GB1508852A - Sacrificial anode for cathodic protection of pipelines - Google Patents

Abstract

1508852 Cathodic protection of large-diameter pipes FEDERATED METALS CORP 26 June 1975 27156/75 Heading C7E A sacrificial anode 15 for protecting a pipe-line 16 comprises an even-numbered plurality of 4 to 8 arcuate anode segments 18 of sacrificial material, e.g. Al, Zn, Mg, each comprising at least one metal core 20 cathodic to the anode metal embedded therein except for at its ends, the anode segments 18 being adapted to be connected together in pipe embracing relationship (e.g. by welded joints 44), each anode segment having a maximum arc length equal to the circumference of the pipe divided by the number of anodes minus two and in the range 14 to 27 inches, there being around a pipe 4 segments for a pipe of diameter 20"-30", 4 or 6 for diameter 30"-36", 6 for diameter 36"-40", 6 or 8 for diameter 40"-54" and 8 for diameter 54"-72". The anode segments are made by casting around an elongate core; one or more core rods may be used, and one or more anode segments may be cast on the core rod(s); the requisite number are then fitted around the pipe and the core rods connected by welding. The pipe may have an insulating coating 17 of coal-tar enamel or coal-tar epoxy, and for sub-aqueous use may have an anti-buoyancy coating of concrete 57. Wires 58, 59 connect electrically the pipe and anode. The ratio anode thickness:pipe diameter may be 1:5-1:15 for pipe diameters 20-36" and 1:10-1:20 for diameter 37-72"; the ratio anode width:(total) anode core width may be 2:1-5:1 when at least 50% of the length of the core has width # 1" and thickness # 3/16", e.g. up to 7/16".