Anti-Fouling Metallic Materials for Underwater Ship Hulls (1st Report)

Abstract

10 kinds of metallic materials including newly developed copper alloys were investigated at first by the immersion test in natural sea water. After that, 4 kinds of anti-fouling metallic materials were investigated by the actual ship test conducted in the underwater ship hull of a car bulk carrier running in the Pacific Ocean for 16 months in order to make clear the corrosion resistance, anti-fouling properties and surface roughness of the materials.
The following results were mainly obtained by these tests. (1) The general corrosion was found on the almost all specimens attached to the underwater ship hull of car bulk carrier. There was no erosion found on any specimen of tested materials, though the speed of the carrier (7.8 m/sec.) exceeded the critical flow velocities (1-3 m/sec.) for copper and copper alloys in the case of heat exchangers using sea water.
(2) The anti-fouling properties of copper and copper alloys were able to be maintained with the dissolution of copper, that is the corrosion of copper and copper alloys.
(3) There was the slime attached to only a specimen of 90/10 Cu-Ni alloy mounted on the underwater ship hull. It is considered in the case of 90/10 Cu-Ni alloy that there was a possibility that the necessary antifouling properties were not obtained for the underwater ship hull.
(4) The surface roughness of all specimens attached to the underwater ship hull was in the range from 40μm to 70μm, which was smaller than that of ordinary anti-fouling paints.