抄録
Amorphous Co-Ti alloys have been produced by both DC and pulse current plating from an acid sulfate bath, and their electrochemical properties in a sulfuric acid solution have been studied by means of electrochemical polarization measurements. X-ray intensities diffracted from the deposits were progressively lowered with increasing concentration of titanyl ion and faded away for DC-plated deposits containing 17.8mol% Ti. The pulse-plated Co-Ti alloys exhibited an amorphous phase with a high degree of homogeneity as well as high titanium content compared with DC-plated alloys. It is probable that the induced codeposition of amorphous Co-Ti alloys proceeds via the formation of a complex hydroxide, such as [Co⋅Tin(OH)2n+1]ad, as an adsorbed intermediate. The exchange current for catholic hydrogen evolution on the amorphous alloys was two orders of magnitude larger than that on pure cobalt deposits, whereas there were no differences in their corrosion resistance. This high activity for hydrogen evolution is ascribed to an increase in surface roughness caused by a selective dissolution of titanium from the amorphous alloy electrodes.
