Effect of Electric Resistance of Racking Devices on Current Distribution in Chromium Plating of Piston Rings
Metal distribution on a set of piston rings assembled on a racking device as a cylinder (Fig.l) was studied. Chromium plating solution used contained (g/1): Cr03 240-260; H2S04 0,8-1,2; NaSiF6 3,6-4,0; Cr 3+ 2,0-4,0; Fe3+ <11. Operating conditions are given in Table 1 (t 55°C). Experimental data (Fig.2-5) reveals two areas of diminished thickness on rings located at relatively larger distances from the points of electric contacts, thus indicating on the possible contribution of insufficient conductivity of metal part of the whole electric circuit. Calculations (Fig.7) made by the authors (table 2) on the basis of an equivalent circuit (Fig.6) have proved an appreciable contribution of metal conductance to the current distribution.