Failure Mechanisms of Epoxy Coatings in Pipelines
Abstract
Epoxy, a thermosetting polymer due to its attractive properties, has been widely used in many industries as a coating material such as the oil and gas industries.
This study provides an insight into the corrosion behavior of epoxy looking at its adsorption properties at the epoxy steel interface and the adhesion behavior for different corrosion environments.
The study was carried out using conventional weight-loss measurements and microscopic observation after immersion in Hcl of varying pHs.
After 31days of exposure, the results indicate an increase in weight of the different coated steels implying that adsorption occurs in the epoxy.
Different mixing ratios of base to hardener were studied with different rates of adsorption obtained and the 2:1 ratio having the highest mass increase.
To test adhesion properties of epoxy on X65 low carbon steel hot water immersion test was adopted and the 3:1volume ratio recorded the highest weight gain.
High osmotic pressures result in causing vapor to migrate rapidly to the coating/steel interface at areas of marginal coating adhesion.
This weakens the polar bond formed between the coating and the steel surface and may crack due to hydrostatic stresses, exposing the steel to corrosive environments or may start corroding the steel underneath leading to the deterioration of the pipeline.
Table Of Contents
Dedication………………………….. iii
Acknowledgement………………………………….. iv
Abstract………………………………………. v
Table of Contents……………………………. vi – viii
List of Figures………………………….. ix-x
List of Tables…………………………… xi
CHAPTER ONE: INTRODUCTION
- Background……………………………… 1
- Problem statement……………………………… 3
- Study objective………………………………………… 4
Reference…………………………… 5
CHAPTER TWO: LITERATURE REVIEW
- Basic Concepts of Corrosion………………………………. 6
- Epoxy…………………………………………………… 7
- Components of epoxy……………………………………… 7
- Epoxy equivalent weight…………………………………… 9
- Corrosion………………………………………….. 10
- Mechanism of corrosion………………………………….. 11
- Theories of Moisture Absorption in an Epoxy Resin…………………….. 20
- Prior work………………………………… 23
Reference………………………… 24
CHAPTER THREE: MATERIALS AND METHODS
- Materials……………………………………. 27
- Epoxy Components…………………………….. 27
- X65 Steel…………………………………………… 27
- Sample Preparation………………………………….. 28
- Mixing of epoxy……………………………………. 28
- Preparation of the Steel Surface…………………………. 28
- The Coating Process…………………………….. 29
- Preparation of the Solution………………………… 29
- Experiment 1………………………………………… 31
- Water Absorption Test……………………………………. 31
- Experiment 2…………………………………….. 32
- Hot Water Immersion Adhesion Test……………………… 32
- Metallurgraphic Sample Preparation………………… 32
- Optical Microscopy characterization………… 33
CHAPTER FOUR: RESULTS AND DISCUSSION
- Experiment 1: Moisture Absorption……………….. 34
- Experiment 2;Hot water Adhesion Test……………………….. 39
- General discussion……………………………………… 48
- Control Experiment 3………………………… 49
- Surface Morphology……………………………….. 51
- Optical Micrographs………………………………… 51
Reference…………………………………. 52
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION
- Summary………………………………. 53
- Conclusion………………………………. 53
- Suggestion for Future Work………………. 54
Introduction
Background Of Study
Pipelines are a safe and efficient means of high volume transportation of oil and gas. They are expected to resist the damaging effects of the surrounding environment and the potential damage from the material that is being conveyed might cause.
Corrosion is an important form of pipeline deterioration due to aggressive environments. Buried pipes are located with continuously changing environmental conditions which may lead to corrosive environment [5].
Various coatings, paints or cathodic protections are usually used to protect pipes against the effect of external corrosion. Corrosion may become a serious problem as the pipeline ages.
Metal corrosion can be controlled by using two techniques: 1) Passive protection and 2) Active protection or cathodic protection.
Passive protection involves an electrolytic separation between the metal and the pipeline environment, through application of appropriate coatings.
Coatings provide an effective method used for the protection of pipelines against corrosion. They provide a physical corrosion barrier between the steel structure and the surrounding environment.
References
Rajput, K. 2006, Material Science and Engineering,S. K. Kataria & Sons, Nai –Saraki, Delhi.854 -872
http://www.wisegeek.com/what-is-corrosion.htm
Budinski, K. G. and Budinski, M. K, 1986, Engineering Materials, Properties and Selection, Ninth Edition, Pearson Prentice Hall, Upper Saddle River, New Jersery, Columbus, Ohio. 133 – 166
Mars Fontana 1986, Corrosion Engineering, Third Edition, McGraw-Hill Book Company,.ISBN 0-07-100360-6. 1 –277, 300 -444]
Xianmingshi,Tuan, Effect of nanoparticles on the anticorrosion and mechanical properties of epoxy