Inhibiting Mossy Zinc Electrodeposits from Ammoniacal Media with Hydrophobic Tetraalkyammonium Salts

Abstract

The effect of tetraalkyammonium chlorides (TAACs) with different numbers of long alkyl chain (-C H ) on zinc electrodeposits in the ammoniacal media was systematically investigated by voltammetric measurements, scanning electron microscopy and X-ray diffraction. It was found that the inhibition effect of TAACs on mossy zinc deposits increases with increasing their hydrophobicity. The hydrophobic TAACs can improve the smoothness and crystallinity of zinc deposits and change the most preferred orientation. Meanwhile, the inhibition effect of hydrophilic octyltrimethylammonium chloride (OTAC) on mossy zinc deposits can be enhanced with increase of OTAC concentration. The improvement on the smoothness of zinc deposits with hydrophobic methyltrioctylammonium chloride (TOAC) is dependent on the pH of electrolyte. The presence of saturated TOAC at pH 7.5 can produce better zinc deposits with higher smoothness. The inhibition mechanism of both hydrophilic and hydrophobic TAACs on mossy zinc deposits has been elucidated. These results will allow the morphology of metal deposits to be better controlled by the specific organic additives. 8 17