Subject: Corrosion Engineering
Course Instructor: Dr. Ameeq Farooq
INSTITUTE OF METALLURGY & MATERIALS ENGINEERING
UNIVERSITY OF THE PUNJAB, LAHORE
Practice Questions: Set-01
Semester: 6th
Date: 08-05-2023
Note: Before starting to solve the practice questions read out the following articles from your
lecture notes and text book*
Faraday’s Law of Electrolysis and Corrosion rate Expression
(Faraday’s constant =96,487C/mole)
PQ# 1: 15 g of aluminum metal are dissolved in a 1 M HCl solution. How many charges in
coulombs have been produced by the anodic process?
( Al  Al 3  3e ; Molar mass of aluminum (Al) = 26.98 g/mole)
(Answer: Q=160930.8747C)
PQ # 2: A sheet of zinc one meter wide by three-meter long has lost 40 g to corrosion over the
past 80 days. Estimate weight loss in gmd.
( Zn  Zn 2  2e  ; Molar mass of zinc (Zn) = 65.38 g/mole; grams per square meter per day
(gmd))
(Answer: Weight loss = 0.166gmd)
PQ # 3: 23 g weight of copper (2 m × 1 m) loss in 15 years. Estimate that penetration rate in
mm/year.
(Millimeters per year (mm/year); Cu  Cu 2  2e ; Density of copper = ρ= 8.96g/cm3; Molar
mass of copper (Cu)= 63.55 g/mole)
(Answer: Penetration rate=8.56×106 mm/year)
PQ # 4: What would be the total corrosion current density associated with copper corrosion rate
0.04 gmd?
(Molar mass of copper (Cu) = 63.55 g/mole; Cu  Cu 2  2e )
(Answer: i=1.40 mA/m2 )
PQ # 5: Find the charge in coulomb which dissolute 12 g of silver in silver nitrate solution?
( Ag  Ag 1  e ; Molar mass of silver (Ag) = 107.9 g/mole; Density of silver = ρ =10.5g/cm3)
(Answer: Q=10730.7136 C)
PQ # 6: How long has a current of 3 A to be applied through a solution of silver nitrate to
dissolve a metal surface of 80 g?
( Ag  Ag 1  e ; Molar mass of silver (Ag) = 107.9 g/mole; Density of silver = ρ =10.5g/cm3)
(Answer: t=23846.03028 s)
PQ # 7: Copper dissolved 9.85 g in 5 hours through acid solution. Calculate the magnitude of the
current in ampere.
(Molar mass of copper (Cu) = 63.55 g/mole; Cu  Cu 2  2e )
(Answer: I=1.66 A)
PQ # 8: Derive the general relation between gmd and mdd.
(grams per square meter per day (gmd); milligram per square decimeter per day (mdd))
(Answer: 1gmd=10mdd)
PQ # 9: Magnesium corrodes in seawater at a rate of 1.45 gmd. Estimate the rate in mm/y?
(Density of magnesium = ρ =1.74g/cm3; grams per square meter per day (gmd); millimeters per
year (mm/y))
(Answer: Penetration rate=0.3041 mm/year)
PQ # 10: Lead corrodes in seawater at a rate of 1.45 gmd. Estimate the rate in mils/y (mpy)?
(Density of Lead = ρ= 11.35g/cm3; grams per square meter per day (gmd); mils per year (mpy))
(Answer: Penetration rate=1.835 mpy)
Page 1 of 2
Subject: Corrosion Engineering
Course Instructor: Dr. Ameeq Farooq
PQ # 11: Aluminum corrodes in tap water at a rate of 1.5 gmd. Estimate the rate in in/year (ipy)?
(Direction: Density of aluminum = ρ =2.70 g/cm3; grams per square meter per day (gmd); inch
per year (ipy))
(Answer: Penetration rate=7.98×103 ipy)
PQ # 12: Laboratory corrosion tests on three alloys in an industrial waste solution show the
following results:
Density of Material (ρ)
Material
Weight Loss
Pitting Factor
(g/cm3 )
(gmd)
A
2.7
40
1
B
9.0
62
2
C
7.8
5.6
9.2
Estimate maximum penetration in millimeters for each material at the end of one year.
Weight loss
Maximum Penetration
( Penetration rate 
; Pitting factor 
)
Penetration rate

(Answer: (A) Maximum Penetration =5.40 mm/year, (B) Maximum Penetration =5.028 mm/year, (C)
Maximum Penetration =2.41 mm/year)
PQ # 13: Derive the general relation between mm/y and gmd.
(Direction: grams per square meter per day (gmd); millimeters per year (mm/y))
(Answer: 1gmd=0.365ρ mm/year)
PQ # 14: Iron corrodes in an aqueous solution; the corrosion current is measured as 0.1 A/cm2.
Estimate the rate of weight loss per unit area in units of mdd.
(milligram per square decimeter per day (mdd); Molar mass of iron (Fe) = 55.84 g/mole;
Fe  Fe2  2e )
(Answer: weight loss=250034.0979 mdd)
PQ # 15: Derive the general relation between gmd and mpy.
(grams per square meter per day (gmd); mils per year (mpy))
(Answer: 1gmd=14.37ρ mpy)
* Reference Book:
1. I. H. Khan; “Corrosion Technology”, Vol.1, Ed.2, AFAQ Publisher, Lahore, Pakistan;
p.5-6, 41-44.
2. R. Winston Revie, Herbert H. Uhlig “Corrosion and Corrosion Control: An
Introduction to Corrosion Science and Engineering” Ed.4, John Wiley & Sons, Inc.,
Hoboken New Jersey; p.9-10, 16-17, 19.
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