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s t u d i e s on the i n t e r n a l oxidation of dilute C u - T i a l l o y s have i n d i c a t e d the p r e s e n c e of s e v e r a l Ti o x i d e s in the p r e c i p i t a t e s f o r m e d in the Cum a t r i x . 1'2 While this is not s u r p r i s i n g on t h e r m o d y n a m i c grounds, the s t r u c t u r e of the oxides f o r m e d at v a r i o u s d i s t a n c e s b e l o w the s p e c i m e n s u r f a c e as the i n t e r n a l oxidation f r o n t a d v a n c e s is i m p o r t a n t f o r u n d e r s t a n d i n g the d e t a i l s of the i n t e r n a l o x i d a t i o n p r o c e s s . U n f o r t u n a t e l y , f r o m t h i s standpoint, the T i oxide p a r t i c l e s f o r m e d in Cu a r e e x t r e m e l y s m a l l 1 and m a k e a d e t a i l e d s t r u c t u r a l a n a l y s i s difficult. T h e r e f o r e , a study of i n t e r n a l o x i d a ti o n in the C o - T i s y s t e m w as u n d e r t a k e n s i n c e one would e x p e c t l a r g e r oxide p a r t i c l e s to f o r m in a Co r a t h e r than Cu m a t r i x . F u r t h e r m o r e , s i n c e no d e t a i l e d s t u d i e s of i n t e r n a l o x i d a t i o n in C o - b a s e alloys have b e e n r e p o r t e d , a study of the k i n e t i c s of i n t e r n a l o x i d a t i o n of C o - T i a l l o y s o f f e r e d the opportunity to d e t e r m i n e the p e r m e a b i l i t y of o x y gen in Co. T h e f o r m a t i o n of two o r m o r e o x i d e s by i n t e r n a l ox i d at i o n has been o b s e r v e d in s e v e r a l s y s t e m s but the p h e n o m e n o n has not b e e n a n a l y z e d in m o s t c a s e s . T h e w o r k of L e v y and N i e s s e n 3 on the i n t e r n a l o x i d a t i o n of A g - M n a l l o y s i n d i c a t e s the f o r m a t i o n of MnO at 750~ but s u g g e s t s the f o r m a t i o n of m o r e than one oxide at 910~ The f o r m a t i o n of Mn2Os and MnsO4, as w e l l as MnO, was r e p o r t e d f o r i n t e r n a l l y o x i d i z e d C u - M n alloys.4 Both SnO and SnO2 a r e f o r m e d in A g Sn a l l o y s , s and both Fe304 and CuFeO2 a r e f o r m e d in C u - F e a l l o y s o x i d i z e d at high oxygen p r e s s u r e s . 6 . T h e m o s t d e t a i l e d study of the f o r m a t i o n of m u l t i p l e o x i d e s by i n t e r n a l o x i d a t i o n i s the w o r k of K a p t e i j n 7 on the i n t e r n a l ox i d a ti o n of A g - C u a l l o y s . In t h i s s y s t e m , the oxide p a r t i c l e s n e a r the i n t e r n a l o x i d a t i o n f r o n t w e r e Cu20 which was f u r t h e r o x i d i z e d to CuO as the l o c a l oxygen a c t i v i t y w a s i n c r e a s e d by the i n w a r d d i f f u s i o n of oxygen f r o m the s p e c i m e n s u r f a c e . An i n t e r m e d i a t e zone containing both CuzO and CuO w as o b s e r v e d b e t w e e n the Cu20 and CuO r e g i o n s . T h e o x i dation k i n e t i c s w e r e a n a l y z e d u s in g a m o d e l due to M e i j e r i n g 8 which is r e v i e w e d in Appendix A. In s h