by Ku, Nim Chung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references. / by Ku, Nim Chung. / Acknowledgment --- p.i / Abstract --- p.ii / Table of contents --- p.iv / List of figures --- p.viii / List of tables --- p.xiv / Chapter Chapter One --- Introduction / Chapter 1.1 --- History of permanent magnet materials --- p.1 / Chapter 1.2 --- NdFeB intermetallic compound --- p.4 / References --- p.8 / Chapter Chapter Two --- Background / Chapter 2.1 --- Corrosion and corrosion control --- p.9 / Chapter 2.1.1 --- Electrochemical mechanisms --- p.10 / Chapter 2.1.2 --- Types of corrosion cell --- p.12 / Chapter 2.1.3 --- Types of corrosion --- p.14 / Chapter 2.1.4 --- Corrosion control --- p.15 / Chapter 2.2 --- Intermetallic compounds and phases --- p.19 / References --- p.26 / Chapter Chapter Three --- Instrumentation / Chapter 3.1 --- Introduction --- p.27 / Chapter 3.2 --- Vacuum evaporator --- p.28 / Chapter 3.3 --- Vacuum furnace --- p.29 / Chapter 3.4 --- Scanning electron microscopy (SEM) & Energy dispersive analysis (EDX) --- p.29 / Chapter 3.5 --- Corrosion chamber --- p.31 / Chapter 3.6 --- Vibrating sample magnetometer (VSM) --- p.31 / References --- p.43 / Chapter Chapter Four --- Moisture corrosion test on a bare NdFeB permanent magnet (without any coating) / Chapter 4.1 --- Introduction --- p.44 / Chapter 4.2 --- Experimental procedures --- p.45 / Chapter 4.3 --- Results from visual inspection --- p.45 / Chapter 4.4 --- Corrosion behavior --- p.46 / Chapter 4.5 --- Measurement of the saturated magnetization --- p.47 / Chapter 4.6 --- The effect of corrosion on the magnetic property of the NdFeB magnet --- p.48 / Chapter 4.7 --- Conclusions --- p.49 / References --- p.57 / Chapter Chapter Five --- Interfacial reaction between the A1 coating and the NdFeB magnet / Chapter 5.1 --- Introduction --- p.58 / Chapter 5.2 --- Experiments --- p.59 / Chapter 5.3 --- The Interaction between the A1 coating and Magnet --- p.60 / Chapter 5.4 --- Conclusions --- p.63 / References --- p.67 / Chapter Chapter Six --- Corrosion behavior of A1 coated NdFeB magnet in moist environment / Chapter 6.1 --- Introduction --- p.68 / Chapter 6.2 --- Experiments --- p.69 / Chapter 6.3 --- Results --- p.69 / Chapter 6.3.1 --- The annealed samples before corrosion test --- p.70 / Chapter 6.3.2 --- Microstructure changes after 3 days of corrosion --- p.70 / Chapter 6.3.3 --- Corrosion process in the annealed samples --- p.71 / Chapter 6.4 --- Corrosion behavior --- p.73 / Chapter 6.4.1 --- Effects of NaCl on the samples --- p.73 / Chapter 6.4.2 --- Effects of the inter-diffusion --- p.74 / Chapter 6.5 --- Conclusions --- p.75 / References --- p.79 / Chapter Chapter Seven --- Dual layer coating of either Ti/Al or Ni/Al on the NdFeB permanent magnet / Chapter 7.1 --- Introduction --- p.80 / Chapter 7.2 --- Experiments --- p.81 / Chapter 7.3 --- The Interaction between the A1 and Magnet --- p.81 / Chapter 7.3.1. --- The Ti/Al coated magnets --- p.82 / Chapter 7.3.2. --- The Ni/Al coated magnets --- p.83 / Chapter 7.4 --- Volume contraction of the intermetallic coatings --- p.84 / Chapter 7.5 --- Conclusions --- p.85 / References --- p.90 / Chapter Chapter Eight --- Conclusions and suggestions for further studies --- p.91