Callister - An introduction - 8th edition

718 • Chapter 17 / Corrosion and Degradation of Materials
17.29 According to Table 17.3, the oxide coating
that forms on silver should be nonprotective,
and yet Ag does not oxidize appreciably at
room temperature and in air. How do you
explain this apparent discrepancy?
17.30 In the following table, weight gain–time data
for the oxidation of copper at an elevated
temperature are given.
W (mg/cm 2 ) Time (min)
0.316 15
0.524 50
0.725 100
(a) Determine whether the oxidation kinetics
obey a linear, parabolic, or logarithmic
rate expression.
(b) Now compute W after a time of
450 min.
17.31 In the following table, weight gain–time data
for the oxidation of some metal at an elevated
temperature are given.
W (mg/cm 2 ) Time (min)
4.66 20
11.7 50
41.1 135
(a) Determine whether the oxidation kinetics
obey a linear, parabolic, or logarithmic
rate expression.
(b) Now compute W after a time of 1000 min.
DESIGN PROBLEMS
17.D1 A brine solution is used as a cooling
medium in a steel heat exchanger. The
brine is circulated within the heat exchanger
and contains some dissolved oxygen.
Suggest three methods, other than
cathodic protection, for reducing corrosion
of the steel by the brine. Explain the rationale
for each suggestion.
17.D2 Suggest an appropriate material for each of
the following applications, and, if necessary,
recommend corrosion prevention measures
that should be taken.Justify your suggestions.
(a) Laboratory bottles to contain relatively
dilute solutions of nitric acid
(b) Barrels to contain benzene
17.32 In the following table, weight gain–time data
for the oxidation of some metal at an elevated
temperature are given.
W (mg/cm 2 ) Time (min)
1.90 25
3.76 75
6.40 250
(a) Determine whether the oxidation kinetics
obey a linear, parabolic, or logarithmic
rate expression.
(b) Now compute W after a time of 3500
min.
Spreadsheet Problems
17.1SS Generate a spreadsheet that will determine
the rate of oxidation (in mol/cm # 2 s) and the
corrosion potential for a metal that is immersed
in an acid solution. The user is allowed
to input the following parameters
for each of the two half-cells: the corrosion
potential, the exchange current density, and
the value of .
17.2SS For the oxidation of some metal, given a set
of values of weight gain and their corresponding
times (at least three values), generate
a spreadsheet that will allow the user
to determine the following: (a) whether the
oxidation kinetics obey a linear, parabolic, or
logarithmic rate expression, (b) values of the
constants in the appropriate rate expression,
and (c) the weight gain after some other time.
(c) Pipe to transport hot alkaline (basic) solutions
(d) Underground tanks to store large quantities
of high-purity water
(e) Architectural trim for high-rise buildings
17.D3 Each student (or group of students) is to
find a real-life corrosion problem that has
not been solved, conduct a thorough investigation
as to the cause(s) and type(s) of corrosion,
and, finally, propose possible
solutions for the problem, indicating which
of the solutions is best and why. Submit a
report that addresses these issues.