This project covers a study of the effect of seawater corrosion on 0.34% and 0.36% carbon steel
compositions.
Two (2) specimens (steel rods) of length 150mm (each) for both steel compositions were
obtained. Out of each was gotten four (4) specimens of 10mm length, 10mm diameter and two
(2) specimens of 50mm length, 10mm diameter. This yielded a total of twelve (12) samples. For
each steel composition, one (1) specimen of 10mm length and one (1) specimen of 50mm length
were heat treated. The heat treated specimen of 10mm length and one corresponding sample that
was not heat treated for each steel composition were exposed to seawater for seawater corrosion
process. The heat treated specimen of 50mm length and one corresponding sample that was not
heat treated for each steel composition were used for the micrography section of the project.
The result showed that the corrosion rate of 0.34%C changed from 0.21633mmpy to
0.15711mmpy on exposure to seawater. It also shows that the corrosion rate of 0.36%C changed
from 0.17889mmpy to 0.00024519mmpy on exposure to the same seawater condition. The
reason for these changes in values of corrosion rates while exposed to the same environment
constitutes the core of this project.
TABLE OF CONTENT
-ABSTRACT ---------------------------------------------------------------------------------------13
CHAPTER ONE ---------------------------------------------------------------------------------------14
INTRODUCTION ---------------------------------------------------------------------------------------14
1.1 Background ---------------------------------------------------------------------------------------14
1.2 Statement of problem ------------------------------------------------------------------------------15
1.3 Aim of study ---------------------------------------------------------------------------------------16
1.4 Objective of the study ------------------------------------------------------------------------------16
1.5 Scope of work ---------------------------------------------------------------------------------------16
CHAPTER TWO ---------------------------------------------------------------------------------------17
LITERATURE REVIEW ------------------------------------------------------------------------------17
2.1 Medium carbon steels ------------------------------------------------------------------------------17
2.2 Heat treatment ---------------------------------------------------------------------------------------17
6 2.3 Types of heat treatment of steel ------------------------------------------------------------20
2.3.1 Annealing ---------------------------------------------------------------------------------------20
2.3.2 Normalising ---------------------------------------------------------------------------------------20
2.3.3 Spheroidising ---------------------------------------------------------------------------------------20
2.3.4 Case Hardening ------------------------------------------------------------------------------21
2.3.5 Hardening ---------------------------------------------------------------------------------------22
2.3.6 Tempering ---------------------------------------------------------------------------------------22
2.4 Corrosion ---------------------------------------------------------------------------------------23
2.4.1 The consequences of corrosion ------------------------------------------------------------24
2.4.2 Chemistry of corrosion ---------------------------------------------------------------------25
2.4.3 Types of corrosion ------------------------------------------------------------------------------26
2.4.4 Measurement of corrosion ---------------------------------------------------------------------27
CHAPTER THREE ---------------------------------------------------------------------------------------30
MATERIALS AND METHODOLOGY ------------------------------------------------------------30
3.1 Materials ---------------------------------------------------------------------------------------30
3.2 Methodology ---------------------------------------------------------------------------------------32
3.2.1 Cutting and unribbing ------------------------------------------------------------------------------32
3.2.2 Heat treatment ------------------------------------------------------------------------------32
3.2.3 Exposure to sea water ------------------------------------------------------------------------------33
3.2.4 Microstructure ---------------------------------------------------------------------------------------33
CHAPTER FOUR ---------------------------------------------------------------------------------------34
RESULTS AND DISCUSSION ---------------------------------------------------------------------34
4.1 Results ------------------------------------------------------------------------------------------------34
4.2 Discussion ---------------------------------------------------------------------------------------36
4.2.1 The effect of seawater corrosion on 0.34% medium carbon steel ------------------------36
7 4.2.2 The effect of seawater corrosion on 0.36% medium carbon steel ------------------------36
4.2.3 The effect of seawater corrosion on 0.34% and 0.36% medium carbon steel (the comparison) ------------------------------------------------------------------------------------------------36
CHAPTER FIVE ---------------------------------------------------------------------------------------37
CONCLUSION AND RECOMMENDATION ---------------------------------------------------37
5.1 Conclusion ---------------------------------------------------------------------------------------37
5.2 Recommendation ------------------------------------------------------------------------------37
REFERENCES ---------------------------------------------------------------------------------------38
APPENDIX 1 ------------------------------------------------------------------------------------------------40
APPENDIX 2 ------------------------------------------------------------------------------------------------41
