The propellers of identical trawlers were examined after they had been in service for periods of up to two years. The propellers had a diameter of approximately 3.3 m; their blades were made of Ni-Al bronze G-Cu Al9NiFeMn (Standard TGL 8110 (7.603), containing 7--11 percent Al, 2.5--6.5 percent Ni, 3--5 percent Fe, 1--3 percent Mn, and the remainder Cu) and their hubs of stainless steel GS-X8CrNi14.1 (14 percent Cr). The examination included metallographic testing of the surface and chemical analysis. A dense cathodic surface layer developed shortly after the propellers were placed in service. This layer affected adversely the passive layer of the metal surface, and the damage thus caused made the propeller prone to roughening by an erosion-corrosion process. Plastic coatings on the propeller surface may provide a remedy; also, on the basis of theoretical considerations, it is indicated that a high protective current (that would require the provision of cathodic protector with external current) may contribute to the development of a porous surface layer that would, in turn, counteract the erosion-corrosion process.

  • Authors:
    • Bohm, D
  • Publication Date: 1968

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Filing Info

  • Accession Number: 00014631
  • Record Type: Publication
  • Source Agency: Joint Publications Research Service
  • Report/Paper Numbers: German
  • Files: TRIS
  • Created Date: Aug 12 1971 12:00AM