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Galvanic Corrosion Experiment
Introduction
In this experiment, the students will analyze the various situations that can affect galvanic
corrosion. The two metals used in this lab were Zinc and Copper, where Zinc is the anode and
Copper is the cathode in this experiment.
Procedure
Potential reading:
1. Measure and record the width of the Zinc and Copper electrodes, as well as the volume of
water.
2. Submerge half of the Copper and Zinc electrodes, facing each other about 50 mm apart
(measure actual separation distance between the metals, S, and actual immersion depths, D, to +1
mm). This is called the “starting position” hereon.
3. Connect the + (red) terminal of the multimeter to the Copper, and the – (black or “com”)
terminal of the multimeter to the Zinc. Measure the difference of potential (AV) between the
Copper and Zinc and wait a few seconds until it stabilizes.
4. Now vary S as well as the degree of immersion, D. Try four different arrangements. Record
configuration and AV after each change.
Current reading:
5. Return the electrodes to the starting position. Configure the multimeter as an Ammeter (in mA
range). Measure the current flow, I, between the Zinc and Copper.
6. Measure I for the combinations (a) and (b) of immersed depth of Zinc and Copper as shown
below. Measure with accuracy of +1 mm the actual submerged depths and each electrode width.
a) Zinc about 1/8“(roughly 3 mm) submerged and Copper is halfway submerged.
b) Zinc is halfway submerged, and Copper is about 1/8“ (roughly 3 mm) submerged.
7. Return to the starting position and then change S (distance between the sheets) so that it is as
small as possible and as large as possible. Measure and record both current and distance in each
case.
8. Return the electrodes to the starting position.
9. Add 4 grams of NaCl to the bucket the current. water. Stir and dissolve completely and then
record
10. Add 40 grams more of salt to the bucket of water for a total of 44 grams. Stir and dissolve
completely and then record the current
1
Galvanic Corrosion Experiment
Data and Results
Table 1: Measurements
Water Volume (L)
3.72
Step#
2-3,5,8
4
6
7
10-Sep
Position
Start Position
ΔV 1
ΔV 2
ΔV 3
ΔV 4
I (a)
I (b)
I (S smallest)
I (S largest)
I (4g Salt)
I (44g Salt)
Zinc Width (cm)
1.85
Copper Width (cm)
2.9
Table 2: Data Collected in Lab
Voltage (V) Current (mA) D of Zn (cm)
940
265
6.6
954
6.6
939
4
925
4
942
4
260
0.3
63
6.6
256
6.6
240
6.6
0.2
6.6
1.09
6.6
Table 3: Area of Zn and Cu, and Ar
Azn (cm^2)
Acu (cm^2)
Ar =Azn/Acu
24.42
23.2
1.052586207
24.42
23.2
1.052586207
14.8
23.2
0.637931034
14.8
2.9
5.103448276
14.8
33.06
0.447670901
1.11
23.2
0.047844828
24.42
1.74
14.03448276
24.42
23.2
1.052586207
24.42
23.2
1.052586207
24.42
23.2
1.052586207
24.42
23.2
1.052586207
Sample calculation:
Azn = 2 * (Zinc width * D of Zn)
= 2 * (1.85 * 6.6)
= 24.42 sq. cm
Acu = 2 * (Copper width * D of Cu)
= 2 * (2.9 * 4)
= 23.3 sq. cm
Ar = Azn/Acu
= 24.42/23.3
= 1.0526
2
D of Cu (cm)
4
4
4
0.5
5.7
4
0.3
4
4
4
4
S (cm)
5
5.5
9.1
9.1
13
5
5
1.5
23
5
5
Galvanic Corrosion Experiment
Table 4: CRZn in mpy
CRZn (cm/h)
CRZn (mpy)
1855.60
6399.62
40052.93
138135.30
441.14
1521.42
1792.58
6182.28
1680.54
5795.89
1.40
4.83
7.63
26.32
Sample calculation:
CRZn (cm/h) = Current * Atomic Mass / (2*Faraday’s constant * Density * Azn)
= 265 * (1000*65.38) / (2 * 26.80148 * 7.133 * 24.42)
= 1855.60 cm/h
CRZn (mpy) = CRZn (cm/h) * 8760 / (1000*2.54)
= 6399.62 mpy
Current (mA)
0.2
1.09
Moles
0.0685
0.7534
Table 5: Liquid Electrical Conductivity
Initial σ (ohm^-1 cm^-1)
M (mol/L)
Extra σ (ohm^-1 cm^-1)
0.018412
0.0007
0.0020253
0.202534
0.0007
0.0222787
Sample calculation:
4g of NaCl * 1 mole / 58.4 mole = 0.0685 moles
M = 0.685 moles / 3.72 L
= 0.01841 mol/L
Extra σ = M * 0.11
= 0.01841 * 0.11
= 0.0020253 ohm^-1 cm^-1
σ = Initial σ + Extra σ
= 0.0007 + 0.0020253
= 0.0027253 ohm^-1 cm^-1
3
σ (ohm^-1 cm^-1)
0.0027253
0.0229787
Galvanic Corrosion Experiment
CRZn vs S
140000.00
138135.30
CRZn (mpy)
120000.00
100000.00
80000.00
60000.00
26.32
40000.00
1521.42
4.83
6399.62
20000.00
6182.28
5795.89
0.00
0
5
10
15
20
25
S (cm)
Figure 1: CRZn vs S
CRZn vs Ar
16
14.0345
14
12
Ar
10
1.0526
1.0526
1.0526
8
6
4
1.0526
2
1.0526
0.0478
0
0
20000
40000
60000
80000
100000
CRZn (mpy)
Figure 2: CRZn vs Ar
4
120000
140000
160000
Galvanic Corrosion Experiment
CRZn vs σ
32.00
27.00
CRZn (mpy)
22.00
17.00
12.00
7.00
2.00
0.0025
0.0075
0.0125
0.0175
0.0225
0.0275
σ (ohm^-1 cm^-1)
Figure 3: CRZn vs σ
Conclusion
In this experiment, it was found that CRZn increases as the area of Zinc decrease, which
is the anode of galvanic couple. Moreover, as the distance between the two metals increases, The
CRZn value decreases. As of the liquid conductivity in galvanic corrosion, the more NaCl added
to the water, the higher liquid conductivity. Galvanic corrosion protection methods varies and
one method is by choosing materials that has similar corrosion capacities.
5
0000 6812.665909
4892,36267
50002782.0647 BR. 64764
983.900953
0
0
in
5
0.025
0.0229787
0.02
0.015
0.01
uais
0.005
0.00272253
0
0
1000
2000
6000
7000
B
3000 4000 5000
CRZn (mpy)
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