The document contains a table of numerical data with stress values in the first column and strain values in the second column, suggesting it is a stress-strain curve for a material. It lists over 200 pairs of stress and strain values ranging from 1.00E+009.54E-04 to 3.81E+024.54E-03, with the stress increasing approximately linearly with strain over most of the range. The high number of data points and large range indicate it is providing a detailed characterization of the material's mechanical properties under loading.
10. solve it using Excel Solver for obtaining the optimum minimum
cost for the 5-month horizon.
Your case study report must contain
A.Objective function
B.Constraints
C.Excel Solver output (if you don’t attach Excel output with
your report you will be awarded ‘0’ for the case)
Case study is an individual assignment; please note that
cheating on the assignment will not be tolerated. All the
students whose reports look similar will be awarded ‘0’; Repeat
violators will be reported to the Dean of Students. NO
EXCEPTIONS.
Month
Units
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Units
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Subcontracted
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0100
1
38. Experiment #9- Corrosion of Metals
Abstract:
Studying the corrosion of materials and applying the prevention
of corrosion is important and can help aid the economy. If used
properly, inhibitors can help reduce the rate of corrosion on
materials. This experiment is designed to help determine how
inhibitors make a difference in corrosion rates by using two
types of metals. Corrosion has been at fault in many accidents
involving bridges, highways, and structures seen in everyday
life. By having a little knowledge of material behavior and
corrosion it is possible to help save large amounts of waste and
accidents due to corrosion. Tests for corrosion are made in
order to come up with a corrosion resistant material and better
inhibitors. the use of a EG&G Versa Stat machine is made in
order to determine how long a certain material will last under a
corrosive environment. The machine will also help in
determining the rate of corrosion with and without an inhibitor,
while also determining the degree of effectiveness of the
inhibitor. The samples used for this specific experiment are
1018 steel and brass.
Description of Work:
The experiment is started by preparing the samples of 1018
steel and brass by polishing them using different weight
polishing compounds. The samples are then taken after
completion of polishing and placed under a microscope in order
to ensure proper polishing and to take initial photographs. The
dimensions of the samples are then measured and their cross
sectional areas are then calculated. A 3.5% saline solution is
poured into the electrochemical cell. The first specimen is then
connected to the colmel standard reference electrode and
counter electrode while making sure that the counter electrode
39. and the surface of the sample are parallel. The wiring is as
follows: the green wire connects to the working electrode, the
red wire connects to the counter electrode, and the white wire
connects to the reference electrode. The computer on the EG&G
Versa Stat machine is then set up according to the parameters of
the material being used in the experiment. Once the test is
complete the data must be saved on a disk and verified on
another computer in order to ensure proper storage of the data.
An image of the corroded sample is then taken in order to be
compared to the initial photograph of the uncorroded sample.
The sample is then taken and polished once again to remove all
of the corrosion accumulated on it’s surface from the previous
test. The test is then run once again, but with antifreeze as the
inhibitor mixed with the saline solution. Photographs must be
once again taken after the corrosion test has been completed.
The same procedure must be repeated for the other sample once
the first in complete. This data is to be collected to determine
the corrosion rate of the metals and degree of effectiveness of
the inhibitor.
Results:
Based on the data collected it is apparent that the samples
placed in the saline solution had much more corrosion and had
corroded at a higher rate than the samples with the inhibitor.
The samples in the saline solution corroded at an increasing
rate, while the samples in the saline solution with an inhibitor
corroded at a decreasing rate, showing how the inhibitor proved
useful. The brass corroded at at rate of approximately 18.0mpy
in the saline solution and at approximately 14.5mpy in the
solution with an inhibitor. The steel sample corroded at a rate of
approximately 10.0mpy in the saline solution, and at a rate of
approximately 0.7 mpy in the solution with the inhibitor. As one
can see from these results, it is made apparent that the use of an
inhibitor is extremely important in reducing rates of corrosion.
Both of the samples used proved to have good resistance to
40. corrosion signifying a good use in industry. The sources of error
in this experiment could have come been attributed to many
factors. Some being as follows: There could have been under-
polished samples that had initial corrosion that attributed to an
increase in corrosion rate, the area measurements used in the
calibration of the machine could have been incorrect, the
position of the sample in the solution could have been incorrect,
The wiring could have been incorrect, and the Parameters set on
the computer could have been incorrect leading to incorrect
readings.
EXPERIMENT #9
CORROSION OF METALS
Objective
The objective of this experiment is to measure the corrosion
rate of two different metals and
to show the effectiveness of the use of inhibitors to protect
metals from corrosion.
Background
The importance of corrosion can be seen in daily life. Corrosion
causes accidents in industry,
on highways, and in homes. It is wasteful financially, costing
industrialized nations 4-5% of
their gross domestic products annually. A little knowledge of
electrochemistry, material
science and corrosion could save nations some 25% of this loss.
Corrosion engineering is the application of science and art to
prevent or control corrosion
damage in a safe and economical manner. To perform this
41. function properly, the corrosion
engineer must rely on experimental research. This is because
the major aspects of corrosion
engineering are largely empirical in nature. A body of theory
exists that can be very helpful
in solving corrosion problems, but in the final analysis, most
decisions are based on the
results of empirical tests.
Corrosion tests are conducted for a number of reasons
including:
1. Establishing corrosion mechanisms.
2. Defining corrosion resistance of materials and how to
develop new corrosion resistant
alloys.
3. Estimating service life of equipment.
4. Developing corrosion protection processes.
5. Defining the critical potential values for materials in various
environments.
Theory
Anodes and Cathodes:
In analyzing corrosion, the first thing that must be determined
is whether a metal reacts with
its environment. If so, the nature of the reaction must be
understood. It is generally accepted
that corrosion processes are caused by the formation of
electrochemical cells. The
electrochemical reactions in these cells can be divided into two
reactions:
1. Anodic reactions
2. Cathodic reactions
where each reaction is called a half-cell reaction. In the anodic
42. reaction, metal goes into
solution as an ion. The reaction is generally written as:
M --> Mn+ + ne-
where M is a metallic element, e- is an electron and n is the
valence of the metal as an ion.
An example of this is Zinc where:
Zn --> Zn2+ + 2e-
In the cathodic reaction, electrons provided by the anode, flow
through the metal until they
reach the cathode where they can be combined with positively
charged ions. In acidic
solutions this reaction is:
2H+ + 2e- --> 2H --> H2(gas)
and in neutral solutions the reaction is:
O2 + 2H2O + 4e
- --> 4OH-
Both the anodic and cathodic reactions must occur
simultaneously for a corrosion process to
proceed. If both reactions are not occurring then a charge
builds up and the corrosion process
stops. The anodic reaction is generally the simple case of a
metal going into solution.
However a variety of cathodic reactions are encountered
depending on the conditions of the
process involved. Table 1 shows several examples of different
43. cathodic reactions. Note that
in all of the cathodic reaction electrons are absorbed.
Table 1 - POSSIBLE CATHODE REACTIONS IN DIFFERENT
GALVANIC CELLS
–––––––––––––––––––––––––––––––––––––––––––––––––––––
–––––––––––––––––
Cathode Reaction Example
2H+ + 2e- --> 2H Acid
Solution
s
O2 + 2H2O + 4e
- --> 4OH- Neutral and alkaline solutions
O2 + 4H
+ + 4e- --> 2H2O Using both O2 and H
+ in acid solutions
M3+ + e- --> M2+ When Ferric ions are reduced to ferrous
44. M2+ + 2e- --> MO When iron is placed in a Cu salt solution
the
electron from solution of the iron reduces Cu
ions to metallic Cu
–––––––––––––––––––––––––––––––––––––––––––––––––––––
–––––––––––––––––
The electrode potential in the electrochemical cell
When an ideal metal is placed in an electrolyte, an electrode
potential develops that is related
to the tendency of the material to give up electrons. To measure
this tendency, we measure
the potential difference between the metal and a standard
electrode using a half-cell.
The standard reference electrode is a half cell with a known
constant potential. Different
standard reference electrodes are used depending on the
solution environment. Some
standard electrodes are the standard hydrogen electrode (SHE)
and the saturated calomel
electrode (SCE).
45. Standard expressions for corrosion rate
In most cases, aside from contamination problems, the primary
concern where corrosion is
present, is the life (usually in years) of metals in question. A
good corrosion rate experiment
should include:
1. Familiar units.
2. Easy calculations with a minimum opportunity for errors.
3. Ready conversion of data to life in years.
4. Penetration.
5. Whole numbers without cumbersome decimals.
Mils penetration per year (mpy) is the most commonly used
corrosion rate expression in
the United States. One formula used to calculate the corrosion
rate is:
534 x W
mpy = ––––––––
D x A x T
46. where,
W = weight loss (gms)
D = density of the specimen, g/cm3
A = area of specimen, sq. in.
T = exposure time, hr.
The corrosion rates of resistant materials generally range
between 1 and 200 mpy. The
relative corrosion resistance of a material can be evaluated
using the following criteria:
Relative Corrosion Resistance mpy
outstanding <1
excellent 1-5
good 5-20
fair 20-50
poor 50-200
unacceptable >200
Consider a car engine block with and without the addition of
antifreeze, as an example of a
corrosion rate problem. Engine blocks are generally made from
low carbon steel that
corrodes when exposed to tap water. This is the brown rust that
is often seen in cooling
47. systems containing water only. The corrosion reactions for low
carbon steel are:
Fe --> Fe2+ + 2e-
Fe2+ --> Fe3+ + e-
O2 + 2H2O + e
- --> 4OH-
2Fe + 2H2O + O2 --> 2Fe
2+ + 2OH- --> 2Fe(OH)2
2Fe(OH)2 + H2O + 1/2 O2 --> 2Fe(OH)3 (rust)
The electrochemical technique is used to study the corrosion
rate of low carbon steel in tap
water instead of using the weight loss technique. This is
because the former is a very rapid
method of obtaining data while the latter technique is a very
48. lengthy process. In the
electrochemical process the corrosion rate is measured by
measuring the current density, J:
I
J = ––
A
where I is the current in microamps (µA) and A is the area in
cm2. The corrosion rate can be
calculated from this using the relationship:
1 mpy = (1/n ) J
where n is the valence of the metal involved (M --> Mn+ + ne-).
PROCEDURE
CAUTION: BE SURE YOU UNDERSTAND HOW TO
OPERATE THE EQUIPMENT
BEFORE BEGINNING THE EXPERIMENT
If you are not familiar with the equipment ask for help from
your instructor. DO NOT
START INDISCRIMINATELY MAKING ADJUSTMENTS TO
49. THE EQUIPMENT.
Your group will be provided with samples of 1018 steel and
brass. Prepare the sample
(metal exposed side) for metallographic observation
(polish/grind using 400 grit, 600 grit
sandpaper and 1 micron powder). Check the specimens under
the microscope to be sure that
they are well polished. Observe the surface of each specimen
before and after corrosion
takes place. Take photos.
CAUTION: The equipment used to measure corrosion rates is
very delicate. Use extreme
care when handling.
Pour about 400cc tap water (room temperature) into the beaker
that makes up the
electrochemical cell and add approximately one teaspoon of salt
to form a solution. Then
place one prepared (steel or brass) specimen in the cell setup
with the calomel standard
reference electrode and the counter electrode. Check to be sure
that the counter electrode
and the sample surface are parallel (not touching).
50. Connect the leads from the EG&G VersaStat to the
electrochemical cell. The Green wire
attaches to the working electrode (the sample), the Red wire
attaches to the counter
electrode, and the White wire attaches to the reference
electrode.
If the machine is not already on, boot up the computer and at
the DOS C:> prompt type:
corr [ENTER].
When the title screen comes up hit any key to display the Main
menu. Pick “SetUp“ from the
main menu to display the Set up menu. Pick “Get Set Up”.
You will then be asked to “Enter setup filename for recall.”
Type: 227L [ENTER].
The screen will now display the test parameters to be used for
your experiment. Your group
will have to enter the correct sample area and specimen density
in their respective fields on
51. the test Setup Screen.
Once the correct test parameters have been entered for your
specimen, your group is ready to
run a test. Choose the Run command from the menu and turn the
Cell Switch located on the
front of the EG&G Versa Stat to the ON position. A plot of your
test will appear on the
computer screen once the test begins. The test runs for 15
minutes.
When the test stops, turn the Cell Switch to the OFF position.
Save your data to a 3.5”
floppy before beginning any further tests. Put a 3.5” floppy disk
into the A drive. To save
your data first save your data on the C drive using the “Save”
command in the “File”
menu. Next recall your data using the “Get Data” command in
the “File” menu. Finally,
transfer the data to your diskette in the A drive by choosing the
“Export Data” from the
“File” menu. Type in a file name for your data including an A
drive path. (For example, you
can type: a:steel).
52. Repeat this procedure for the other metal (steel or brass)
sample.
Next put about 400cc of the prepared antifreeze/water mixture
(50% ethylene glycol) into
the electrochemical cell and repeat the experiment for the
remaining samples. Note the
corrosion inhibiting effect of the antifreeze. Normally, when
antifreeze is added in small
concentrations to an environment, the corrosion rate decreases.
In a sense, an inhibitor can
be considered a retarding catalyst. The effectiveness of an
inhibitor can be measured based
on:
Corrosion rate without inhibitor
Degree of effectiveness of inhibitor = ––––––––––––––––––––
––––––
Corrosion rate with inhibitor
when a rate is determined using the mpy equation once the rate
has plateaued.
Glossary of Terms
53. Understanding the following terms will help in understanding
this experiment.
Anode. The electrode in an electrochemical cell that oxidizes,
giving up electrons to an external
circuit and ions into solution during corrosion.
Anodic reaction. The oxidation reaction occurring at the anode
in an electrochemical cell.
Aqueous corrosion. Dissolution of a metal into a water-based
environment.
Cathode. The electrode in an electrochemical cell that accepts
electrons from an external circuit and
where a by-product is produced during corrosion.
Cathodic reaction. The reduction reaction occurring at the
cathode in an electrochemical cell.
Composition cells. Electrochemical corrosion cells produced
between two materials having a
54. different composition. Also known as a galvanic cell.
Corrode. Lose material to a surrounding solution in an
electrochemical process.
Electrochemical cell. A cell in which electrons and ions can
flow by separate paths between two
materials (a cathode and an anode), producing a current which
in turn leads to corrosion or plating.
Electrochemical corrosion. Corrosion produced by the
development of a current in an
electrochemical cell which removes ions from the material.
Electrode potential. Related to the tendency of a material to
corrode. The potential is the voltage
produced between the material and a standard electrode.
Electrolyte. The conductive medium through which ions move
to carry current in an electrochemical
cell.
Electromotive force series. The arrangement of elements
according to their electrode potential, or
their tendency to corrode. A listing of half cell reaction
55. voltages.
Galvanic corrosion. Corrosion produced by the electromotive
force associated with two dissimilar
metals.
Galvanic series. The arrangement of alloys according to their
tendency to corrode in a particular
aqueous environment.
Inhibitors. Additions to the electrolyte that preferentially
migrate to the anode or cathode, cause
polarization, and reduce the rate of corrosion.
Oxidation reaction. The anode reaction, by which electrons are
given up to the electrochemical cell.
Oxygen electrode. The cathode reaction by which electrons and
ions combine to produce OH- ion
groups in the electrolyte.
Passivation. Producing strong anodic polarization by causing a
protective coating to form on the
anode surface and interrupt the electric circuit.
56. Reduction reaction. The cathode reaction, by which electrons
are accepted from the electrochemical
cell.
Water electrode. The cathode reaction by which electrons and
ions combine to produce water in the
electrolyte.
Write Up
Write a memo report including the rate of corrosion for all
samples in mpy (once the
specimen's rate levels off), and the degree of effectiveness of
the inhibitor. Graph the current
density versus time. Discuss the sources of error in this
experiment.
MSE 227L Name ________________________
Corrosion of Metals
Poor Fair Average Good Excellent
Memorandum Format Used 1 2 3 4 5
57. Spelling, grammar, & punctuation correct 1 2 3 4 5
Report includes: Poor Fair Average Good Excellent
Discuss rate of corrosion for all samples in
mpy (once the specimen's corrosion rate
levels off). Discuss current density vs.
time. Show calculation for mpy.
1 2 3 4 5
Discuss the degree of effectiveness of the
inhibitor. Show calculations.
1 2 3 4 5
Graph the current density versus time.
Overlay graphs for comparison. Include
more than 1 graph.
4 8 12 16 20
Include table of results, measurements,
significant parameters obtained or used in
this lab. (relevant information)
58. 1 2 3 4 5
Discuss sources of error in this experiment. 1 2 3 4 5
Attach photos of steel and brass samples
(comparison of before and after testing in
saltwater and antifreeze solution)
1 2 3 4 5
Column Subtotals
Poor Fair Average Good Excellent
Overall level of effort apparent 1 2 3 4 5
Quality of graphs 1 2 3 4 5
Quality of abstract 1 2 3 4 5
Quality of work description 1 2 3 4 5
Quality of conclusions 1 2 3 4 5
Column Subtotals