A process for protecting a metal structure in contact with a stream of sea water

摘要

823,531. Treating sea water by electrolysis. SOC. DE CONDENSATION ET D'APPLICATIONS MECANIQUES. Sept. 28, 1955 [Oct. 5, 1954; Feb. 11, 1955], No. 27639/55. Class 41. [Also in Group XVIII] A process for protecting a metal structure, e.g. a tubular condenser 1, in contact with sea water from scaling or from the formation of deposits of inert substances or living organisms, in which the water flows along a duct 2 towards the condenser, comprises providing in the duct 2 at least one electrolytic cell upstream of and insulated from the condenser 1, the condenser being reached by one at least of the products of anodic or cathodic reaction whereby the pH of the liquid in contact with the condenser is modified to cause inert substances in the sea water to remain or to become insoluble, the current density of at least one electrode of the cell being of the order of a few amperes per square metre. In one embodiment, Fig. 2, the anode 16, which is in the liquid supply conduit 2, is separated by a porous membrane 19 from the cathode 17 which is in a receptacle 21 leading to a drain duct 18. The positions of the anode and cathode may be reversed. In another embodiment, an aluminium or iron anode and cathode are disposed in the conduit 2 and depolarising alternating current is supplied to the electrodes, in addition to the electrolysis current supplied via rectifiers 12. The cathodes 25, 26, Fig. 4, may be of mesh form and enclose rod anodes 31, e.g. of iron or steel, connected in parallel, the cathodes thus acting as filters. A pump 27 delivers the treated sea water to the condenser 28 which is being protected, and cathodic lattices are arranged in the pump chamber 21 against the base and side walls thereof, the chamber 21 containing additional iron or steel anodes 311. Preferably, the cathodes comprise meshes 51 ... 54, Fig. 6, of the shape shown, and are supplied with current at a number of spaced, peripheral points 55 ... 58, the anodes 31 being U-shaped or channelsectioned members as shown. Additional electrode materials mentioned for all embodiments are lead, tin and chromium, and zinc is mentioned as an anode material. The cations derived from the anode (e.g. Fe, Al, Zn) form chlorides which by hydrolysis produce HCL which prevents precipitation of CaCO 3 . Specification 757,952 is referred to.