Effect of various additives on morphological and structural characteristics of pulse electrodeposited tin coatings from stannous sulfate electrolyte

摘要

The pulse electrodeposited tin coatings are synthesized from an acidic electrolyte (stannous sulfate, SnSO_430 g/L and sulfuric acid, H_2SO_4-200 g/L) containing various additives (polyethylene glycol (PEG), thiourea and Triton X-100). The effect of the additives on surface morphology, preferred orientation of grains, grain size, and surface roughness has been studied. The final coatings are characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and surface profilometry. In the absence of additives, tin deposition is associated with prominent hydrogen evolution reaction giving rise to rough deposits. Both PEG and thiourea act as grain refiner while Triton X-100 acts as a brightener in the electrolyte. The cathodic polarization on the reduction of the tin (Ⅱ) ions is more pronounced when a combination of additives is used and further, fine-grained, smooth and shiny electrodeposits of tin are obtained due to a synergistic effect of the adsorbed species.