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A new method to estimate the degree of a corrosion attack on silver taking into account seasonal variations of temperature and relative humidity was developed in order to evaluate the corrosivity of an atmospheric environment. In addition to measuring the thickness of corrosion product on silver using a resistance-type corrosion sensor, temperature and relative humidity were measured in a machine room for a certain period. Based on these measured data, we investigated a method to estimate the thickness of corrosion product on silver that forms in one year. First, the temperature in the machine room was estimated for a one-year period by adding the seasonal component of temperature at the nearest monitoring site of the Japan Meteorological Agency (JMA), the difference in temperature between the machine room and the JMA site, and the irregular component of temperature in the machine room. The relative humidity was estimated by substituting the estimated temperature in the machine room and the absolute humidity at the JMA site into the Sonntag formula. Second, a corrosion gas coefficient was determined by using the thickness of corrosion product on silver and the temperature and relative humidity in the machine room for the measurement period. Third, the thickness of corrosion product on silver for a unit period was calculated by substituting the corrosion gas coefficient and the estimated temperature and estimated relative humidity for a unit period into the already proposed estimation equation of silver corrosion under a constant environment. The thickness of corrosion product on silver for a yearly period can be estimated by accumulating the thickness of corrosion product on silver for the unit period. With a preferable measurement period of three months, except for the winter season, the yearly thickness of corrosion product on silver can be estimated within a 10 percent margin of error.

The mechanical reliability of sensing glass fiber is one of the important problems in the practical use of fiber-optic sensors. To ensure long-term reliability on a mass-production level, a method of proof-testing is applied to a sensing glass fiber that will be subjected to mechanical deformation in its service situation. We propose to employ a higher strain level (screening level) in the proof-testing with a fiber-recoating technique that can suppress excessive damage during the testing. We consider a standard lifetime of 15 years of automotive applications and ensure a practical level of failure probability by a model calculation by using the strength data of a prototype fiber with the method of fracture-mechanics theory.

JIS K6234 4) 2) 2 2 1 3 EPDM (Ethylene Propylene Diene Monomer rubber) 4.3 5.8mm EPDM-A EPDM-B EPDM-C φ15mm 99.9% 1mm φ15mm SiC #1000 Estimation of Emission Characteristics of Sulfur Gas from Rubber by Rintaro MINAMITANI Silver, a typical material used in electronic devices, corrodes in sulfur gas emitted from rubber. To evaluate this corrosion damage of silver, we have established a new method for estimating the two emission characteristics of sulfur gas from rubber : initial sulfur-emission concentration and decrease rate of emission. Firstly, we used a long-term silver-corrosion test with rubber at 70−30 to investigate the emission mechanism and emission characteristics of sulfur gas from free sulfur, i.e., non-linked sulfur, in rubber. This investigation showed that the free sulfur in rubber is consumed by crosslink reaction between rubber chains and by sulfur-gas emission. The sulfur-consumption rate is controlled by the crosslink reaction at 70−50 , while it is controlled by sulfur-gas emission at 30. The emission characteristics at the temperature that the sulfur-consumption rate is controlled by sulfur-gas emission (i.e., 30) can be estimated by corrosion analysis considering sulfur-gas diffusion and the corrosion reaction of sulfur gas on silver. Secondly, we investigated the relationship between the amount of free sulfur and the emission characteristics. This investigation found that the amount of free sulfur can be calculated by integrating concentration of sulfur-gas emission. Given that result, we were able to establish a new method for estimating emission characteristics from the amount of free sulfur by chemical analysis and the initial concentration of sulfur-gas emission by a short-term silver-corrosion test with rubber.

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