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a l l o y c a s t i n g s exhibit good s t r e n g t h vs weight p r o p e r t i e s c o m b i n e d with f a v o r a b l e c o r r o s i o n r e s i s t a n c e to m a r i n e e n v i r o n m e n t s . However, such c a s t i n g s a r e u s e d in v a r i o u s h e a t - t r e a t e d conditions and the a t t e n d a n t m o d i f i c a t i o n s in m i c r o s t r u c t u r e p l a y a s i g n i f i c a n t r o l e in e s t a b l i s h i n g c o r r o s i o n b e h a v i o r . P r e v i o u s w o r k on the c o r r o s i o n of a l u m i n u m a l l o y s h a s f o c u s s e d on the p i t t i n g b e h a v i o r of wrought m a t e r i a l s l-a and the effect of c o p p e r t h e r e o n . C o p p e r in a m o u n t s up to 0.15 wt p c t h a s b e e n found to r e d u c e s u s c e p t i b i l i t y to t n t e r g r a n u l a r c o r r o s i o n and p i t t i n g due to an i n c r e a s e in the n u m b e r of a c t i v e c o r r o s i o n s i t e s , l e a d i n g to 'enh a n c e d g e n e r a l c o r r o s i o n , s P a g a n e l l i concluded that the c o r r o s i o n r e s i s t a n c e of s e m i w r o u g h t a l u m i n u m - 5 wt p c t c o p p e r a l l o y can be i m p r o v e d b y e x t e n d i n g the d u r a t i o n of a r t i f i c i a l aging b e y o n d that r e q u i r e d for o p t i m u m m e c h a n i c a l p r o p e r t i e s . 6 G a l v e l e , et al., c o n ducted a d e t a i l e d s t u d y of i n t e r g r a n u l a r c o r r o s i o n in aged, wrought a l u m i n u m - 4 wt p c t c o p p e r a l l o y . 7 They e s s e n t i a l l y r e g a r d e d the a l l o y a s b e i n g c o m p r i s e d of t h r e e " p h a s e s " : a l u m i n u m - 4 wt p c t c o p p e r g r a i n body, A12Cu p r e c i p i t a t e , and a l u m i n u m - 0 . 2 wt p c t c o p p e r d e nuded g r a i n b o u n d a r y ; i n t e r g r a n u l a r c o r r o s i o n o c c u r r e d under t h o s e conditions of e n v i r o n m e n t and p o l a r i z a t i o n l e a d i n g to p i t t i n g of the a l u m i n u m - 0 . 2 wt p c t c o p p e r " p h a s e . " While none of t h e s e a u t h o r s have i n v e s t i g a t e d the c o r r o s i o n b e h a v i o r of c a s t - a l u m i n u m - c o p p e r a l l o y s . Bond, et al., 8 found that m i c r o s e g r e g a t i o n of r e s i d u a l i m p u r i t i e s (iron, c o p p e r , s i l i c o n ) in high p u r i t y a l u m i n u m l e d to f i n e - s c a l e p i t t i n g in an o x i d i z i n g c h l o r i d e e n v i r o n m e n t , while h o m o g e n e o u s s p e c i m e n s r e m a i n e d f r e e of p i t s . Due to the g r e a t e r m i c r o s t r u c t u r a l c o m p l e x i t y of c a s t a l l o y s in c o m p a r i s o n to wrought m a t e r i a l s the p r e s e n t i n v e s t i g a t i o n was u n d e r t a k e n to e s t a b l i s h in a s y s t e m a t i c m a n n e r the effect of c o p p e r d i s t r i b u t i o n on the c o r r o s i o n b e h a v i o r of an a l u m i n u m - 4 . 5 wt p c t Y. V. V. R. S. MURTY is Graduate Ass