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EXPERIMENT MODULE
CHEMICAL ENGINEERING EDUCATION LABORATORY
ELETROCHEMICAL CORROSION
(KOR)
CHEMICAL ENGINEERING
FACULTY OF INDUSTRIAL TECHNOLOGY
INSTITUT TEKNOLOGI BANDUNG
2018
INSTRUCTIONAL LABORATORY
CHEMICAL ENGINEERING FTI - ITB
MODUL KOROSI ELEKTROKIMIAWI (KOR)
KOR – 2018 2
Contributors:
Dr. Isdiriayani Nurdin, Dr. Hary Devianto, Dr. Ardiyan Harimawan, Robby Sukma
Dharmawan, Jeffrey Pradipta W, Darien Theodric
INSTRUCTIONAL LABORATORY
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TABLE OF CONTENTS
TABLE OF CONTENTS ............................................................................................................ i
LIST OF FIGURES ................................................................................................................... ii
LIST OF TABLES ................................................................................................................... iii
CHAPTER I PREFACE ............................................................................................................ 1
CHAPTER II EXPERIMENT GOALS AND OBJECTIVES ................................................... 2
2.1. Experiment Goals............................................................................................................ 2
2.2. Experiment Objectives .................................................................................................... 2
CHAPTER III EXPERIMENTAL DESIGN ............................................................................. 3
3.1. Perangkat dan Alat Ukur ................................................................................................. 3
3.2. Materials/Chemical Substance ........................................................................................ 3
3.3. Experimental Condition .................................................................................................. 3
3.3.1. Constant Variables ....................................................................................................... 3
3.3.2. Free Variables .............................................................................................................. 4
3.3.3. Bound Variables........................................................................................................... 4
3.4. Equipment Layout ........................................................................................................... 4
CHAPTER IV WORKING PROCEDURE ............................................................................... 5
4.1. Preparation ...................................................................................................................... 5
4.4. Main Experiment ............................................................................................................ 6
Bibliography .............................................................................................................................. 7
APPENDIX ................................................................................................................................ 8
APPENDIX A RAW DATA TABLE ....................................................................................... 9
APPENDIX B CALCULATION PROCEDURE .................................................................... 10
APPENDIX C LITERATURE SPECIFICATION .................................................................. 11
APPENDIX D .......................................................................................................................... 12
INSTRUCTIONAL LABORATORY
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MODUL KOROSI ELEKTROKIMIAWI (KOR)
KOR – 2018 ii
LIST OF FIGURES
Figure 1. Equipment layout........................................................................................................ 4
Figure 2. Experimental flow diagram. ....................................................................................... 6
Figure 3. Experiment result (a) Fe-Zn (b) Fe-Cr. .................................................................... 10
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LIST OF TABLES
Table 1. Experimental data. ....................................................................................................... 9
Table 2. Standard potentials of some metals. .......................................................................... 11
INSTRUCTIONAL LABORATORY
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CHAPTER I
PREFACE
Corrosion is an event where material is damaged due to its interaction with its surroundings.
Industrial equipment made from metal if exposed to various aggressive environments can get
corroded. Corrosion in a chemical plant can cause substantial losses such as equipment
damage, halt of processes during equipment maintenance due to corrosion, leakage of raw
materials/intermediate products/end products with additional potential for environmental and
plant-related hazards. Therefore, the corrosion process needs to be studied to determine the
proper way of control.
Naturally, metals in oxidative environments tend to oxidize. This tendency is expressed as a
standard equilibrium potential of cation-metal reduction/oxidation reactions. The comparison
of various metal tendency to oxidize is expressed by standard potential series (electromotive
force, emf-series)
There are several methods of corrosion control that can be applied to metal equipments.
Corrosion control methods that apply basic electrochemical principles are cathodic protection,
anodic protection, and addition of inhibitors. The working principle of cathodic protection
and anodic protection is to change the metal potential to reduce the corrosion rate which is
proportional to the flow of electric current. The addition of inhibitors aims to reduce the
active surface area of the anode or cathode.
INSTRUCTIONAL LABORATORY
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CHAPTER II
EXPERIMENT GOALS AND OBJECTIVES
2.1. Experiment Goals
The goal of the experiment is to understand eletrochemical corrosion on metal and how to
control it.
2.2. Experiment Objectives
In this practicum, students are expected to identify:
1. Potential-Current Diagram (Evans Diagram) from pair of electrodes in certain
solution, also determination of metals’ function as cathode or anode.
2. Corrosion control method (cathodic/anodic protection, or mixed)
3. Influence of cathode/anode cross-sectional area and variation of electrolyte
concentration to corrosion rate
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CHAPTER III
EXPERIMENTAL DESIGN
3.1. Perangkat dan Alat Ukur
Equipments used in the experiments are:
a. Beaker glass (500 mL)
b. Plate electrode of carbon steel, aluminum, copper, and stainless steel, each with cross-
sectional area of 0,25 (0,5 x 0,5) cm2 dan 25 (5 x 5) cm
2
c. Variable resistance 0 – 10 k
d. Amperemeter
e. Voltmeter
f. Copper cable
g. Saturated standard electrode of Cu/CuSO4
h. Volumetric flash (1000 mL)
i. Measuring pipette 5-10 mL (as needed)
j. Funnel
3.2. Materials/Chemical Substance
Followings are materials/substance needed:
a. H2SO4 98%
b. Solid KOH/NaOH
c. Aqua dm
d. CuSO4
e. Isolator Tape
3.3. Experimental Condition
Experimental condition consists of constant, free, and bound variables.
3.3.1. Constant Variables
a. Room ambient pressure (660 – 700 mmHg)
b. Room temperature (23 – 28 oC)
c. Electrolyte volume (250 mL)
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d. Distance between electrodes (1 cm)
e. Types of electrodes and electrolytes
3.3.2. Free Variables
a. Electrolyte type and concentration (H2SO4 and NaOH solution with various
concentrations)
b. Coupling of different electrode types (carbon steel, aluminum, copper, stainless
steel)
c. Comparison of electrode cross-sectional area (anode area/cathode area : 1/1, 1/25,
25/1)
3.3.3. Bound Variables
a. Current
b. Electrode potential differences (cathode and anodes)
3.4. Equipment Layout
The layout of equipments used in this experiment is show by Figure 1. The layout consists of
intentiostatic layout with variation of resistance.
Figure 1. Equipment layout.
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CHAPTER IV
WORKING PROCEDURE
The working procedure of electrochemical corrosion module consists of two main steps:
1. Preparation
a. Preparation of electrodes
b. Preparaton of electrolyte solutions
c. Equipment assembly
2. Main Experiment
Includes the making of Evans diagram and the analysis.
4.1. Preparation
a. Preparation of electrodes
Two electrodes (according to assignment) along with Cu standard electrodes are
cleaned using abrasive paper from the lowest grade up to 1200 CW under flowing
water. Then the electrodes are washed with aqua dm and dried before use.
b. Making of Electrolyte Solutions
The steps of electrolyte preparation depend on the type of electrolyte used (as
assigned).
i. H2SO4 Solution
H2SO4 solution is made by taking a volume of H2SO4 using a measuring
pipette and filler. The solution is then fed into a quantity of water in a 500 mL
beaker glass The H2SO4 solution is introduced into the aqua dm slowly. Then
put the solution into the flask and add aqua dm until the solution reaches the
boundary mark in the flash.
REMEMBER : Pour H2SO4 to water, not the other way around!
ii. KOH/NaOH Solution
The solid KOH/NaOH is weighed as needed. The solid is then fed into a
beaker containing a certain amount of water. The KOH solution is put into a
flask and aqua dm is added until the solution reaches the boundary mark of
flask.
c. Equipment Assembly
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The equipments are assembled according to the layout in Figure 1.
4.4. Main Experiment
Record the voltage of the cell and electric current when the variable resistance is set to zero.
After that, the current is decreased by slowly increasing the variable resistance. Do changes
in cell resistance several times until the current is no longer readable by the amperemeter.
Record the current and voltage of the cell each time its resistance changes. After that, plot the
experiment result as Evans diagram. The experimental flow diagram is shown in Figure 2.
Start
Preparation of Equipments
Scrub electrodes with abrasive paper
Scrub standard electrodes with abrasive paper
Take H2SO4 96% using pipette
Wash with aqua dmFill tube with saturated CuSO4
solutionAdd an amount of aqua dm to
beaker glass
Add aqua dm until the boundary mark of volumetric
flask
Assemble the equipment
Set resistance to 0
Read starting V & I
Do variations on the resistance
Read V & I
Selesai
n-sequence of i reading?
Figure 2. Experimental flow diagram.
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Bibliography
Jean Besson et Jacques Guitton, 1972, Manipulations d’electrochimie, introduction a la
theorie et a la pratique de la cinetique electrochimique, Paris: MASSON & CIE.
Jones, D.A., 1992, Principles and Prevention of CORROSION, Macmillan Publishing
Company.
Prentice, G., 1991, Electrochemical Engineering Principles, Prentice-Hall International, Inc.
INSTRUCTIONAL LABORATORY
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APPENDIX
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APPENDIX A
RAW DATA TABLE
Example of experimental table used in the experiment is shown below.
EXAMPLE
Run number :
Electrode 1 (area) :
Electrode 2 (area) :
Electrolyte type and concentration :
Table 1. Experimental data.
I (mA) V1 (mV) V2 (mV)
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APPENDIX B
CALCULATION PROCEDURE
Figure 6 shows the Evans diagram obtained from the experiment. In both cases with Fe-Zn
and Fe-Cr pair electrodes, the corrosion was controlled by cathodic reaction. Note that in the
case of Fe-Cr, the maximum current of 0.23 mA is centered on the Fe anode of 0.03 cm2 to
produce an alarming deep-pit corrosion. In contrast, with Fe - Zn pairs, a current of 0.12 mA
is divided over a 25 cm2 Zn anode. The corrosion that occurs in these electrode pairs is even
corrosion. Therefore, the thickness decrease of electrodes due to corrosion runs very slowly.
Figure 3. Experiment result (a) Fe-Zn (b) Fe-Cr.
In experimental conditions with a closure of 50% cathodic or anodic surface area, a change in
corrosion rate is indicated by a decrease in current. The result can be seen in Figure 6 with
dashed lines.
From Evans diagram, we can conclude that:
a. Corrosion reaction type : cathodic/anodic control
b. Metal that function as anode and cathode
c. Maximum corrosion rate, calculated from ianodic max (= Imax/anode area) using Faraday
equation (
)
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APPENDIX C
LITERATURE SPECIFICATION
C.1. Standard Potential Series
Table 2. Standard potentials of some metals.
½ Cell Reaction Standard Potential (V)
Au3+
+ 3e- Au +1.420
O2 + 4H+ + 4e
- 2H2O +1.229
Pt2+
+ 2e- Pt +1.2
Ag+ + e
- Ag +0.800
Fe3+
+ e- Fe
2+ +0.771
O2 + 2H2O + 4e- 4(OH
-) +0.401
Cu2+
+ 2e- Cu +0.340
2H+ + 2e
- H2 0.000
Pb2+
+ 2e- Pb -0.126
Sn2+
+ 2e- Sn -0.136
Ni2+
+ 2e- Ni -0.250
Co2+
+ 2e- Co -0.277
Cd2+
+ 2e- Cd -0.403
Fe2+
+ 2e- Fe -0.440
Cr3+
+ 3e- Cr -0.744
Zn2+
+ 2e- Zn -0.763
2H2O + 2e- H2 + 2(OH
-) -0.828
Al3+
+ 3e- Al -1.662
Mg2+
+ 2e- Mg -2.363
Na+ + e
- Na -2.714
K+ + e
- K -2.924
C.2. Electrical Conductivity of Metal
Find the conductivity of used metal! (as assigned)
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APPENDIX D
JOB SAFETY ANALYSIS
No Material Material Properties Countermeasures
1 Sulfuric
Acid
(H2SO4)
Very corrosive
Hazardous if
inhaled
Hazardous to
skin (can cause
burn)
Can cause
respiratory
iritation
Very toxic
Dangerous in
aquatic
environment
Boiling point =
270°C
Colorless
Molecular weight
= 98,08 g/mol
Smell = has a
little bit of
character
Solubility in
water : soluble,
exothermic
Inhaled:
Get aids. Wash immediately
with water. If hard to inhaled,
quickly get oxygen. Don’t
use mouth-to-mouth
resuscitation.
Swallowed:
No need to vomit. If victim is
conscious, give 2 – 4 glass
of milk or water. Get aid
immediately.
Skin contact:
If contacted with skin or hair,
immediately wash with soap
and water for 15 minutes. Get
aid.
Eye contact:
Wash with flowing water for
at least 30 minutes. Don’t let
victim close or wipe the eyes.
Work in fume hood
2 Copper
(II)
Sulfate
(CuSO4)
Odorless
Can cause skin
eye, respiratory
and digestive
system
iritation, and
also damage in
internal organ.
Boiling point =
150°C
Solid
Molecular weight
= 249,69 g/mol
If inhaled, get fresh air
immediately
Water contact: Check and
remove any contact lense.
Wash eye with flowing
water for at least 15 minutes.
Can use cold water. Get
medical aid.
Skin contact: wash skin with
large amount of water. Close
iritated skin with emolient.
Clean shoes before use.
Get medical aids.
3 Water Molecular
weight =
18,02 g/mol
Boilig point =
100°C
Density = 1
gr/cm3
Specific gravity
Inflammable
Odorless
Colorless
Clean with dry cloth in case
of spill.
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: 1
pH : 7
Boiling point =
100 oC
Melting point :
0 oC
Accidents that may happen Penanggulangan
Student slip on material spill Treat material carefully, especially sulfuric acid
(H2SO4) and call laboratory assistant for help in
handling the cleaning.
Perlengkapan keselamatan kerja
Gloves Lab coat Mask Goggle
Safety Working Procedure
1. Materials and equipment checking:
Ensure equipments are in good condition
Ensure taking the correct material and closing it well
2. Experiment
Ensure the equipments are assembled as layout
Immediately dry material spill.
3. After experiment
Make sure all equipments are turned off and electrical cables are plugged out.
Make sure tables and floors are cleaned from leakage/spill.
Asisten Pembimbing Koordinator Lab TK