| Abstract: | This paper describes an exploratory survey of alternatives to conventional electrically conducting welding primers, which suffer from the disadvantage that the very high proportion of conducting filler needed to give adequate conductivity for welding places severe limitations on the composition of the primer.It is shown that nickel powder is a very much more effective conducting filler than non-magnetic metal powders such as zinc. The nickel particles by virtue of their mutual magnetic attractions form chains of low electrical resistance, whereas for non-magnetic powders, the inter-particle attractions and the probability of inter-particle contacts are much less.It is possible to make coating compositions containing only moderate proportions of nickel powder which have adequate conductivity for welding. These compositions have been covered by patent.? The nickel powder does not appear to affect the protective qualities of the coating adversely. The main disadvantages in the use of nickel as a conducting filler are its high price and the tendency, in common with most other metallic fillers, for the rate of settlement to be high. |
