Broad and practical guidelines are necessary on how an LCM system for a port structure can be set up and run from the beginning until the system is phased out at the end of the service life of the structure. The owner particularly needs a comprehensive database recording the history of the establishment and life of the port structures up to the present date, as well as of the works and developments carried out over the years by the application of LCM. And where a large number of structures are included in the inspection program, application of the contemporary database computer software offers numerous advantages over traditional ways of collecting and storing inspection data. In accordance with the LCM report by WG31, the outline of the guidelines for the establishment and operation of the LCM system and an example of computerized database in Los Angels Port are presented.
The cathodic protection by impressed current system was applied to a coated steel channel, which had been used for 40 years and leads river water to its filtering plant. The flowing rate of water was 1.8m/s. The formation of electrocoating on the damaged and corroded area of coating was examined. At the same time, the effect of the formed electrocoating on potential distribution and polarization behavior were studied. Cathodic current density was maintained at 10mA/m2 for 143 days and at 25mA/m2 for the following 140 days. When the impressed current density was 10mA/m2, neither the potential nor its distribution was improved by time. Instead, at 25mA/m2, the potential was moved toward the negative and the potential distribution became uniform. After the test, it was observed that electrocoating was formed not only on the surface of tubercles but also in their rust layers. The formation of effective electrocoating and the uniform potential distribution made the application of cathodic protection very feasible to this coated steel channel.
The effect of iron sulfide on the cathodic reactions was studied in anaerobic conditions for the purpose of analyzing the corrosion mechanism in the seawater containing hydrogen sulfide. The iron sulfide was formed under both natural corrosion conditions and anodic polarizations. In the case of natural corrosion, the existence of iron sulfide film increased the cathodic current to a certain extent. The anodically formed iron sulfide enhanced the cathodic reaction considerably. Cathodic current at a constant potential was strongly dependent on anodic potential at which iron sulfide was formed. The open circuit corrosion potentials of steel covered with iron sulfide were also a function of anodic potential for iron sulfide formation.
This paper describes results of examinations to investigate the influence of tidal zone environment on cathodic current density for cathodically protected marine steel structure. Cathodic polarization at a fixed potential was conducted in the simulated tidal zone condition with the alternate exposure to air and 3%NaCl solution in which concentration of dissolved oxygen changed periodically. Consequently, the following results were obtained. Cathodic current density was maximum, immediately after rusted carbon steel was immersed in the solution. The maximum cathodic current density of rusted carbon steel was 1.00A/m2 or more, which was about 6 times more than that of bare carbon steel, and about 60 times more than that of carbon steel covered with calcareous deposits.