Corrosive Wear of Bronze Propeller Shaft Sleeve (Part 2; Wear Control by Cathodic Protection and Application to an Actual Ferry)

Abstract

The previous report described corrosive wear of propeller shaft sleeves made of bronze in seawater-lubricated stern tube bearings, as well as the occurrence of craters on the sleeve surface due to the action of erosion corrosion. Based on the mechanism, this second report provides the development of an impressed current cathodic protection method that prevents the corrosion of the sleeve surface and reduces wear. Using Pt/Ti anodes installed in some of the water channel grooves for the rubber bearings, this method is characterized by intermittent protection, and protection conditions were investigated by means of fundamental tests using bearings 140 mm in diameter. As a result, a current density of 8 A/m 2 was found to protect the sleeve from corrosion, and it was confirmed that the sleeve wear was reduced. Cathodically protected bearings were applied to bearings 500 mm in diameter equipped for an actual ferry vessel, and the results are presented here in terms of bearing design, trial running, and in-service progress. Presented at the STLE Annual Meeting, in Toronto, Ontario, Canada, May 17-20, 2004, Review led by Jim Netzel