Surface stress and surface tension are important parameters for surface energetics of metal electrode. At first, the difference and relation between surface stress and surface tension were explained briefly and then, the bending beam method (BBM) was introduced as a powerful tool for measurement of the changes in surface stress of metal electrode in aqueous solution. The results of changes in surface stress obtained by BBM for the Pt and Au electrode surfaces oriented mainly to the (111) plane were exampled and discussed from the viewpoint of surface energetics. The surface stress of the Pt (111) electrode changed to the compressive direction during OH adsorption prior to the formation of PtOH monolayer. Particularly, the derivative of surface stress with electrode potential took a maximum, which was explained by the increase in compressive surface elastic strain due to strong bond of adsorbed OH with substrate Pt atom, inducing the surface charge density resulted in the major contribution to the maximum. The similar behavior of the change in surface stress for the Au (111) electrode in aqueous solution containing iodide ions was observed during iodine adsorption prior to the formation of AuI monolayer and was explained by the same manner as those of the Pt electrode. Moreover, the two dimensional isothermal compressibility of the iodine adlayer or the underpotentially deposited Pb monolayer on Au (111) electrode was evaluated by connecting the changes in compressive surface stress with the changes in the nearest neighbor distance between adatoms obtained from surface X-ray scattering.
Whole life costing (WLC) is probably the best tool available, provided that the input is sensible and the output tempered with engineering judgment. However, in general, there appeared to be a lack of information about the cost of maintenance and shutdown activities. Therefore, it is necessary to obtain data of the type needed to allow the application of WLC. In the present worth method, costs are discounted to the present point in time at a reasonable rate of return that is generally the discount rate. WLC of a port structure concerns the costs of construction, maintenance, shutdown and demolition. The cost of shutdown can be many times higher than the engineering costs of maintenance work. The discount rate and the cost of shutdown are dominant factors in the economic appraisal of port structures. In this paper, in accordance with the PIANC WG31 report, data for WLC, the discount rate, and the costs of shutdown and maintenance are considered, and an example of life cycle management (LCM) in the port of Kamsar (Guinea) is shown.
In order to clarify the effect of microstructure on CO2 corrosion resistance of carbon and low Cr steels (Cr content of 1 to 5 mass %), immersion tests were carried out in CO2 environment at 60 or 80°C by using carbon and low Cr steels with different microstructures. The relationship among corrosion behavior, microstructure and corrosion products structure were investigated. For carbon steel, ferritic pearlitic microstructure had better localized corrosion resistance than martensitic microstructure, because lamellar Fe3C improved denseness and adhesion of the primary corrosion product. On the other hand, for low Cr steel, martensitic microstructure had better CO2 corrosion resistance than ferritic pearlitic microstructure. From the result, the primary corrosion product with good corrosion resistance is considered to be formed on homogeneous microstructure for low Cr steel. Weight loss of the martensitic steels with more than 3%Cr was as low as one forth of carbon steel with ferritic pearlitic microstructure. The primary corrosion product formed on 3%Cr martensitic steel had dark and light gray phases. It is considered that the dark gray phase with higher Cr enrichment content acts as corrosion protective film mainly. CO2 corrosion resistance of 3%Cr martensitic steel was not affected by C content and tempering temperature because Cr enrichment content in the dark gray phase was high enough (more than 10 times of Cr content in mother metal).
The passivation behavior of SM400B carbon steel was investigated in 0.1 mol dm−3 carbonate solutions. The existence of carbonate in the solution reduced the critical current density for passivation, icrit, by virtually an order of magnitude in the pH range of 7.5 to 10.0 at 298 K. The critical potentials for passivation at the reduced icrit were within the potential-pH range where FeCO3 is thermodynamically stable. These results showed that carbonate accelerated the passivation tendency. Depassivation pH in the carbonate solution was determined to be 7.5 at 298 K by comparison between icrit and the diffusion-limiting current density for dissolved oxygen of 8.14 ppm. The depassivation pH is considerably lower than that of 9.3 in a solution that does not contain carbonate. The passivation tendency was enhanced with increasing temperature from 298 K to 363 K. The free corrosion potential, Ecorr, of polished specimens in the aerated carbonate solution at 298 K stayed in an active dissolution potential range in the early stages after immersion. They were, however, suddenly ennobled to the passive region after a long incubation time at pH≥8.0. The time dependency of Ecorr could be described from the viewpoint of electrochemical kinetics.