No abstract

The present investigation deals with the electrodeposition of tin from chloride electrolytes. Gelatin, b-naphthol, polyethylene glycol, peptone and histidine were used as additives in the plating bath to improve the surface morphology, grain size, smoothness and corrosion resistance of the tin deposits. XRD data obtained for electrodeposited tin show polycrystalline nature with single b-phase and tetragonal structure. A uniform and pore free surface was observed under SEM analysis. AFM results indicate the grain refining brought about by the additives. Corrosion rate measurements using the Tafel extrapolation method and electrochemical impedance spectroscopy reveal the increased corrosion resistance from baths containing additives.

This paper deals with zinc plating from an acetate electrolyte and the resultant deposit properties. The addition of thiamine hydrochloride and gelatin to the plating bath improves the corrosion resistance and surface morphology of the zinc deposits. The XRD pattern obtained for electrodeposited zinc show a polycrystalline nature with a hexagonal structure. A uniform and pore free surface was observed under SEM analysis.

Electrodeposition of copper was done with different molecular weight (MW) polyethylene glycol (PEG) as an additive in the plating bath. The adsorbed layer formed of PEG and chloride ion (Cl − ) in the presence of copper ions has a definite role in controlling the deposition mechanism and the coating characteristics. The adsorption behaviour and suppressor nature of PEG with different MW (200-20000) on the physicochemical and the surface morphological features of the copper deposit were characterized. The results reveal that depending on the adsorption capacity of the intermediate complex, the deposit properties show gradation. There is a range of morphology with particular grain structure for different MW PEG addition. Grain size and the roughness decreased with increase in PEG MW. The concentration of Cl − ion in the plating bath is also significant in determining the deposit mechanism of the bath as revealed from the shift in cathodic potential. The adsorbing power of the complex depends not only on PEG MW but also on Cl − ion concentration. XRD analysis of the copper deposit obtained with low MW PEG showed (220) as the major plane and with high MW PEG the prominent orientation was (111) and (200).

Sn-Ni alloy coatings on mild steel substrates produced by selective area deposition process with layer thickness of about 14 lm were investigated with regard to the structural and corrosion properties. X-ray diffraction analysis revealed that the selective area plated Sn-Ni alloy was heterogeneous and composed of NiSn, Ni 3 Sn 2 and Ni 3 Sn 4 phases. Uniform surface coverage of the substrate by granular morphology was observed from SEM and AFM. The alloy composition was determined by X-ray fluorescence (XRF). The corrosion protection performance of Sn-Ni alloy on mild steel was assessed using salt-water immersion and electrochemical corrosion tests. A sharp decrease in I corr and high charge transfer resistance indicated improved corrosion resistant behavior of the selective area deposited Sn-Ni alloy.