Investigation of the low carbon steel bends into different angles with dimension 50 mm X 20 mm and
then plated in Nickel bath at 3V for 25 minutes subjected to NaCl and H2SO4 corrosive environment.
This research investigated the corrosion resistance of nickel- plated and un-plated low carbon steel
and in a corrosive environment of H2SO4 and NaCl solutions. Weight loss method was used for
estimation the corrosion rate in the current study. Low carbon steel sample was nickel electroplated at
3V for 25 minutes. Plated and the un-plated carbon steel sample were subjected to H2SO4 and NaCl
environment for fifteen days. The electrode potentials, in mV (SCE), were measured every day.
Weight loss was determined at intervals of 2 days for the duration of the exposure period.
Electrodynamics experiment was performed. This provides the information that the potential drop was
in the range of -322 to -622 mV SCE for the 30-degree angle which shows more electronegative
potentials that it corrodes faster compared to sample 180 degree of potential range of -353 to -545
which denote reduced corrosion activity. The corrosion rate plots ascertain the corrosion behavior is a
sample of angle 30 and 180 degree.
The Tafel plots to determine the current densities were obtained, results show the highest corroded
and the least corroded sample in NaCl. The corrosion potential of 180- degree is higher than that of
30- degree, passivation occurring due to a coated Nickel substrate.
The stress effect and acidic solution accelerate the failure or fracture points because of increasing of
cracks propagation
Table of Contents
Cover Page i
Certification ii
Dedication iii
Acknowledgements iv
Table of Contents v
List of Tables viii
List of Figures x
Abstract xiii
Chapter one
1.0 Introduction…………………………………………………….
1.1The aim of research………………………………………………….
1.2 Objectives of the research…………………………………
1.3The scope of research………………………………………………
1.4 Expected contributions to knowledge ……………….
1.5 Justification………………………………………………………
Chapter two
2.0 Literature review…………………………………………….
2.1 Forms of corrosion………………………………………….
2.1.1 Uniform corrosion……………………………….
2.1.2Intergranular corrosion………………………
2.1.3Galvanic corrosion……………………………….
2.1.4Crevice corrosion………………………………….
6 | Page
2.1.5Pitting corrosion………………………………….
2.1.6Erosion corrosion………………………………….
2.1.7Stress corrosion cracking…………………….
2.1.8Selective leaching…………………………………
2.2Factors affecting corrosion…………………………….
2.2.1Temperature and velocity between the metal and the media…………...
2.2.2Surface finish and grain size…………………
2.2.3Stress and coating……………………………….
2.2.4Nature of the corrosion product………….
2.2.5 effect of oxygen…………………………………
2.2.6 Types of iron and steel…………………………
2.2.7 Influence of heat treatment……………….
2.3Fatigue
2.3.1Strain limitations……………………………….
2.3.2Residual stresses…………………………….......
2.3.3Thermal properties of steel…………………
2.4Surface treatments
2.4.1Electroplating……………………………………
2.4.2Electroless plating…………………………….
2.4.3Chemical process (chemical coating) ……
2.4.4Anodic oxidation process…………………….
2.4.5Hot dip coating……………………………………
2.4.6Vaccum plating………………………………….
2.4.7Plating……………………………………………….
2.4.8Thermal plating………………………………….
7 | Page
2.5Understanding the electroplating process
2.5.1 Electroless nickel…………………………….
Chapter three
3.0Materials and methods
3.1 Materials…………………………………………………….
3.1.1Equipment…………………………………………
3.2Methods
3.2.1Sample preparation………………………….
3.2.2Nickel electroplating………………………
3.2.2.1 Samples Pre-Treatment Operation
3.2.2.2 Electroplating Operation
3.2.3Materials and equipment used for nickel plating
3.2.4Procedures for plating low carbon steel…………………….
3.2.5Determination of the weight of nickel deposited on the low carbon steel
substrates…………………………….
3.2.6Preparation of corrosion media………………………………
3.2.7Experimental procedure………………………………………….
3.2.8Corrosion penetration rate (CPR) determination
Using weight loss…………………………………………………….
3.2.9Electrode potentials measurement………………………….
3.2.10Determination of corrosion rate by current
Densities measurement……………………………………………
3.2.11Surface micrographic examination……………………….
Chapter four
4.0Results and discussion
8 | Page
4.1 Coating analysis……………………………………………………………….
4.2Weight loss readings for the uncoated sample in NaCl………………
4.3 Weight loss readings for coated mild steel in NaCl………………
4.4Weight loss readings for the uncoated sample in H
2
SO
4
…………….
4.5Weight loss readings for the coated sample in H
2
SO
4
……………….
4.6Photo documentation after immersion………………………………
4.7 Discussion on potential readings in NaCl……………………………
4.8Discussion on potential readings in H
2
SO
4
………………………….
4.9Corrosion behavior of unprotected and protected
low carbon steel samples…………………………………………………
4.10 Microstructural analysis……………………………………………….
4.11Corrosion rate by current densities measurement…………….
Chapter five Conclusion……………………………………………………….
Chapter six Recommendation……………………………………………….
Chapter seven Reference………………………………………………………….
Appendix ……………………………………………………………………………….
9 | Page
LISTS OF TABLES
Pages
Table 2.1: Resulting Extreme Fiber Strains………………………………………………
Table 4.1: The chemical composition of the mild steel is showed below……………….
Table 4.2: Coated mild steel in NaCl …………………………………………………….
Table 4.3: Coated mild steel in
H
2
SO
4
……………………………………………………
Table 4.4: Weight loss reading for an uncoated sample of 30 degrees immersed in NaCl……
Table 4.5: Weight loss reading for an uncoated sample of 45 degrees immersed in NaCl……
Table 4.6: Weight loss reading for an uncoated sample of 60 degrees immersed in NaCl……
Table 4.7: Weight loss reading for an uncoated sample of 90 degrees immersed in NaCl……
Table 4.8: Weight loss reading for an uncoated sample of 180 degrees immersed in NaCl….
Table 4.9: Weight loss reading for a coated sample of 30 degrees immersed in NaCl………
Table 4.10: Weight loss reading for a coated sample of 45 degrees immersed in NaCl…….
Table 4.11: Weight loss reading for a coated sample of 60 degrees immersed in NaCl…….
Table 4.12: Weight loss reading for a coated sample of 90 degrees immersed in NaCl…….
Table 4.13: Weight loss reading for a coated sample of 180 degrees immersed in NaCl…….
Table 4.14: Weight loss reading for an uncoated sample of 30 degrees immersed in H
2
SO
4
…
Table 4.15: Weight loss reading for an uncoated sample of 45 degrees immersed in H
2
SO
4
…
Table 4.16: Weight loss reading for an uncoated sample of 60 degrees immersed in H
2
SO
4
…
Table 4.17: Weight loss reading for an uncoated sample of 90 degrees immersed in H
2
SO
4
…
10 | Page
Table 4.18: Weight loss reading for an uncoated sample of 180 degrees immersed in H
2
SO
4
…
Table 4.19: Weight loss reading for a coated sample of 30 degrees immersed in H
2
SO
4
……
Table 4.20: Weight loss reading for a coated sample of 45 degrees immersed in H
2
SO
4
……
Table 4.21: Weight loss reading for a coated sample of 60 degrees immersed in H
2
SO
4
…….
Table 4.22: Weight loss reading for a coated sample of 90 degrees immersed in H
2
SO
4
…….
Table 4.23: Weight loss reading for a coated sample of 180 degrees immersed in H
2
SO
4
……
Table 4.24: Results for Tafel plot………………………
11 | Page
LISTS OF FIGURES
Pages
Fig 2.1: Uniform attack of metal……………………………………………………….
Fig 2.2: Intergranular corrosion of metal……………………………………………….
Fig 2.3: galvanic corrosion……………………………………………………………...
Fig 2.4: Crevice corrosion of metal…………………………………………………….
Fig 2.5: Pitting corrosion of metal……………………………………………………….
Fig 2.6: Erosion corrosion of metal………………………………………………………
Fig 2.7: Stress corrosion crack…………………………………………………………….
Fig 2.8: Selective leaching of zinc…………………………………………………………
Fig 2.9: Residual Stress Distribution……………………………………………………….
Fig 2.10: Basic electrical circuit for electroplating…………………………………………
Fig 3.1: Schematic of the electroplating cell……………………………………………….
Fig 3.2 Before plating with Nickel coatings on Low Carbon steel of
angle 180
o
, 90
o
, 60
o
, 45
o
and 30
O
………………………………………………….
Fig 3.3 After plating with Nickel coatings on Low carbon steel of
angle 180
o
, 90
o
, 60
o
, 45
o
and 30
O
……………………………………………………
Fig 3.4: Experimental procedure…………………………………………………………….
Fig 3.5: Before immersion……………………………………………………………………
Fig 3.6: After immersion………………………………………………………………………
Fig 3.7: Schematic diagram for the determination of the current densities of nickel plated substrate
immersed in 0.5 M NaCl solution………………………………………….
12 | Page
Fig 4.1: Nickel plating angle 180
0
subjected to 0.5M NaCl for 15 days…………………….
Fig 4.2: Nickel plating angle 90
0
subjected to 0.5M NaCl for 15 days………………………
Fig 4.3: Nickel plating angle 60
0
subjected to 0.5M NaCl for 15 days………………………
Fig 4.4: Nickel plating angle 45
0
subjected to 0.5 M NaCl for 15 days……………………
Fig 4.5: Nickel plating angle 30
0
subjected to 0.5M NaCl for 15 days………………………
Fig 4.6: Un-plated steel Angle 180
0
subjected to 0.5 M NaCl for 15days……………………
Fig 4.7: Un-plated steel Angle 90
0
subjected to 0.5 M NaCl for 15days……………………
Fig 4.8: Un-plated steel Angle 60
0
subjected to 0.5 M NaCl for 15days……………………
Fig 4.9: Un-plated steel Angle 45
0
subjected to 0.5 M NaCl for 15days……………………
Fig 4.10: Un-plated steel Angle 60
0
subjected to 0.5 M NaCl for 15days………………….
Fig 4.11: plated steel Angle 60
0
subjected to 0.5 M in sulphuric acid for 15days………….
Fig 4.12a: Plot of Electrode Potentials against Exposure Time for Un-Plated
low carbon Steel Samples at various Plating Time, Immersed in NaCl………….
Fig 4.12b: Plot of Electrode Potentials against Exposure Time for Nickel Plated
low carbon Steel Samples at various Plating Time, Immersed in NaCl …………..
Fig 4.13a: Plot of Electrode Potentials against Exposure Time for Un-Plated low carbon
Steel Samples at various Plating Time, Immersed in H
2
SO
4
…………………....
Fig 4.13b: Plot of Electrode Potentials against Exposure Time for Nickel plated low carbon
13 | Page
Steel Samples at various Plating Time, Immersed in H
2
SO
4
…………………….
Fig 4.14a: Corrosion rate of the coupon in 0.5M NaCl solution of uncoated low carbon
steel………………………………………………………………………………
Fig 4.14b: Corrosion rate of the coupon in 0.5M NaCl solution of coated low carbon
steel………………………………………………………………………………
Fig 4.15: optical image of Angle 30………………………………………………………….
Fig 4.16: optical image of Angle 45………………………………………………………….
Fig 4.17: optical image of Angle 60………………………………………………………….
Fig 4.18: optical image of Angle 90………………………………………………………….
Fig4.19: optical image of Angle 180………………………………………………………….
Fig 4.20: comparison of corrosion density of coated sample 30 degree and
180 degree in NaCl environment…………………………………………………….
Fig 4.21: comparison of corrosion density of Uncoated sample 30 degree and
180 degree in NaCl environment……………………………………………………
