A corrosion cost survey in Japan in FY 2015 was conducted, and compared with those conducted in 1974 and 1997. Surveys in three economic situations （growing period: 1974, transition period: 1997, mature stage: 2015） are the first attempts in the world. The total amount of corrosion cost by Uhlig method in this survey （2015） was 4.3 trillion yen, or 0.78％ of GNI. This total amount was 0.94 or 1.68 times of that in FY1997 （4.6 trillion yen） or in FY1974 （2.5 trillion yen）. The result that the total amounts in FY2015 and in FY1997 are almost same is considered to indicate the direct corrosion control costs in the mature stage of economic conditions which are 0.7～0.8％ of GNI. The total amount of corrosion cost by Hoar method was 6.6 trillion yen, or 1.27％ of GNI. This total amount was 1.27 or 6.22 times of that in FY1997 （5.2 trillion yen） or in FY1974 （1.1 trillion yen）. In the Hoar method, the maintenance costs are also integrated, while in the Uhlig method, the initial costs are mainly integrated. The Hoar/Uhlig-ratio increased a little from 1.13 （FY1997） to 1.53 （FY2015）. It indicates that the maintenance is considered to be more important. “Corrosion Cost Performance” increased from previous survey （1997） to this survey （2015） by using “New Technologies”, while the total amount of “Cost of Corrosion” in 2015 is almost same to that in 1997. New Technologies-monitoring, simulation, data base, AI, Risk Based Maintenance, etc. ―are effective to increase “Anti-Corrosion Level” and to decrease “Cost of Corrosion”.
An electrochemical surface treatment technique to improve the localized corrosion resistance of zirconium in chloride ion environment has been developed. The combination of anodic and cathodic polarization cycles was applied to induce selective dissolution of the inclusions that initiated localized corrosion on zirconium. Shallow-shaped traces were observed on the specimen surface after the treatment, indicating the dissolution of the inclusions. The treatment with constant anodic current and constant cathodic potential in a concentrated phosphate-buffered saline resulted in the high pitting potential over 2 V in a physiological saline. Thus, the localized corrosion resistance of the treated Zr was significantly improved by this technique.
We often experienced that crevice corrosion behavior on initiation and propagation changed among the tests if the test condition were the same in the crevice corrosion test. This paper makes clear the variation of the initiation site properties: position, number, time orders and initiation time, and the propagation behavior of the crevice corrosion after 600 s from the initiation among 16 times tests. The crevice corrosion tests of SUS304 stainless steel were carried out on the same test condition for 16 times in artificial seawater under the constant potential of 499 mV （SHE）. We confirmed that the initiation site properties were very different in the test chances. The first initiation of crevice corrosion tends to occur at the near site of crevice mouth. The second initiation site was not influenced by the position of the first initiation. The crevice corrosion initiation time near the crevice mouth tends to be shorter than that occurred in the inner part of crevice. It was not influenced by the order of initiation. The crevice corrosion areas after 600 s from the first initiation time were changed from 0.015 to 0.110 cm2. The propagation rate of crevice corrosion area was influenced by the potential distribution that was depended on the IR drop from the crevice mouth. The propagation rate of the crevice corrosion near the crevice mouth tended to be faster than that occurred in the inner part of crevice.