in Modern Theory Applications in Corrosion Engineering Page 1 InterviewSolution

1.	Which of the following is/are the advantages of Tafel extrapolation?(a) It can measure extremely low corrosion rates(b) It can be used for continuously monitoring the corrosion rate of a system(c) It can be used for continuously monitoring the corrosion rate of a system with high accuracy and measures extremely low corrosion rates(d) It can be performed rapidly with high accuracyThis question was posed to me during an interview for a job.I need to ask this question from Modern Theory Applications in section Modern Theory Applications of Corrosion Engineering
Answer» CORRECT choice is (c) It can be used for continuously monitoring the corrosion rate of a system with high accuracy and measures EXTREMELY low corrosion rates The EXPLANATION is: Advantages of Tafel EXTRAPOLATION are: It can measure extremely low corrosion rates It can be used for continuously monitoring the corrosion rate of a system It can be performed rapidly with high accuracy.

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2.	The corrosion rate is usually dependent at low velocity whereas at high velocities it becomes independent.(a) True(b) FalseThe question was posed to me in final exam.I need to ask this question from Modern Theory Applications in chapter Modern Theory Applications of Corrosion Engineering
Answer» The correct ANSWER is (a) True Best 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.

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3.	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) FalseI have been asked this question in an international level competition.Enquiry is from Modern Theory Applications topic in chapter Modern Theory Applications of Corrosion Engineering
Answer» Correct answer is (a) True To ELABORATE: 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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4.	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 layerI had been asked this question in an online interview.My question comes from Modern Theory Applications topic in division Modern Theory Applications of Corrosion Engineering
Answer» CORRECT option is (B) Rate of corrosion increases with increase in oxidizers concentration To elaborate: 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.

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5.	Which of the following is/are the limitations of Tafel extrapolation?(a) For reasonable accuracy, the Tafel region must be extended(b) It can be applied to systems containing one reduction process only(c) Much interference from concentration polarization(d) It can be applied to systems containing one reduction process, for reasonable accuracy the Tafel region must be extended and there will be much interference from concentration polarizationThis question was addressed to me in my homework.Query is from Modern Theory Applications topic in division Modern Theory Applications of Corrosion Engineering
Answer» Correct choice is (d) It can be APPLIED to SYSTEMS CONTAINING one reduction process, for reasonable accuracy the Tafel region must be extended and there will be much interference from concentration POLARIZATION Easy explanation: Limitations of Tafel extrapolation are: For reasonable accuracy, the Tafel region must be extended It can be applied to systems containing one reduction process only Much interference from concentration polarization.

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6.	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.I had been asked this question in a national level competition.My enquiry is from Modern Theory Applications topic in division Modern Theory Applications of Corrosion Engineering
Answer» The correct answer is (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. 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.

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7.	Which of the following industries uses Tafel extrapolation or linear polarization to measure low corrosion rates?(a) Nuclear industries(b) Pharmaceutical industries(c) Food processing industries(d) Nuclear, pharmaceutical and food processing industriesThe question was asked in a job interview.This interesting question is from Modern Theory Applications topic in division Modern Theory Applications of Corrosion Engineering
Answer» CORRECT choice is (d) Nuclear, pharmaceutical and food processing industries The explanation: Nuclear, pharmaceutical, and food processing industries are the industries that USE Tafel extrapolation or linear POLARIZATION where measuring LOW CORROSION rates is important. Traces of impurities or contamination in these industries could lead to catastrophic failure.

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8.	Which of the following noble metals will improve the corrosion resistance of titanium and chromium on galvanic coupling?(a) Platinum(b) Palladium(c) Rhodium(d) Platinum, palladium, and rhodiumThe question was posed to me in final exam.The above asked question is from Modern Theory Applications topic in portion Modern Theory Applications of Corrosion Engineering
Answer» The correct OPTION is (d) Platinum, palladium, and RHODIUM Explanation: Noble metals such as platinum, palladium, and rhodium on galvanic coupling will IMPROVE the corrosion resistance of titanium and chromium by spontaneous PASSIVATION. It is due to the mixed potential of the couple lies in the passive region of titanium and chromium.

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9.	The applied current cathodic polarization curve of a corroding metal is non-linear at low currents, but it becomes linear at higher currents on a semilogarithmic plot.(a) False(b) TrueI have been asked this question in examination.The query is from Modern Theory Applications topic in chapter Modern Theory Applications of Corrosion Engineering
Answer» The CORRECT answer is (b) True The EXPLANATION is: The CATHODIC polarization curve is the curve drawn by measuring over voltage between reference and the working electrode on a semilogarithmic plot. It is non-linear at LOW CURRENTS whereas it becomes linear at higher currents.

Discussion

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) TrueThis question was posed to me in an interview for internship.Enquiry is from Modern Theory Applications in portion Modern Theory Applications of Corrosion Engineering
Answer» CORRECT answer is (B) True The 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.

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11.	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 measurementI had been asked this question during an interview for a job.This intriguing question originated from Modern Theory Applications in portion Modern Theory Applications of Corrosion Engineering
Answer» Correct answer is (d) Permit PREDICTION of COMPLEX corrosion behavior, to develop NEW corrosion prevention methods and to develop new RAPID corrosion rate MEASUREMENT Best 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.

Discussion

12.	What is the formula to determine the slope of linear polarization curve?(a) ΔE/Δi =[2.3icorr(βa+βb)]/[βaβb](b) ΔE/Δi=[βa+βb]/[2.3icorr(βaβb)](c) ΔE/Δi=[βaβb]/[2.3icorr(βa+βb)](d) ΔE/Δi=[2.3icorr(βaβb)]/[βa+βb]I had been asked this question in an interview for internship.The above asked question is from Modern Theory Applications in portion Modern Theory Applications of Corrosion Engineering
Answer» The CORRECT choice is (c) ΔE/Δi=[βaβb]/[2.3icorr(βa+βb)] To elaborate: The slope of linear polarization curve is determined by using ΔE/Δi=[βaβb]/[2.3icorr(βa+βb)] where βa , βb are TAFEL slopes of ANODIC and CATHODIC reactions and icorr is the current density at the INTERSECTION point of anodic and cathodic reaction.

Discussion

13.	Which of the following electrochemical methods is/are used to determine the corrosion rate?(a) Tafel extrapolation(b) Linear polarization(c) Tafel extrapolation and linear polarization(d) Neither Tafel extrapolation nor linear polarizationI got this question in a national level competition.My question is based upon Modern Theory Applications topic in division Modern Theory Applications of Corrosion Engineering
Answer» The CORRECT ANSWER is (c) TAFEL extrapolation and linear polarization The explanation is: Tafel extrapolation and linear polarization are the two electrochemical METHODS used to DETERMINE the corrosion rate. These methods are extensively used for laboratory and industrial corrosion tests.

Discussion

14.	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 polarizationThe question was asked at a job interview.This intriguing question comes from Modern Theory Applications in division Modern Theory Applications of Corrosion Engineering
Answer» Right choice is (b) Activation POLARIZATION 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.

Discussion

15.	Stainless steels containing small quantities of platinum passivates more readily in the presence of oxygen, ferric salts, and other oxidizing agents.(a) False(b) TrueThe question was posed to me in an interview for job.This key question is from Modern Theory Applications topic in chapter Modern Theory Applications of Corrosion Engineering
Answer» The correct ANSWER is (b) True The best explanation: STAINLESS steels containing SMALL quantities of platinum passivates more readily in the presence of oxygen, FERRIC SALTS, and other oxidizing agents. It is due to the resultant mixed potential of an alloy that reaches a passive region quickly.

Discussion

16.	What is the range of current density around corrosion potential that will observe that the applied current density is a linear function of the electrode potential?(a) 10 mV more noble or active around corrosion potential(b) 5 mV more noble or active around corrosion potential(c) 10 V more noble or active around corrosion potential(d) 5 V more noble or active around corrosion potentialThe question was posed to me in an online quiz.The origin of the question is Modern Theory Applications topic in division Modern Theory Applications of Corrosion Engineering
Answer» RIGHT option is (a) 10 mV more noble or ACTIVE around corrosion POTENTIAL Easiest explanation: In around 10 millivolts around corrosion potential, it is observed that the applied current density is a linear FUNCTION of the electrode potential. It is known as a linear polarization curve.

Discussion

17.	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) FalseThe question was asked during an internship interview.Asked question is from Modern Theory Applications topic in section Modern Theory Applications of Corrosion Engineering
Answer» Correct answer is (a) True The best I can explain: 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.

Discussion

18.	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 chromiumI got this question in my homework.The question is from Modern Theory Applications topic in division Modern Theory Applications of Corrosion Engineering
Answer» Correct choice is (c) Titanium and Chromium The 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.

Discussion

19.	The optimum potential for anodic protection is in the mid of passive region since it permits slight variations.(a) True(b) FalseThis question was posed to me in an interview.The origin of the question is Modern Theory Applications topic in section Modern Theory Applications of Corrosion Engineering
Answer» The correct ANSWER is (a) True The best explanation: Anodic protection is a corrosion prevention method in which anodic current of certain potential is provided to the metallic structure to transform from active to a passive STATE. The OPTIMUM potential for anodic protection is in the mid of passive region SINCE it permits slight variations.

Discussion

20.	What is meant by anodic protection?(a) Accompanying the sacrificial metal with metallic structure(b) Prevention of corrosion by impressed cathodic current by supply electrons(c) Prevention of corrosion by the impressed anodic current is used to transform from active to a passive state(d) Additions of oxidizers and oxidizing agents for the formation of an oxide layerThe question was posed to me by my college professor while I was bunking the class.My doubt stems from Modern Theory Applications in chapter Modern Theory Applications of Corrosion Engineering
Answer» Right answer is (c) PREVENTION of corrosion by the impressed anodic current is used to transform from ACTIVE to a passive state For explanation I would say: Anodic PROTECTION is ONE of the corrosion prevention or protection method in which the impressed anodic current is used to transform from active to a passive state.

Discussion

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The corrosion rate is usually dependent at low velocity whereas at high velocities it becomes independent.(a) True(b) FalseThe question was posed to me in final exam.I need to ask this question from Modern Theory Applications in chapter Modern Theory Applications of Corrosion Engineering

The optimum potential for anodic protection is in the mid of passive region since it permits slight variations.(a) True(b) FalseThis question was posed to me in an interview.The origin of the question is Modern Theory Applications topic in section Modern Theory Applications of Corrosion Engineering