Corrosion Rate and Galvanic Series Measurements Results Report

This report presents an analysis of corrosion rates and galvanic series measurements, focusing on iron and galvanized iron. The study determines corrosion rates through weight loss and surface area analysis, highlighting the differences in corrosion behavior between iron and galvanized iron. The galvanic series is constructed by measuring the voltage across different metals, revealing their relative reactivity and corrosion tendencies. The discussion section explains the observed results, emphasizing the cathodic protection provided by zinc in galvanized iron. The report further explores the relationship between surface area and corrosion rate, the impact of metal reactivity, and the significance of corrosion rate in structural design. It concludes with suggestions for corrosion prevention methods, such as using a combination of protective techniques. The report also answers questions related to corrosion rate's significance in structural design, current requirements for corrosion protection, and the effects of noble metal surface area on corrosion. Finally, it discusses three methods for preventing corrosion based on the galvanic series, supported by schematic diagrams, and addresses the placement of voltages on Pourbaix diagrams.

CORROSION RATE AND GALVANIC SERIES MEASUREMENTS
RESULTS
I. Corrosion rate determination
Specimen Surface area(mm 2) Initial weight (gm) Final weight (gm) Weight loss ( gm)
Iron nail 3785.1 46.413 44.475 1.938
Galvanize
d iron
661.3 4.569 4.037 0.532
Table 1: nails dimensions and weight.
II. Construct galvanic series
Metal copper Steel aluminum Titanium zinc magnesium
Measured
voltage
(mV) 164 285 758 120 185 1.548
Table 2: Galvanic series
ANALYSIS
Corrosion rate determination
 Iron nail
D= 7.86g/cm3
corrosion rate ( mm
year )= 87.6∗1.938
7.86∗3785.1∗( 24∗7 ) =3.4∗10−5 mm/ year
 Galvanized iron
D= 7.85g/cm3
corrosion rate ( mm
year )= 87.6∗0.532
7.85∗661.3∗ (24∗7 ) =5.35∗10−5 mm/ year
CHARTS

Iron nail Galvanized iron
0
500
1000
1500
2000
2500
3000
3500
4000
0
0.5
1
1.5
2
2.5
Agraph of weight loss and surface area against
metals
Surface area (mm2)
Weight loss (gm)
Surface area (mm2)
Weight loss (gm)
Chart1: Corrosion rate determination
copper
steel
aluminium
Titanium
zinc
magnesium
0
100
200
300
400
500
600
700
800
Agraph of Measured voltage (mV) verses metals
Measured voltage (mV)
measured volatge (mV)
Chart2: Galvanic series
DISCUSSION OF RESULTS
Iron corrosion rate is higher than galvanized iron corrosion rate. This is because the corrosion of zinc is
very slow thus giving extended life to the base metal, iron. Zinc protects the galvanized iron from
corroding through cathodic protection. The galvanized iron corroded at a slow rate through the small
areas that are exposed to atmospheric conditions through damaged areas. On the other hand, iron corroded
at a faster rate since there was no mechanism that was used to protect it from corroding.
The data obtained from the corrosion rate used in plotting the chart of weight loss and surface area
indicate a direct relationship between the corrosion rate and surface area exposed to surrounding. When a

large surface area is exposed, rate of corrosion is higher and reduces for small surface area. Experimental
surface area of iron is larger than that of galvanized iron thus the rate of corrosion of iron was higher than
rate of corrosion in galvanized iron leading to more weight loss.
The galvanized experiment involved the measurement of the voltage across the electrodes (electrode
potential) that indicate a relationship between voltage and corrosion. The higher the ability of a metal to
give electrons, more voltage the metal will produce. The more voltage a metal gives, the higher its rate of
corrosion. Metals that are more reactive have the tendency of easily giving their electrons thus they
produce more voltage. These metals have higher corrosion rate than less reactive metals, noble metals. In
this case, aluminum has a higher tendency of giving off its electrons thus it produces more voltage than
other metals such as magnesium. Due to this, aluminum metal has a higher corrosion rate than
magnesium.
CONCLUSION
Understanding metals corrosion rate is of the essence for structural design. This enables one to understand
what materials are to be used in a given environment so as to ensure that they will serve the given purpose
appropriately. It is also critical to understand various methods that can be used to prevent corrosion of
metals.
Suggestion for improvement
In order to reduce the rate of corrosion of metals, we should use a combination of methods to prevent
corrosion. For instance, after galvanizing iron, we should use it together with another metal that has
almost a similar corrosion rate as the galvanized iron. This will greatly reduce metals corrosion rate.
Questions
1. What is the significance of corrosion rate and how will you incorporate this in structural
design?
The rate of corrosion is the speed at which a given metal deteriorates when exposed to a given
environment. The properties of the metal play a central role in determining corrosion rate of the metal.
Metals corrosion rate is important since it helps in determining the suitability of the metal to be used in
given environment.
Considering that corrosion leads to loss of metal strength, reduces its bond strength, reduces its shear
capacity, and also accelerates metal fatigue, it is of the essence to determine the rate of corrosion of a
metal during the structural designing phase of a project so as to ensure that the metals used in any design
are fit for the assigned purpose (Bell, 2018).
2. Calculate the total current requirement for a year to protect the steel nails corroding based
on the chemical formula in equation 1.
Mass=current∗8.65∗no . of years
mass=4.569 g∧ year=1

Current= mass
(8.65∗no . of years)= 4.569
8.65 =0.528 A
3. If the surface area of a more noble metal is doubled what will happen to the corrosion rate
when connected to a less noble metal? Explain whys.
Highly noble metals have higher potentials which lower its tendency to corrode. Doubling the
surface area of a noble metal increases the area of corrosion. But since the noble metal is
connected to a less noble metal, the rate of corrosion of the less noble metal will double. This is
because the noble metal will be drawing electrolytes from the less noble metal thus doubling the
tendency of the less noble metal to corrode (Bell, 2018).
4. Based on the galvanic series discuss 3 ways in which corrosion can be prevented. Explain
with schematic diagrams.
a) Breaking electrical connection between two metals by inserting a sized spacer between
them: This will prevent free flow of electrolytes between them.
b) Installing a sacrificial anode that is anodic to both metals used: The sacrificial anode will
corroded instead of metals.
c) Selecting materials with almost the same corrosion potential: For instance,
Stainless steel (+0.09)→ Tin(−0.26)→ Stainless steel( AISI 304 ), Active state (−0.29)→ Lead ¿
Magnesium (-1.36)
In this case, it would be better for one to select Stainless steel (AISI 304), Active state and Lead
rather than selecting stainless steel and Magnesium.
5. Using the voltages measured for each metal, show where the voltages are placed on
pourbaix diagrams on metals. PH of 3.5% solution is 7.
References
Bell, T. (2018). Corrosion Prevention for Metals. The Balance.