One of the methods to monitor metal corrosion behavior in the atmosphere as a mass change of the ng/cm2 order continually is the quartz crystal microbalance（QCM）method. The corrosion rates of multiple metals were simultaneously monitored with the multi-channel QCM sensors, and the concentration of corrosive gases were studied by the QCM measurement based on the inverse estimation method. The relationship between the corrosion rates and the environmental factors was formulated by considering the corrosion rates of silver, cobalt, and copper as the function of SO2, NO2, H2S and relative humidity. And the inverse estimation of the concentrations of corrosive gases can be derived from the basis of these approximate equations. Moreover, in order to evaluate the atmospheric corrosivity in an electrical control unit room in a steelmaking plant, the temperature, the relative humidity and corrosion rates of metals on QCM sensors were monitored. The temperature, the relative humidity, and the corrosion rates in a given day were distributed according to the normal probability law. The concentrations of H2S, SO2 and NO2 were estimated from the mean values of the relative humidity and the corrosion rates. The gas concentrations thus obtained by this method were roughly close to those analyzed by conventional measurement methods. The atmospheric corrosivity will be able to estimate based on the monitoring of the corrosion rates with multi-channel QCM sensors.
We investigated retrofit design in cathodic protection（CP）with galvanic anodes made from an aluminum alloy. In conventional retrofit design, the decrease in CP current reduction（which affects the life of anodes）is estimated based on nominal durability values. The current reduction rate falls to a level far below the design value, leading to an increased number of facilities in which the anode life exceeds the design service life. As this trend is due to exaggerated design, it is necessary to review retrofitting methods in order to enable more effective and economical maintenance. After detailed analysis and discussion, we developed an innovative methodology for an optimized maintenance system in galvanic anode CP. To test the assumptions made, we conducted on-site, shortterm testing with an actual structure and confirmed the validity of the new design methodology. The method, which takes current reduction into consideration, allowed more accurate prediction of anode life and a reduction in the initial costs of CP facilities.
Reduction mechanism of nitrate ion on titanium electrode was investigated using electrochemical method. Cathodic polarization curve of titanium was measured in nitric acid with different concentrations of ions （H＋，NO3－，HNO2）. Reduction mechanism of nitrate ion on titanium was investigated from Tafel slope and reaction order of each ions. It was considered that reduction of titanium oxide was involved in reduction mechanism of nitrate ion on titanium, and reduction mechanism was suggested as follows. NO3－ ⇄ NO3ad－ （QE） TiO2 + H+ + e－ ⇄ TiOOH （QE） NO3ad－ + TiOOH → (NO3－－TiOOH)ad （RDS） (NO3－ － TiOOH)ad + H+ + e－ → NO2ad－ + TiO2 + H2O