The system described in the paper is an extension of the cathodic protection that is available from sacrificial anodes of zinc or aluminum. Sacrificial anodes in general terms will give out about 1 amp of current per one foot length. The stern of a small ship might receive between 10 and 15 amps of cathodic protection. The impressed current system operates at 2 to 3 times this current. An ocean going tug might consume a maximum of 60 amps; of this between 10 and 15 amps will be consumed by the propeller and the nozzle combination. This is probably twice the current that would be available using a simple brush mechanism and sacrificial anodes. The level of protection at the stern in the area of the propeller is about 150 mV more protected than the accepted potential criterion and when the propeller is in a nozzle then the potential at the aperture of the nozzle would be about 250 mV overprotection. This overprotection can best be achieved using anodes of low current output per unit length, sited close to the propeller. These will give overprotection without putting a high potential stress across the paint system and the possibility of failure of the protection if the paint is damaged.

Media Info

  • Features: References;
  • Pagination: p. 1007-14

Subject/Index Terms

Filing Info

  • Accession Number: 00138278
  • Record Type: Publication
  • Source Agency: Offshore Technology Conference
  • Report/Paper Numbers: V3, OTC 2704 Proceeding
  • Files: TRIS
  • Created Date: Sep 4 1976 12:00AM