The present work was undertaken to find out the true bonding strength of copper plating on iron, using a strike solution and a plating solution. To obtain a thick plating of 1 mm thickness, a low current density of 0.7 A/dm
2 and a long plating time of 70∼80 hr were adopted. After the deposition of copper, we obtained a copper disc of 1 mm thickness with a stem of iron rod. The groin part was turned on a lathe to get a smooth joint. Then it was set into a special chuck and drawn for the tensile test.
The bonding strength of copper plating on iron rod varied naturally according to the surface finish of iron viz. 13.5 kg/mm
2 for 120 mesh emery paper finish, 19.0 kg/mm
2 for 280 mesh emery paper finish and 26 kg/mm
2 for buff finish. For the purpose of referrence the strength of commercial electrolytic copper having 11 mm thickness was measured in longitudinal, transverse and thickness directions. It is shown that the tensile strength is 25 kg/mm
2 irrespective of the applied directions.
This fact means that the bonding strength of copper plating on iron is nothing but the plated copper itself and the true bonding strength between copper and iron was inmeasurable in the present work.
The bonding strength of copper plating on ferritic ductile iron was also investigated. Six rods of 4 mm diameter of ductile iron were similarly plated with copper. The mean bonding strength was 23 kg/mm
2, and the fracture showed copper red on the ferritic groundmass and grey on the nodular graphite. Using the Halbert Counter, linear analyses were made on 10 segments of straight lines and the bonding strength was calculated to be 23 kg/mm
2, assuming the bonding strength of copper plating on ferrite to be 26 kg/mm
2 and that of graphite to be 2 kg/mm
2.
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