| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2000: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1999: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
QCM(Quartz Cristal Microbalance) and stainless steels covered with various ammount of sea salt, Ws, were put in the constant humidity chamber, and amount of absorbed water, W_<ab>(H2O), was measured. It was found that the ratio of (W_<ab>(H_2O)/Ws) was determined as a function of RH and was not depended on Ws, when Ws was more than 10^<-2> g/m^2 . This means that 1) the thickness of water film is proportional to Ws and 2) chemical conposition of waterfilm and conductivity are determined as functions of RH. The specific gravities and conductivities of the solutions with various content of sea salt were also measured. These values were considered to be equal to those of water films which had the same (W_<ab>(H_2O)/Ws) ratio, and resistance values between the anode and the defect under various Ws and RH conditions. It was found that the voltage needed to protect the defect was not so high ; the voltage was estimated to be 4.8V under the conditon with Ws=10^<-3>g/m^2 and RH=40%, under which the corrosivity was considered to be relatively mild.
A system to measure potential of Fe electrode and corrosion rate of it was developed. The potential and the corrosion rate were measured by Kelvin probe and QCM, respevtively, under various Ws, RH and potection current density conditions. Base on the measured resalts, the inner polarization curves were drawn. The protection potential and protection current density was determined to be - 750mV vs SCE and 20 μ A/cm^2 , respectively, where corrosion rate was less tan 0.1 μ, m/y, under the condition with RH=70%. These potential and current density values were not affected by RH.
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