The diffusivity and solubility of fluorine in solid nickel from electrochemical measurements
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he d i s s o l u t i o n of a t o m i c f l u o r i n e in solid n i c k e l obeys S i e v e r t s ' law; however, the s o l u b i l i t y r e s u l t s showed c o n s i d e r a b l e s c a t t e r 9 In the t e m p e r a t u r e r a n g e 1073 to 1223 K, the m e a n s o l u b i l i t y of f l u o r i n e i n solid nickel, c o r r e s p o n d i n g to the e q u i l i b r i u m Ni + NiF2, follows the r e l a t i o n s h i p : N ~ ( a t . pet) = 59
• 10 -3 exp((10,850 J/mol)/RT)
AT elevated t e m p e r a t u r e s ,
halogens, and halogen compounds a r e c o r r o s i v e to m e t a l s . The data a v a i l a b l e in the l i t e r a t u r e c o n s i s t s m a i n l y of the k i n e t i c s of m e t a l - h a l o g e n r e a c t i o n s and the morphology of p r o duct s c a l e s . The t h e r m o d y n a m i c s of f o r m a t i o n of m e t a l halides and t h e i r v a p o r p r e s s u r e s a r e a l s o a v a i l a b l e in the l i t e r a t u r e . D a n i e l and Rapp 1 have r e c e n t l y r e viewed the l i t e r a t u r e on the halogen c o r r o s i o n of metals. In o r d e r to u n d e r s t a n d the k i n e t i c s of m e t a l - h a l o g e n r e a c t i o n s , a detailed knowledge of the defect s t r u c t u r e and t r a n s p o r t p r o p e r t i e s in halides is n e c e s s a r y 9 Such i n f o r m a t i o n is a v a i l a b l e only for a l k a l i h a l i d e s and other compounds which a r e good solid e l e c t r o l y t e s (e.g., CaF2, BaF2, SrF2, MgF2, MnF2, PbF2, PbI2, PbBr2, and so forth). The k i n e t i c s of s e l e c t i v e i n t e r n a l h a l o g e n a t i o n of dilute alloys containing a more noble s o l v e n t and a m o r e r e a c t i v e solute is d e t e r m i n e d by the d i s s o l u t i o n and diffusion of halogen a t o m s into the alloy m a t r i x . The a u t h o r s 2 have r e c e n t l y p u b l i s h e d the r e s u l t s for f l u o r i n e diffusivity and s o l u b i l i t y in solid c o p p e r . T h e s e v a l u e s for f l u o r i n e in solid copper do not differ s i g n i f i c a n t l y f r o m the c o r r e s p o n d i n g v a l u e s for oxygen diffusivity and s o l u b i l i t y in solid copper 9 No other data a r e a v a i l a b l e in the l i t e r a t u r e c o n c e r n i n g the s o l u b i l i t y and diffusivity of halogens in m e t a l s 9 Nickel is the m e t a l m o s t r e s i s t a n t to attack by dry g a s e o u s f l u o r i n e due to the f o r m a t i o n of a compact NiF2 scale of low v o l a t i l i t y which p r o t e c t s the m e t a l s u b s t r a t e . The k i n e t i c s of the n i c k e l f l u o r i n a t i o n r e action have b e e n studied e x t e n s i v e l y as a function of S. N. S. REDDY, formerly with The Ohio State University, is now Research Engineer, Amoco Research Center, Naperville,IL 60540. ROBERT A. RAPP is Professor, Department of Metallurgical Engineering,The Ohio State University, Columbus, OH 43210. Manuscript submitted February 28, 1979. METALLURGICAL TRANSACTIONS B
t e m p e r a t u r e , f l u o
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