Diffusion of hydrogen in iron
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A m a s s s p e c t r o m e t e r was used to study hydrogen diffusion and t r a p p i n g p h e n o m e n a in fullya n n e a l e d and slightly c o l d - w o r k e d pure i r o n s p e c i m e n s which were in contact with d i s t i l l e d water or dilute acidic Buffer s o l u t i o n s . In the case of f u l l y - a n n e a l e d i r o n and slightly coldworked i r o n , hydrogen can diffuse into i r o n only when the i r o n c o n t a c t s water d i r e c t l y . This diffusion phenomenon of hydrogen i n c r e a s e d m a r k e d l y with t e m p e r a t u r e and was a c c e l e r a t e d by a b r a s i o n and hydrogen ion c o n c e n t r a t i o n in dilute acid. A b r a s i o n and hydrogen ions in a dilute acidic Buffer solution did not affect the diffusion coefficient of h y d r o g e n , D, but i n c r e a s e d the hydrogen c o n c e n t r a t i o n at the i r o n s u r f a c e contacting water or Buffer solution, Cs. The p e r m e a b i l i t y of hydrogen in f u l l y - a n n e a l e d i r o n in contact with d i s t i l l e d w a t e r and the diffusion coefficient of hydrogen in f u l l y - a n n e a l e d and slightly c o l d - w o r k e d i r o n for the t e m p e r a t u r e r a n g e 10~ to 100~ were m e a s u r e d . T r a p p i n g p a r a m e t e r s in the slightly c o l d - w o r k e d i r o n were calculated.
DIFFUSIONof hydrogen plays
an i m p o r t a n t role in the field of s t r e s s - c o r r o s i o n of m e t a l s . Norton ~ d e m o n s t r a t e d the p o s s i b i l i t y of diffusion of hydrogen through m e t a l in his use of a s t e e l - s h e l l e d i o n i z a t i o n gage to m e a s u r e hydrogen p a r t i a l p r e s s u r e . D a r k e n and Smith 2 d e t e r m i n e d the b e h a v i o r of hydrogen in s t e e l d u r i n g and after i m m e r s i o n in acid by m e a s u r i n g the d i s p l a c e m e n t of butyl phthalate in a c a l i b r a t e d b u r e t t e due to the diffused hydrogen f r o m the acid through and out of a s t e e l disc. They showed the i n c r e a s e of s o l u b i l i t y and p e r m e a b i l i t y of h y d r o g e n in SAE 1020 s t e e l with the d e c r e a s e of pH at 35~ the i n c r e a s e of hydrogen p e r m e a b i l i t y with t e m p e r a t u r e and the i n c r e a s e of hydrogen a b s o r p t i o n with cold r e d u c t i o n . F r a n k , Swets, and F r y 3 used a m a s s s p e c t r o m e t e r and an a b r a s i o n technique to study diffusion of hydrogen in mild s t e e l in contact with w a t e r over the t e m p e r a t u r e range 25~ to 90~ By taking into c o n s i d e r a t i o n the c h a r a c t e r i s tics of the m a s s s p e c t r o m e t e r , they obtained 6.3 kcal p e r mole for the b u i l d - u p (stabilization) t e c h n i q u e . 1 , *In the build-upor stabilizationtechnique,the hydrogenconcentrationbuilds up from roughlyzero to the steady state value. The s a m e a u t h o r s 4 c o n s i d e r e d that c l e a n i r o n was c o n t i n u a l l y p r e s e n t e d to water d u r i n g a b r a s i
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