Evaluation of zinc sulfate electrolytes by cyclic voltammetry and electron microscopy
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cathode d e p o s i t . If this is not p r o p e r l y m a i n t a i n e d and r o u g h o r i r r e g u l a r s u r f a c e s a r e obtained, then l o w e r e d c u r r e n t e f f i c i e n c i e s and d i f f i c u l t i e s with p h y s i cal h a n d l i n g c a n r e s u l t . T h i s p r o b l e m is not unique to z i n c winning, however, as s i m i l a r s i t u a t i o n s a r e e n c o u n t e r e d with m a n y o t h e r p l a t i n g p r o c e s s e s . One c o m m o n p r a c t i c e to a s s i s t in m i n i m i z i n g d e n d r i t e f o r m a t i o n i s to make a d d i t i o n s of about 10 to 40 p p m of o r ganic r e a g e n t s , s u c h as glue o r gum a r a b i c , to the electrolyte. However, at p r e s e n t , t h e r e a r e no s a t i s f a c t o r y m e thods for c h e c k i n g the c o n c e n t r a t i o n of the o r g a n i c r e a g e n t in the z i n c cell a c i d . Only the p h y s i c a l r a t e of addition o r weight of glue put into the c e l l is known. T h u s , d i r e c t o b s e r v a t i o n of cathode growth i s about the only a v a i l a b l e m e a n s of e v a l u a t i n g the c o n d i t i o n of the e l e c t r o l y t e . T h i s c a u s e s a c o n s i d e r able t i m e l a g b e f o r e c o r r e c t i v e a c t i o n can be t a k e n . It i s a l s o p o s s i b l e for r a t h e r e x t r e m e v a r i a t i o n s i n the e l e c t r o c h e m i c a l b e h a v i o r of the e l e c t r o l y t e to o c c u r i n a r e l a t i v e l y s h o r t t i m e , with few if any c l u e s a s to the c a u s e o r r e m e d y . A l s o , i n t e r a c t i o n s b e t w e e n the o r ganic and c e r t a i n o t h e r i n o r g a n i c s p e c i e s in s o l u t i o n c a n o c c u r , 6 adding s t i l l a n o t h e r d i m e n s i o n to the control problem. Some w o r k has b e e n p e r f o r m e d on the a n a l y t i c a l d e t e c t i o n of i m p u r i t i e s in z i n c e l e c t r o l y t e s v,8 u s i n g c u r r e n t - p o t e n t i a l r e l a t i o n s h i p s , but t h e s e have not gained wide a c c e p t a n c e . T h i s t e c h n i q u e was a l s o u s e d for a n a l y z i n g i m p u r i t y c o n c e n t r a t i o n s i n m a n g a n e s e s u l f a t e e l e c t r o l y t e s . 9 Although s u b s t a n t i a l r e s e a r c h has b e e n conducted on the p r o c e s s e s i n v o l v e d i n m e t a l d e p o s i t i o n in the p r e s e n c e of o r g a n i c c o l l o i d s and o t h e r c h e m i c a l r e a g e n t s , 1~ little p r a c t i c a l u s e s e e m s to have b e e n made of the r e s u l t s . T h e r e has a l s o b e e n c o n s i d e r a b l e r e s e a r c h on the m e c h a n i s m s of m e t a l d e p o s i t i o n at s o l i d e l e c t r o d e s u s i n g both s i n g l e and c y c l i c v o l t a m m e t r y techniques.12-~4 E v e n though s u c h s t u d i e s a p p e a r to be of p o t e n t i a l value, t h e r e have b e e n few e x a m p l e s w h e r e the data o r t e c h n i q u e s have b e e n a p p l i e d to t
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