Corrosion Inspection And Monitoring System For Ship’s Hull

ABSTRACT

This thesis presents a study on corrosion inspection and monitoring for a ship hull. The work discusses factors governing corrosion phenomena on the structural steel component level in ship hull. Different corrosion phenomena that may attack structural steel in contact with seawater are analyzed. Various forms of steel corrosion are described. The effect of steel composition and its variations on the corrosion development is discussed and its importance for corrosion is estimated. Methods and means for corrosion monitoring and inspection are analyzed and measures for corrosion prevention and control are discussed.

TABLE OF CONTENTS

 TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• PROBLEM STATEMENT
• AIM AND OBJECTIVE OF THE PROJECT
• RESEARCH QUESTIONS
• SIGNIFICANCE OF THE PROJECT

CHAPTER TWO

LITERATURE REVIEW

2.1     REVIEW OF THE STUDY

2.2     CORROSION PHENOMENA IN MARINE ENVIRONMENT

2.3 MARINE ENVIRONMENTAL AND OPERATIONAL FACTORS GOVERNING CORROSION

2.4    MARINE ENVIRONMENTAL FACTORS GOVERNING CORROSION OF STEEL STRUCTURAL ELEMENTS IN CONTACT WITH SEAWATER

2.5    MARINE ENVIRONMENTAL FACTORS GOVERNING ATMOSPHERIC CORROSION OF STEEL STRUCTURAL ELEMENTS

CHAPTER THREE

3.0      METHODOLOGY

3.1      CORROSION CONTROL MEASURES

3.2      CORROSION INSPECTIONS AND MONITORING

CHAPTER FOUR

• CORROSION HEALTH ASSESSMENT
• CHARACTERISTICS OF CH MONITORING SYSTEM
• MERITS OF DEVELOPING CH MONITORING SYSTEM
• ANTICORROSIVE PROTECTION FOR SHIPS HULL
• CONSIDERATIONS

CHAPTER FIVE

5.1      CONCLUSION AND RECOMMENDATION

REFERENCES

CHAPTER ONE

1.0                                                                INTRODUCTION

1.1                                                  BACKGROUND OF THE STUDY

Corrosion has become a problem of worldwide significance with much serious economic, health, safety, technological, and cultural consequences to our society. It is the main reason for the irreversible loose of metals and alloys. Most important are indirect costs related to failures of machines, equipment and facilities. Corrosion is one of the main reasons for deterioration of constructions and systems and for decreasing their safety, reliability and availability (Schumacher, 2019).

Ships and associated systems are constantly submitted to corrosive seawater and high humidity environments. Corrosion represents one of the most important phenomena leading to marine structures deterioration. Corrosion can cause rapid failure in marine systems, and there are many examples strewn through history.

Failure of a soldered joint in a seawater system caused the loss of the USS Thresher in 1963, killing all 129 men on board, and leaving the radioactive power unit on the floor of the Atlantic (Schumacher, 2019).

Failure of the propulsion system on the Braer oil Tanker due to seawater corrosion lead to it foundering on the Shetland Islands in 1993, spilling 100,000 tons of oil.

Sinking of Erica on 12 December 1999 lead to spillage of 19 800 tons of  heavy fuel oil near the coast of Brittany, France. The economic consequences of the incident have been felt across the region for many years.

These are just three of the largest and most damaging victims of marine corrosion, and improper anticorrosion design, there are many more failures every day. All these lead to downtime of marine systems, costing hundreds of thousands of Euros in lost revenue.

Effective measures counteracting the corrosion cannot be found without understanding its nature and without knowledge on factors influencing the corrosion rate.

Corrosion is a spontaneous process of degradation and destruction of materials caused by their interaction with the environment. Corrosion specifically refers to any process which involves the deterioration or degradation of metal components. The best known case is that of steel rusting. Corrosion is spontaneous and irreversible process because it is connected with a decrease in Gibbs free energy. Commonly used technical metals are not in pure state in the earth. They are in ores, under the form of chemical compounds which include sulphur, oxygen, carbon, hydrogen, etc. Minerals represent the thermodynamic  steady state of metals, in which the Gibbs free energy has a minimum value. Extraction of pure metals from their ores and their further processing requires energy, and this energy brings metals in thermodynamically less stable state. This is the reason which makes the metals to react with their environment and to return to the thermodynamically stable state they are predominantly found in nature, e.g. oxides. Metals which have a higher energy input in their production processes are more susceptible to corrosion, and have a lower electrode potential (Stratmann et al., 2010).

Most spread corrosion processes  are  electrochemical in nature, with a chemical reaction (mass- transfer) accompanied by the passage of an electrical current (flow of electrons and ions). This is due to the formation of a galvanic corrosion cell on the metal surface. Four elements must exist for galvanic cell formation and operation: corroding metal (or site)—anode, more noble metal (or site)—cathode, continuous conductive liquid path—electrolyte, and an oxidizing agent. Current flowing between anodic and cathodic sites is named corrosion current (I_corr) and it is a measure for the corrosion rate.

This work here discusses factors governing corrosion phenomena on the structural steel component level ship hull and methods and means for corrosion monitoring and inspection are analyzed and measures for corrosion prevention and control are discussed (Stratmann et al., 2010).

1.2     PROBLEM STATEMENT

Corrosion represents one of the largest through life cost component of ships. Ship owners and operators recognize that combating corrosion significantly impacts the vessels’ reliability, availability and through life costs. Mitigating unexpected corrosion can be very expensive in terms of direct cost and it also impacts heavily on platform availability. Corrosion can interfere with the operation of ship and impose increased loading stresses, accelerate deterioration of structure, and increases the hydrodynamic drag. Corrosion can cause the ship to fail prematurely resulting in loss of investment, safety and structural integrity. If a ship and its systems were designed with built-in corrosion resistance, this would result in less planned and unplanned maintenance and in substantial saving in through life costs. This study is carried out to discuss how corrosion can be inspected and monitored in a ship hull (Stratmann et al., 2010).

1.3      AIM AND OBJECTIVES OF THE STUDY

The main aim of the study is to carry out a study on the corrosion inspections and monitoring for ship hull. The objectives of this work are:

1. To review various inspections and monitoring systems management with respect to corrosion control of ship hull
2. To develop the concept of “Corrosion Health”, this would quantify the extent of corrosion at any point of steel ships’ operational life.

• To keep a ship hull in good condition

1.4      RESEARCH QUESTION

1. What is corrosion monitoring system?
2. How do you protect ship hull from corrosion?

• How are ships protected from corrosion?

1.5      SIGNIFICANCE OF THE STUDY

This study shall be used in determining the corrosion condition of ship structure, and to determine the effective of corrosion control systems. The advantage of this concept is in improving the platform availability and recommended values of Corrosion Health (CH).