GB902667A - Anode for cathodic protection of ships - Google Patents

Abstract

902,667. Preventing corrosion. PREISER, H. S. Dec. 5, 1958, No. 39271/58. Class 123 (1). An impressed current D.C. energized anode system for protecting a ship's steel hull from corrosion comprises a D.C. generator 6 having its negative terminal 8 grounded through a three-way switch 14 and its positive terminal 10 connected by a flexible waterproof cable 12, e.g. 200 feet long, to an electrochemically insoluble anode 11 which has a weight per foot corresponding to that of the cable 12 for trailing at least 500 anode diameters away from the ship. The switch 14 can be operated to connect the hull 5 through terminals 15, 16 to forward and stern electrodes 17 and 18 of a reference voltameter to measure the oxidation reduction potential, and thus the corrosion resistance, of the hull 5. Polarization occurs accompanied by the formation of a protective coating of calcium carbonate precipitation on the hull 5. An anode, Fig. 3, comprises a silver rod 11 which is clad with a 0.005 inch thick layer of pore-free platinum and is soldered at 25 to a conductor 24 of the cable 12. The joint is sealed by a rubber sheath 27 and a thermoplastic covering 28. Vanes and stabilizers may be fitted to an anode. As shown in Fig. 4, a cable 46 wound on a reel 44 mounted on the deck 40 of a ship 30 and passing through a rubber or plastic lined pipe 38, having gate valves 50, into the sea, carries a trailing anode rod 48. An anode rod, Fig. 5, not shown, comprises a silver or copper rod which is threaded at one end for attachment to a cable and has a non-porous coating of tantalum or titanium of about 0.010 inch thick and a very thin layer of platinum or palladium of about 0.00025 inch applied as a cladding or plating. A variable weight hollow rod is described which is closable by end plugs and can be filled with the desired amount of ballast such as plastics and sand. In a further modification, Fig. 7, a conductor of the cable 74 is soldered to a cylindrical tantalum connector so that the other end of which has a threaded recess for attachment to a trailing anode 76. The joint is covered by a tapered rubber sleeve and a twopart screw-engageable collar 84, 90. An arrangement, generally similar to that shown in Fig. 7, may be adapted for a cable having a central steel core.