with temperature as well as current density this kind of nodular deposit is believed to be a consequence of concentration polarization due to the high average current density used cracks in the deposits are believed to be formed by the decomposition of chromium hydride this decomposition results in a volume change thereby restraining the deposits in the plane of the base metal and creating surface cracks during the reaction chromium hydride decomposes to chromium and hydrogen gas this process seems to have created the cracks and holes shown in fig3 and fig4 although all deposits show a nodular surface the cross sectional view reveals the two dimensional laminar structure as shown in fig4 the distance between laminae increases with increasing temperature and with decreasing current density it is possible that a viscous cathode film forms and then is broken down in a periodic way as shown in fig5 these phenomena take place more frequently at lower temperatures and higher current densities x ray diffraction patterns of bulk chromium and as deposited trivalent chromium are shown in fig6 electroplated hexavalent chromium has a 111 preferred orientation and bcc structure while trivalent chromium reveals only the 110 peak and not at the same position as aged bulk chromium as shown in fig6 b trivalent chromium was believed to have a simple cubic structure with 210 preferred orientation but results in this work reveal the bcc structure with 110 preferred orientation the grain size of as deposited chromium is about 30 35 u00e5 these extremely fine grains in chromium deposits have been explained as resulting from hydride decomposition the variation of microhardness with electrolyte temperature and the variation with current density of both trivalent and hexavalent chromium deposited at 55 u00b0 c 40 a dm 2 are shown in.