The electrodeposition of Tin/Zinc, Tin/Chromium and Tin/Zinc/Chromium alloys

• Main Author: Brooke, Ian William
• Published: Glasgow Caledonian University 2005
• Subjects: 671.732
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426444

The electrodeposition of tin/chromium and tin/zinc/chromium is a new field of research. This field was investigated because it may be of commercial, as well as scientific, interest if a range of alloy compositions could be sustainably deposited from environmentally acceptable electrolytes. With no published work to guide this research difficulties were encountered in producing sustainable deposition procedures. A novel electrolyte that deposited tin/chromium alloys in a range of compositions was produced. This electrolyte was adjusted to produce novel tin/zinc/chromium deposits in a range of compositions. However the thickness of deposited tin/zinc/chromium was limited to 300nm. It was hypothesised that polymerised chromium glycine could be used as a weak brightener to increase deposit thickness. This produced another novel electrolyte and it was confirmed that chromium could be codeposited from polymerised chromium glycine with tin and zinc. This electrolyte produced deposits in a range of compositions and produced tin/zinc/chromium deposits up to 3Jlm thick. The ability to deposit chromium from the polymerised electrolyte was enhanced by the codeposition oftin. This induced codeposition of chromium with tin had not previously been reported. It was observed that tin metal was dissolved by the chromium glycine electrolyte and that this dissolved tin was not precipitated out. It was suggested that the dissolved tin could be electrodeposited with chromium. Experimentation confirmed this hypothesis. The alloy produced was rich in chromium, 6Jlm thick and of a bright appearance. Tin/chromium and tin/zinc/chromium deposits were analysed by Mossbauer and X-ray Diffractometry and p-tin identified in all samples examined. Significantly tin only phases could not explain the Mossbauer and X-ray diffraction results, the presence of other tin microenvironments are required. However the lack of standards for comparison made identification of such microenvironments difficult.