Thesis Abstract

Abstract
Cathodic protection is a crucial method for preventing corrosion in metal structures, especially in harsh environments such as marine environments or underground pipelines. This research project focuses on the design and installation of a cathodic protection system using zinc anodes. Zinc is a widely used sacrificial anode material due to its high electrochemical potential and cost-effectiveness. The project begins with a detailed examination of the principles of cathodic protection and the electrochemical reactions involved in the corrosion process. The research delves into the factors influencing the selection of zinc anodes, including the type of structure, coating efficiency, and current requirements. The design phase involves determining the number and placement of zinc anodes to ensure uniform protection across the metal surface. The installation process is a critical aspect of the project, involving the proper positioning and securing of the zinc anodes to the structure. Special attention is paid to ensuring good electrical contact between the anodes and the metal surface to facilitate the flow of protective current. The project also includes the installation of monitoring equipment to regularly assess the effectiveness of the cathodic protection system. The effectiveness of the cathodic protection system is evaluated through a series of tests and measurements, including potential measurements, current density measurements, and visual inspections of the protected structure. The research project aims to demonstrate the ability of the zinc anodes to provide long-term corrosion protection for the metal structure in various environmental conditions. Overall, the design and installation of a cathodic protection system using zinc anodes require careful planning, attention to detail, and adherence to industry standards and best practices. By implementing an effective cathodic protection system, metal structures can benefit from extended service life and reduced maintenance costs. This research project contributes to the field of mechanical engineering by offering practical insights into the design and implementation of cathodic protection systems using zinc anodes.

Thesis Overview

INTRODUCTION

1.1 Background of study

Cathodic protection (CP) is a method of controlling corrosion or a means of preventing corrosion of metal and can be applied to any buried and/or submerged metallic structures. It is normally used in conjunction with coatings and can be considered as a secondary corrosion control technique.

Cathodic protection can, in principle, be applied to any metallic structure in contact salty media (electrolyte). In practice its main use is to protect steel structures buried in soil or immersed in water. Structures commonly protected, includes:

    Cross country pipelines

    Exterior surfaces of pipelines immersed in water

    In plant piping

    Above ground storage tank bases

    Buried tanks and vessels

    Internal surfaces of tanks, vessels, condensers and pipes

    Well casings

    Foundation piling, steel sheet-piling

    Piling – tubular, sheet steel and foundation

    Marine structures including jetties, wharfs, harbours, piers

    Ships, hulls

    offshore platforms

    Reinforcing steel in concrete

Corrosion is a very serious problem. Three areas in which corrosion are important are in economic, improved safety and conservation of resources. The leakage of hazardous materials from a transport pipeline represents not only the loss of natural resources but also the potential for serious and dangerous environmental impact, and human fatalities. While pipelines are designed and constructed to maintain their integrity, diverse factors (e.g., corrosion) make it difficult to avoid the occurrence of leakage in a pipeline system during its lifetime.

All metals needs energy to be transformed from their oxide (natural) state to a refined state. The process of taking this energy away from the metal is called corrosion. Metals tend to revert back to their natural state when reacting with the environment. This corrosion reaction that occurs is an oxidation-reduction reaction. The purpose of cathodic protection is to stop this corrosive process.

Cathodic protection is the most important of all approaches to corrosion control techniques. One of the types of cathodic protection is sacrificial anode or galvanic cathodic protection. Corrosion occurs through the loss of the metal ions at anodic area to the electrolyte. Cathodic areas are protected from corrosion because of the deposition of hydrogen or other ions that carry current (Sandoval, A., et.al 2001). By using the sacrificial anode technique, the steel pipe will be protected from corrosion but the other metal which is the anode will corrode. In designing this method we must analyze parameters such as factor affecting corrosion, the amount of anode and rate of corrosion, the current densities and the total resistance.

Corrosion is an electrochemical process in which a current leaves a structure at the anode site, passes through an electrolyte, and reenters the structure at the cathode site. Differences in potential at different points along the pipe begin to develop. For example, because it is in a soil with low resistivity compared to the rest of the line, current would leave the pipeline at that anode site, pass through the soil, and reenter the pipeline at a cathode site. These potentials generate corrosion currents which leave the pipe to enter the soil at certain selective locations