Experiments have been carried out on 1T-CT and 1T-WOL crack growth specimens of mill annealed SUS 316L (Type 316L) stainless steel to examine the IGSCC susceptibility of non sensitized stainless steel in 288°C water. SUS 316L stainless steel was mill annealed at 1100°C for 10min. Intergranular crack growth was detected on the SUS 316L stainless steel specimen in water containing 0.2ppm O2 and conductivity of 0.5μS/cm, and the crack growth rate of this material was about a factor of 10 lower than that of a sensitized SUS 304 stainless steel. Crack growth was not detected, however, on the specimen tested in 0.1μS/cm conductivity water. Intergranular attack was also found out in creviced region of SUS 316L specimen in 0.5μS/cm conductivity water, and clear intergranular morphology was observed by scanning electron microscopy after Streicher test. On the other hand, intergranular attack in creviced region and intergranular morphology after Streicher test were not taken on mill annealed SUS 304L stainless steel. Molybdenum included in SUS 316L stainless steel seemed to play a rule in acceleration of intergranular corrosion in relatively high conductivity water condition.
Titanium nitride has been used as corrosion-resistant films in recent years. In this investigation, the effect of nitrogen content of titanium nitrides on the corrosion resistance in H2SO4 was examined. Titanium nitride powders having various compositions were synthesized by the reaction of titanium hydride with nitrogen gas and used as specimens. X-ray diffraction showed that the nitrides of 17.5-29.0at% N had the mixed structure of α-Ti and Ti2N, those of 33.6-37.5at% N the mixed structure of Ti2N and TiN, and those of 40.5-48.9at% N the single phase of TiN. The relationship between the lattice parameter “a” of TiN and the nitrogen content was expressed as the equation a(nm)=1.74×10-4·N(at%)+0.4153. The change in the amount of dissolved titanium from the powders with time in 1kmol·m-3 H2SO4 at 373K fitted to the equation 1-(1-R)1/3=k·t, where R was the weight loss ratio of titanium. The rate constant k decreased with increasing nitrogen content and corrosion was apparently inhibited when the nitrogen content of titanium nitrides was more than 40at%. On specimens with nitrogen content less than 40at%, corrosion occured preferentially on Ti2N in the mixed structure.
The effect of oxidation conditions on metal release of Type 439 and Mod. 409 ferritic stainless steels in deaerated pure water at 488K was investigated. The behavior of metal release was also discussed in relation to the surface films which were formed by various oxidation conditions. The results obtained are as follows: (1) The oxidation treatments in the atmosphere of low oxygen potential such as high purity argon gas and high vacuum condition at 1123K for short time were effective to decrease the metal dissolution, and the oxide films primarily consisted of double oxide layer consisted of Ti2O3 in outer and MnCr2O4 in inner layer. (2) Titanium concentration into surface oxide film was increased in proportion to the logarithm of heating time at 1123K. (3) It could be obtained that a small quantity of titanium addition to high purity ferritic stainless steels was effective to decrease the metal dissolution through the formation of thin titanium oxide film, together with the suppression of the sensitization, by heat-treated in the atmosphere of low oxygen potential.
Scanning vibrating electrode technique (SVET) system was applied to measure corrosion current density profiles around Pt foil embedded in epoxy resin except its edge, which was used to simulate intergranular corrosion. The system was calibrated under the condition of uniform current. Output voltage, V, became larger with decreasing conductivity of the test solution, κ, and increasing vibrating amplitude of sensor probe, a. Measuring sensitivity did not depend on frequency of vibration, f, under the condition of uniform current. Laplace equation could be applied for corrosion current distributions around foil-shape electrode with width of t. When height of sensor probe from the specimen surface, h, could be decreased down to h≤t/2, condition A, corrosion current distribution could be considered to be uniform and net corrosion current density, i0, could be determined as i0=πip/2, where ip was the corrosion current density just above the center of the electrode. When h was larger than t/2, condition B, corrosion current flowed out in all directions from the electrode and identification sensitivity of ip=ti0/πh became better with decreasing h. Corrosion current profiles around Pt foil electrode were measured under various conditions of f, h and width of Pt foil, t. Measuring sensitivity became improved with increasing f and then leveled off after a f-value of 300Hz. Because V was unstable under the conditions with f=50n(Hz) (n=7, 8, 9…) under the influence of AC power source (f=50Hz), f=370Hz was adopted in this work. Relationship between ip and h satisfied the Laplace equation under condition B. With regard to corrosion current flowing out from two Pt foils at the distance of d, h was required to be less than d/2 to detect two peaks of corrosion current and to determine the positions of Pt foils. These strong dependency on h of the measured intergranular corrosion current profiles are attributed to the adopted conditions which remains within condition B.
Quartz crystal microbalance (QCM) and surface acoustic wave (SAW) techniques, which are capable of detecting a trace amount of weight changes in the magnitude of 10-9g·cm-2 from the changes of resonant frequency, are useful for monitoring a trace of corrosion of metal thin films. This article dealt with application of QCM and SAW to atmospheric corrosion and aqueous corrosion of metal thin films. Adsorption of water molecules, corrosion kinetics and corrosion mechanism of metal thin films were discussed on the basis of typical results obtained by QCM and SAW. Furthermore, it was shown that stress was one of predominant factors influencing the resonant frequency of QCM in the case of absorption of hydrogen or deuterium atoms into Pd thin film.
A review of the investigations on “Cold Fusion” is given. A brief history of developments of cold fusion researches is described. Representatives of excess heat generation, tritium production and neutron emmission in mainly electrolysis of D2O, i. e., Fleischmann-Pons experiments, are involved. Other experimental results suggesting the occurrence of a fusion reaction and the models proposed to account for the observations are also given.