The improvement mechanism of rust resistance of Nb and Cu containing ferritic stainless steels was studied from the view point of chemical compositions and stabilities of passivation films. Increase of Nb content up to 0.4% enlarges the passivation limit measured by the depassivation pH in Cl^- ions free solution and pitting potentials in Cl^- ions containing solution. Besides, Nb addition stablilizes the passivation film measured by the time for potential decay whether Cl^- ions are contained or not. Cu addition, however, has no influence on the passivation limit. It stabilizes the passivation film in Cl^- ions free solution, but deteriorates in Cl^- ions containing solution. Cu and Nb addition has no influence on the thickness of passivation film. Cr content in passivation film increases with increase of Nb content in the steel, but decreases with increase of Cu content. From these results, it was considered that the improvement of corrosion resistance by Nb addition is due to the increase of Cr content in passivation films.

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Corrosion characteristics of SiC, Si₃N₄, Al₂O₃, and ZrO₂ ceramics materials prepared by different sintering methods have been studied in high purity water at 200°-330°C, in 0.1kmol·m^-3 H₂SO₄ and 0.1kmol·m^-3 LiOH at 300°C for 50h. The mass, the reflection spectrum, the surface roughness, the IR spectrum, and the X-ray diffraction have been measured on each material before and after the corrosion tests in order to examine changes in the quality of the materials. It has been found that SiC had excellent corrosion resistance in all solutions at all temperatures tested. Si₃N₄ was seriously attacked by high purity water at 300°C, resulting thick powdered corrosion products on its surface. The attack was much severer in high purity water at 330°C and in 0.1kmol·m^-3 H₂SO₄ at 300°C. Al₂O₃ showed good corrosion resistance in high purity water up to 330°C. It was, however, seriously attacked in 0.1kmol·m^-3 H₂SO₄ and 0.1kmol·m^-3 LiOH at 300°C. The partially stabilized ZrO₂ was often suffered from serious cracking or breaking in all the solutions at 300°C. The transformation from the tetragonal phase to the monoclinic phase, which occured on it during corrosion tests, was thought to be one of the causes of the cracking or the breaking.

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UV photochemical decomposition of residual chlorine in tap water was studied as one of the feasible means to prevent pitting corrosion of copper tubes in central hot water supply systems. Nearly two years of long-term test was conducted by using the testing equipment simulating the conditions of actual systems that were installed in highstoried buildings. Three kinds of recirculating hot water loops were involved in the equipment. Two were supplied with the synthetic water with and without UV treatment throughout the test period. The rest was supplied with the untreated synthetic water until 531 days when replaced by the UV-treated. The 8 minutes of UV treatment by using a lowpressure type of mercury lamp could reduce the residual chlorine in the synthetic water from 10mg/l down to 0.2mg/l. The hot water was recirculating through each loop at the temperature of 60°C and at the flow rate of 0.3m/s. Throughout the test period, corrosion potential of copper tubes in each loop was monitored by using Ag/AgCl reference electrodes. Pitting corrosion propensity was evaluated by the periodical remove of the tubes from each loop, followed by the visual inspection and the extreme value statistical analysis. It was clearly shown that the decomposition of residual chlorine to the levels of less than 0.2mg/l could reduce the corrosion potential far below the pitting corrosion potential of 150mV (SCE), at around 100mV, and thereby preventing not only the initiation of pitting corrosion but also the growth of existing pits on copper tubes in the recirculating hot water loops.

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The influence of natural sea water on surface fatigue crack growth behavior of mild steel was investigated at four different testing frequencies, namely 0.33, 0.25, 0.17 and 0.09Hz in terms of the rate of crack growth and from the observation of the cross section and of the fractured surface of specimens. At 0.33Hz the correlation between the stress intensity factor range and the rate of crack growth followed Paris's law at the growth rate between 4×10^-7 and 1.5×10^-6mm/cycle in air and at the growth rate between 3×10^-7 and 1×10^-6mm/cycle in sea water. The rate of crack growth in sea water was found to be 1.6 times faster at the maximum than that in air within these ranges of growth rate. When testing at lower frequencies the rate of crack growth in sea water was found to be nearly equal to that at 0.33Hz at the early time of crack growth, but from a certain crack depth it slowed down with exposure time and finally stopped. This tendency for crack growth to decline in sea water increased with the decrease of frequencies. These phenomena can be explained by crack tip blunting by dissolution in sea water.

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Fracture mechanics has been used widely in various types of industries for flaw evaluation in design, inspection and maintenance procedure. In this text, the concept of fracture mechanics is reviewed especially for those who are not familiar with this type of approach for flaw evaluation. The text contains (1) Fundamental aspects of fracture mechanics (2) Development of codes and standards based upon fracture mechanics (3) Typical example of detected flaw evaluation and (4) future problem in flaw evaluation.

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Scanning tunneling microscope (STM) is becoming a popular technique to observe conducting solid surfaces with a resolution of -Å. The principle of this method is first described briefly. The experimental results presented here include atomic images of semiconductors and layered compounds and the topography of metal surfaces with nm resolution. STM can be used not only in vacuum but also in air or in soution. Several examples in this category are also presented. There are many attempts to observe insulating adsorbates such as DNA on conducting substrates. The principle and application of two of STM families, scanning tunneling spectroscopy (STS) and atomic force microscope (AFM), are described as well. Finally application of STM to ultramicro-processing is discussed.

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