| 摘要 |
803,864. Preventing corrosion. DOW CHEMICAL CO. Jan. 13, 1956 [Feb. 1, 1955], No. 1295/56. Class 123(1) Sacrificial anodes for the cathodic protection of metallic structures are provided with closely-fitting electrically-insulating, liquid impervious coatings provided with perforations of such size, number and distribution that the total current flow to the cathodic structure and especially the flow to the parts thereof adjacent the anode are limited, whereby the anode life is extended and the area protected is increased. In one form, Figs. 1 and 4, the anode assembly 20 consists of a magnesium block 22 having two metal core straps 24 extending therefrom as mounting lugs 24a. The anode is encased in a closely-fitting cover 26, for example, of neoprene or polyvinyl chloride resin which also extends along part of the length of the lugs 24a, the cover being applied by dipping, spraying and painting. The top of the cover has holes 28 therethrough of a number and size to give the required current output from the anode. When the anode is to be used in sea water it may be provided with an anti-fouling coating, e.g. a copper salt of polyacrylic acid. Slowly soluble coatings such as polyacrylic acid or polyvinyl alcohol may also be used to provide a delayed action anode which will come into operation when an immediately operative anode has been consumed. In another form, Fig. 7, the anode assembly consists of an anode 42 in which is embedded the end of a cable 44, the anode having a plastic covering 46 provided with perforations 48. As shown in Fig. 8, the cable 64 extends right through the anode body 66, the perforated plastic covering 62 being extended along the cable to prevent strong local current flow. Specification 803,863 is referred to. |
