The effects of bath composition, current density and temperature on cathodic polarization, cathodic current ef®ciency of codeposition, composition and structure of Co±Cu alloys electroplated on a steel substrate from citrate baths have been studied. Addition of boric acid to citrate electrolyte increases the percentage of Co in the deposits and improves the quality of these deposits. The cathodic current ef®ciency of the baths is relatively high and increases with increases in the metal content in the bath and the current density but decreases with temperature. The composition of the deposit is controlled by the applied current density. At low current densities, Cu-rich alloys were obtained. At higher current densities, the composition of the alloys was controlled by the limiting current density of Cu codeposition. The Co content of the deposits increases with increases in the metal content in the bath and the temperature. The structure of the deposited alloys was characterized by anodic stripping and X-ray diffraction techniques. The deposited alloys consisted of a single solid solution phase with a face-centred cubic structure.

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The influence of HAF carbon black and BaTiO 3 ceramic powder contents in SBR vulcanizates on the dielectric constant (e 0 ) at different frequencies and at fixed temperature of 303 K is studied well in this article. The temperature dependence of the ac conductivity (s ac ) was also studied. e 0 appreciably decreases as frequency increased for both filled and unfilled SBR vulcanizates. At each frequency, e 0 gradually decreased with BaTiO 3 loading, but its change at any fixed frequency with BaTiO 3 filler loading is not uniform. For HAF group e 0 (at loading 40 phr), drops rapidly with frequency. Meanwhile, it increased appreciably beyond a certain HAF filler loading (% 20 phr). Experimental values of the dielectric constant of both BaTiO 3 and HAF contents were compared with those calculated by using Tsangaris, Clausius and Bruggman models. Tsangaris model with simple modifications was applied and a fairly good agreement was obtained. The HAF particles or aggregates was found to take the shape of oblate ellipsoids with the minor axes parallel to the applied frequency as detected from the decreasing behavior of the depolarizing factor (Y) with HAF contents.

Thc clectrocheniical behavinur of a Cd anode was inves(igated in 0.05-2 M NaOH solutions by the potenliodynamic technique.The polarization curves exhibit active to passive transition prior to oxygen evolution. The threshold potential of the active dissolution is very close to the reversible potential o r the system Cd/Cd(OH)2. X-Ray diffraction and XPS measurements rcveal that thc passive layer is composed of both Cd(OH)z and CdO. The influence of increasing amounts of CI-, Br-or 1 ions on the anodic lxhaviour of Cd i n NaOH solution has been investigatcd. The halides stimulate the anodic dissolution in the active region and tend to break-down the passive layer in the passive region. leading to pitting attack. The pitting potential shifts to more negative values with increasing halide ion concentration but to thc reverse direction with increasing alkali concentration.Das clektrochemische verhalten einer Cd-Anode wurde in 0.05 bis 2 hl NaOH potentiodyriamisch untersucht. Dic Polarisationskurven Leigen vor der Saucrstoffcntwicklung Aktiv-I'assiv-Ubergang. Das Sch\~~clleiipotcntiaI der aktiven Aufliisung liegt aehr nahc am revcrsiblen Potential des Systems Cd/Cd(OH)2. Riintgenbcugung und XPS-Analyse zeigen, dal3 die Passivschicht aus sowohl CdO als auch CLI(O€T)~ besteht. Der EinfluR steigcnder Mengen von Chlor-, Erom-und Jodionen auf das anodische Vcrhalten von Cd in NaOH wurde untersucht. Die Halidionen stimulieren danach die anodische Auniisung im aktiven Bereich uncl durchbrcchen die Passivschicht im passivcn Rercich. so daB Lochkorrosion auftritt. Das Lochkorrosionspotential verschiebt sich mit zunehmendcr Halidionenkonzentratiori nach negativeren. init zunehmender Alkalikonzentration jcdoch nach posiliveren Werten.

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