Corrosion - Physical Metallurgy - Metallurgical Engineering Previous Year Questions

1

2007 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2007

Identify the incorrect statement.

A

A concentration gradient in the electrolyte may lead to the formation of a galvanic cell

B

Chromium is added to improve the oxidation resistance of stainless steels

C

Cathodic protection can be provided by applying a coating

D

A steel bolt or nut is permissible on a large copper vessel

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2

2008 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2008

Intergranular corrosion of 18-8 stainless steel can NOT be prevented by

A

reducing the carbon content to less than 0.05%

B

quenching it from high temperature to prevent chromium carbide precipitation

C

adding strong carbide forming elements

D

increasing the carbon content

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3

2008 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2008

The Pilling-Bedworth ratio for the oxidation of Al is

A

0.57

B

0.74

C

1.38

D

3.12

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4

2008 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2008

The oxidation law that governs the high temperature oxidation of Al is

A

parabolic

B

linear

C

logarithmic

D

paralinear

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5

2009 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2009

From the list given below:
P.   Cu
Q.   Mg
R.   Ni
S.   Zn
Two metals which provide cathodic protection to steel are

A

P, R

B

R, S

C

Q, R

D

Q, S

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6

2011 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2011

Zinc rod is immersed in dilute HCl (pure). If a very small amount of FeCl3 is added to the solution, the corrosion rate of zinc

A

decreases

B

increases

C

remains constant

D

is zero (passivation)

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7

2012 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2012

When a zinc metal rod is immersed in dilute hydrochloric acid, it results in

A

Evolution of hydrogen

B

Evolution of chlorine

C

Evolution of oxygen

D

No evolution of any gas

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8

2012 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2012

Match the principles given in Group I with corresponding corrosion terminology in Group II

A

P-3, Q-4, R-1, S-2

B

P-3, Q-4, R-2, S-1

C

P-4, Q-2, R-1, S-3

D

P-2, Q-1, R-4, S-3

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9

2012 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2012

Identify the correct combination of the following statements
P. Hydrogen electrode is a standard used to measure redox potentials
Q. Activation polarization refers to electrochemical processes controlled by reaction sequence at metal-solution interface
R. Potential-pH diagrams can be used to predict corrosion rates of metals
S. Cathodic protection can use sacrificial anodes such as magnesium

A

P, Q and R

B

Q, R and S

C

P, Q and S

D

P, R and S

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10

2013 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2013

Which one of the following can give information about the corrosion rate?

A

Pourbaix diagram

B

Polarization technique

C

EMF series

D

Galvanic series

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11

2014 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2014

The Pilling-Bedworth ratio is defined as

A

The molar weight of an oxide divided by the molar weight of the metal consumed in oxide formation.

B

The volume of the oxide divided by the volume of the metal consumed in oxide formation.

C

The density of the oxide divided by the density of the metal consumed in oxide formation.

D

The molar Gibbs energy of the oxide divided by the Gibbs energy of the metal consumed in oxide formation.

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12

2014 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2014

Which one of the following can avoid weld decay of austenitic stainless steels?

A

Reducing carbon content

B

Increasing carbon content

C

Eliminating strong carbide formers

D

Decreasing chromium content

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13

2014 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2014

Match the types of corrosion in Group I with their examples in Group II.

Group I	Group II
P. Galvanic corrosion Q. Filiform corrosion R. Stress corrosion cracking S. Crevice corrosion	1. Season cracking in brass 2. Nut-bolt assembly with gasket 3. Brass fittings joined with lead-tin solder 4. Painted food can

A

P-4, Q-1, R-2, S-3

B

P-3, Q-1, R-4, S-2

C

P-3, Q-4, R-1, S-2

D

P-4, Q-2, R-3, S-1

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14

2016 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2016

The passive film in stainless steel forms above the

A

Primary passive potential

B

Breakdown potential

C

Trans-passive potential

D

Pitting potential

Check answer

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15

2018 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2018

Which of the following materials are protected by passivation (i.e., formation of a thin adherent film on the surface) from corrosion?
P. Aluminium alloys
Q. Mild steel
R. Stainless steel
S. Silver

A

P & Q

B

Q & R

C

Q & S

D

P & R

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16

2019 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2019

The carbide that is primarily responsible for intergranular corrosion in austenitic stainless steel is ____________.

A

\(Cr_{23}C_6\)

B

\(Fe_3C\)

C

\(SiC\)

D

\(Mn_3C\)

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17

2020 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2020

Which one of the following statements regarding selective leaching of a binary alloy is TRUE?

A

The lower atomic weight element is leached.

B

The element having higher diffusivity is leached.

C

The more electronegative element is leached.

D

The element with lower density is leached.

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18

2020 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2020

An iron plate with a total exposed surface area of 50 cm² undergoes atmospheric corrosion. If 200 g of weight is lost over a period of 10 years, then the corrosion rate is ______ kg.m⁻².year⁻¹ (round off to the nearest integer).

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19

2023 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2023

Choose the correct statement(s) in the context of fusion welding of austenitic stainless steel containing about 0.06 wt.% carbon.

A

Corrosion resistance of heat affected zone is poorer than base material.

B

Corrosion resistance of heat affected zone is superior than fusion zone.

C

Corrosion resistance of heat affected zone is same as fusion zone.

D

Corrosion resistance is same for fusion zone, heat affected zone, and base material.

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20

2024 · Metallurgical Engineering · Physical Metallurgy · Corrosion

Metallurgical Engineering (MT) 2024

The microstructures of a quenched steel tempered at three temperatures \(T_1 < T_2 < T_3\) for a fixed time are schematically illustrated. The solid circles represent cementite particles in ferrite matrix; \(\bar{r}_1\), \(\bar{r}_2\) and \(\bar{r}_3\) are average radii of cementite particles, and \(V_1\), \(V_2\) and \(V_3\) are volume fractions of cementite at temperatures \(T_1\), \(T_2\) and \(T_3\), respectively.
If the cementite in steel is more noble than ferrite, then which one of the three microstructures will have the highest corrosion rate when exposed to an aqueous solution of 3.5 wt. % NaCl?

A

Microstructure at \(T_1\)

B

Microstructure at \(T_2\)

C

Microstructure at \(T_3\)

D

Independent of microstructure

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