Abstract
Effect of the organic addition agent to acid stannous sulfate bath was studied by Hull cell test and cathode polarisation measurement. Crystal structure of the deposit from the bath was analysed by X-ray diffraction method.
Addition of organic compounds, such as wood tar, styrenated phenol, product of amin and aldehyde, that of amin and ketones, etc., to the acid stannous sulfate bath with surface activating agent (sodium n-octyl sulfate) made the polarisation potentials of tin, higher up to 130-400mV at 1.5A/dm2.
Brighting agents, lyophobic and weakbasic materials, gave good results in Hull cell test, and showed anionic action in diluted sulfuric acid solution.
These addition agents seem to form stable micelles as activating agent and complexes with tin ions in the solution.
Acting as carriers micelles and complexes would advantageously convey the brighting agent to the cathode.
In the solution over cathode surface of higher pH, micelles would probably lose their balance, and free lyophobic brightner adheres to the growing deposit.
Bright tin deposit has fine crystals, however, the brightness is mostly due to the orientation of crystals.
As to the full bright deposit, only one face (112, 330) was observed by X-ray diffraction.
