Metal Corrosion and Prevention - Degradation of Materials - Engineering Sciences Previous Year Questions

1

2007 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2007

According to Galvanic series, the most active metal among the following is

A

Mg

B

Zn

C

Sn

D

Al

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2

2008 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2008

Which one of the following may NOT help in resisting the weld decay or intergranular corrosion in austenitic stainless steel?

A

Heating the stainless steel to 1000°C followed by quenching to room temperature

B

Heating the stainless steel to 1000°C followed by furnace cooling

C

Lowering the carbon content to 0.03 wt. % in the stainless steel

D

Alloying the stainless steel with Nb or Ti

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3

2009 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2009

Inter-granular corrosion of austenitic stainless steel is promoted by

A

Fine grained microstructure

B

Coarse grained microstructure

C

Soaking steel at 700 °C in air

D

Quenching from 1000 °C

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4

2011 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2011

The oxide scale responsible for the excellent corrosion resistance of stainless steels is

A

Cr₂O₃

B

NiO

C

Fe₂O₃

D

Al₂O₃

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5

2012 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2012

The Pilling-Bedworth ratio is defined as the ratio of

A

Volume of oxide to volume of metal

B

Weight of oxide to weight of metal

C

Density of oxide to density of metal

D

Surface area of oxide to surface area of metal

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6

2013 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2013

Which one of the following metals is commonly alloyed with iron to improve its corrosion resistance?

A

Co

B

Cr

C

Ti

D

Nb

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7

2015 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2015

A 1 kg sacrificial anode of Mg (atomic weight: 24.31 amu) is attached to the base of a ship. If the anode lasts for 60 days, what is the average corrosion current (in Amperes) during that period?

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8

2019 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2019

Pilling-Bedworth ratios for oxides of some metals are given in the table.

Metal	Pilling-Bedworth Ratio
Li	0.57
Ce	1.16
Ta	2.33
W	3.40

Based on the criterion of Pilling-Bedworth ratio alone, which one of the following metals will be most protected from high temperature oxidation?

A

Li

B

Ce

C

Ta

D

W

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9

2019 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2019

Nickel corrodes at 298 K in a solution of 0.06 M nickel chloride having pH 4. Assuming complete dissociation of nickel chloride, the partial pressure of hydrogen required to stop the corrosion of nickel is ____ atm. (round off to the nearest integer) (Given: Standard reduction potential of nickel = -0.25 V, Faraday's constant = 96500 C mol⁻¹, Universal gas constant = 8.314 J K⁻¹ mol⁻¹)

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10

2020 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2020

Isothermal weight gain per unit area (ΔW/A, where ΔW is the weight gain (in mg) and A is the area (in cm²)) during oxidation of a metal at 600 °C follows parabolic rate law, where, ΔW/A = 1.0 mg.cm⁻² after 100 min of oxidation. The ΔW/A after 500 min at 600 °C will be ______ mg.cm⁻² (round-off to two decimal places).

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11

2021 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2021

When a metal (M) is immersed in de-aerated acid electrolyte, it polarizes anodically by 0.4 V. The M/Mⁿ⁺ exchange current density is \(10^{-5} \; \mathrm{A \; m^{-2}}\) and Tafel slope is 0.1 V/decade for the anodic reaction. Assume that corrosion is uniform, and anodic and cathodic reactions are under activation control. The rate of metal dissolution in \(\mathrm{A \; m^{-2}}\) is __________ (round off to 1 decimal place)

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12

2024 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2024

Which of the following is/are responsible for pitting corrosion in a metal ?

A

Rough surface

B

Grain boundaries

C

Polished surface

D

Polymer coated metal surface

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13

2025 · Engineering Sciences · Degradation of Materials · Metal Corrosion and Prevention

Engineering Sciences (XE) 2025

Corrosion of pure iron takes place in an acidic electrolyte by forming Fe^{2+} ions at ambient condition. The corrosion current density is measured to be 2 × 10^{-4} A cm^{-2}. The corrosion rate (in mm per year) of iron is (rounded off to one decimal place) ______

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