On the Cavitation Erosion Resistance of Coatings

Abstract

The propellers of ships have often been observed as damaged as a result of cavitation erosion. Although several investigations have been made on the problem of cavitation erosion of coatings by way of prevention against damage of propellers, the cavitation tests have been conducted under different test conditions with different test methods. This is the report of test conducted of 6 coatings (neoprene, polyurethane, electro nickel plating, electrochromium plating, flame sprayed colmonoy (fused) and welded high Al-bronze) with a view to determining their comparative efficacy for cavitation erosion resistance. A magnetostrictive cavitation test apparatus, a rotating-blade cavitation test apparatus and a water-tunnel cavitation test apparatus were used for the purpose. These coatings were applied to base Al-bronze. The results obtained are summarized as follows:
(1) In the magnetostrictive cavitation test, the electrochromium plating shows superior cavitation erosion resistance, but the flame sprayed colmonoy (fused) shows cavitation erosion 3 times as large as that in the electrochromium plating.
(2) In the rotating-blade cavitation test, the electrochromium plating shows superior cavitation erosion resistance, but the welded high Al-bronze shows cavitation erosion 10 times as large as that in the electrochromium plating.
(3) The ranking of cavitation erosion resistance of coatings in the water-tunnel cavitation test is the same as in the magnetostrictive cavitation test.