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Weather resistance of porcelain enamels
64
NATIONAL BUREAU OF STANDARDS NOTES.
[J. F. I.
W E A T H E R RESISTANCE OF PORCELAIN E N A M E L S .
D u r i n g the p a s t few y e a r s the i n c r e a s e d u s e of porcelain-enameled s t e e l as a n a r c h i t e c t u r a l m a t e r i a l h a s a c c e n t u a t e d the need for a d e q u a t e d a t a on the w e a t h e r i n g r e s i s t a n c e of v a r i o u s t y p e s of p o r c e l a i n e n a m e l s . In 1939 the N a t i o n a l B u r e a u of S t a n d a r d s b e g a n a long r a n g e , s y s t e m atic s t u d y of the w e a t h e r r e s i s t a n c e of p o r c e l a i n e n a m e l s . S p e c i m e n s i n c l u d i n g both a c i d - r e s i s t a n t a n d n o n - a c i d - r e s i s t a n t e n a m e l s w e r e supp l i e d by s i x t e e n c o o p e r a t i n g m a n u f a c t u r e r s and e x p o s e d t o f o u r diff e r e n t c l i m a t i c c o n d i t i o n s : t e m p e r a t e residential, t e m p e r a t e i n d u s t r i a l , t e m p e r a t e " s a l t a i r , " a n d s e m i t r o p i c a l r e s i d e n t i a l . F i v e d u p l i c a t e sets of s p e c i m e n s w e r e p r e p a r e d . O n e of t h e s e was p l a c e d in s t o r a g e a n d the o t h e r f o u r i n s t a l l e d a t s e l e c t e d e x p o s u r e s i t e s in W a s h i n g t o n D. C. ; St. L o u i s , Mo. ; A t l a n t i c C i t y , N. J . ; a n d L a k e l a n d , Fla. T h e p a n e l s w e r e i n s t a l l e d in 1940. A t the end of the f i r s t year a c o m p l e t e i n s p e c t i o n was m a d e a n d the r e s u l t s , t o g e t h e r with p r e l i m i n a r y w o r k on a c c e l e r a t e d t e s t s , w e r e p u b l i s h e d a t t h a t t i m e . T h e s e c o n d i n s p e c t i o n of the p a n e l s a t the f o u r locations was d e l a y e d due t o w a r c o n d i t i o n s a n d was not c o m p l e t e d u n t i l 1947 w h e n the p a n e l s had b e e n e x p o s e d for s e v e n y e a r s . T h e more i m p o r t a n t f i n d i n g s m a y be s u m m a r i z e d a s f o l l o w s : In c o n t r a s t t o the r e s u l t s of the first-year inspection, w h i c h s h o w e d m o s t w e a t h e r i n g effects a t St. L o u i s a n d W a s h i n g t o n , the s e v e n - y e a r d a t a i n d i c a t e t h a t the c o n d i t i o n s a t A t l a n t i c City w e r e m o s t s e v e r e on the a c i d - r e s i s t a n t e n a m e l s w h i l e L a k e l a n d c o n d i t i o n s were m o s t s e v e r e on the n o n - a c i d - r e s i s t a n t comp o s i t i o n s . T h e d a t a from the St. L o u i s p a n e l s a t s e v e n y e a r s w e r e not c o n s i s t e n t with the o t h e r d a t a b e c a u s e of a h e a v y , a d h e r e n t , t a r - l i k e d e p o s i t o r i g i n a t i n g from h e a v y s m o k e c o n c e n t r a t i o n in the test a r e a , w h i c h was n e a r a r a i l w a y t e r m i n a l . T h e r e s u l t i n g film was protective, b u t w o u l d not n o r m a l l y have been p e r m i t t e d t o a c c u m u l a t e for a sixyear period. G o o d correlation e x i s t e d b e t w e e n w e a t h e r resistance, a s m e a s u r e d by the a v e r a g e p e r c e n t a g e of the i n i t i a l g l o s s r e t a i n e d , a n d acid resista n c e , a s d e t e r m i n e d by the s t a n d a r d P o r c e l a i n E n a m e l I n s t i t u t e test. N o t i c e a b l e f a d i n g of g l o s s y c o l o r e d e n a m e l s o c c u r r e d only on t h o s e p a n e l s of poor acid r e s i s t a n c e . W h e r e the i n i t i a l c o v e r a g e was comp l e t e a n d no m e c h a n i c a l d a m a g e h a d o c c u r r e d , p r o t e c t i o n of the m e t a l a g a i n s t c o r r o s i o n was u n i m p a i r e d a f t e r s e v e n y e a r s for all s p e c i m e n s .
COMPARISON
OF IONOSPHERIC DATA FROM ANTIPODAL P O I N T S .
F o r s e v e r a l y e a r s it of a s t a t i o n in a g i v e n the y e a r are s i m u l a t e d r e s p o n d i n g s e a s o n . If
h a s been k n o w n t h a t i o n o s p h e r i c c h a r a c t e r i s t i c s l a t i t u d e a n d l o n g i t u d e a n d a t a g i v e n s e a s o n of by a s t a t i o n a t the a n t i p o d a l p o i n t for the corthis reciprocity can be d e f i n i t e l y e s t a b l i s h e d i t
NATIONAL BUREAU OF STANDARDS NOTES.
[J. F. I.
W E A T H E R RESISTANCE OF PORCELAIN E N A M E L S .
D u r i n g the p a s t few y e a r s the i n c r e a s e d u s e of porcelain-enameled s t e e l as a n a r c h i t e c t u r a l m a t e r i a l h a s a c c e n t u a t e d the need for a d e q u a t e d a t a on the w e a t h e r i n g r e s i s t a n c e of v a r i o u s t y p e s of p o r c e l a i n e n a m e l s . In 1939 the N a t i o n a l B u r e a u of S t a n d a r d s b e g a n a long r a n g e , s y s t e m atic s t u d y of the w e a t h e r r e s i s t a n c e of p o r c e l a i n e n a m e l s . S p e c i m e n s i n c l u d i n g both a c i d - r e s i s t a n t a n d n o n - a c i d - r e s i s t a n t e n a m e l s w e r e supp l i e d by s i x t e e n c o o p e r a t i n g m a n u f a c t u r e r s and e x p o s e d t o f o u r diff e r e n t c l i m a t i c c o n d i t i o n s : t e m p e r a t e residential, t e m p e r a t e i n d u s t r i a l , t e m p e r a t e " s a l t a i r , " a n d s e m i t r o p i c a l r e s i d e n t i a l . F i v e d u p l i c a t e sets of s p e c i m e n s w e r e p r e p a r e d . O n e of t h e s e was p l a c e d in s t o r a g e a n d the o t h e r f o u r i n s t a l l e d a t s e l e c t e d e x p o s u r e s i t e s in W a s h i n g t o n D. C. ; St. L o u i s , Mo. ; A t l a n t i c C i t y , N. J . ; a n d L a k e l a n d , Fla. T h e p a n e l s w e r e i n s t a l l e d in 1940. A t the end of the f i r s t year a c o m p l e t e i n s p e c t i o n was m a d e a n d the r e s u l t s , t o g e t h e r with p r e l i m i n a r y w o r k on a c c e l e r a t e d t e s t s , w e r e p u b l i s h e d a t t h a t t i m e . T h e s e c o n d i n s p e c t i o n of the p a n e l s a t the f o u r locations was d e l a y e d due t o w a r c o n d i t i o n s a n d was not c o m p l e t e d u n t i l 1947 w h e n the p a n e l s had b e e n e x p o s e d for s e v e n y e a r s . T h e more i m p o r t a n t f i n d i n g s m a y be s u m m a r i z e d a s f o l l o w s : In c o n t r a s t t o the r e s u l t s of the first-year inspection, w h i c h s h o w e d m o s t w e a t h e r i n g effects a t St. L o u i s a n d W a s h i n g t o n , the s e v e n - y e a r d a t a i n d i c a t e t h a t the c o n d i t i o n s a t A t l a n t i c City w e r e m o s t s e v e r e on the a c i d - r e s i s t a n t e n a m e l s w h i l e L a k e l a n d c o n d i t i o n s were m o s t s e v e r e on the n o n - a c i d - r e s i s t a n t comp o s i t i o n s . T h e d a t a from the St. L o u i s p a n e l s a t s e v e n y e a r s w e r e not c o n s i s t e n t with the o t h e r d a t a b e c a u s e of a h e a v y , a d h e r e n t , t a r - l i k e d e p o s i t o r i g i n a t i n g from h e a v y s m o k e c o n c e n t r a t i o n in the test a r e a , w h i c h was n e a r a r a i l w a y t e r m i n a l . T h e r e s u l t i n g film was protective, b u t w o u l d not n o r m a l l y have been p e r m i t t e d t o a c c u m u l a t e for a sixyear period. G o o d correlation e x i s t e d b e t w e e n w e a t h e r resistance, a s m e a s u r e d by the a v e r a g e p e r c e n t a g e of the i n i t i a l g l o s s r e t a i n e d , a n d acid resista n c e , a s d e t e r m i n e d by the s t a n d a r d P o r c e l a i n E n a m e l I n s t i t u t e test. N o t i c e a b l e f a d i n g of g l o s s y c o l o r e d e n a m e l s o c c u r r e d only on t h o s e p a n e l s of poor acid r e s i s t a n c e . W h e r e the i n i t i a l c o v e r a g e was comp l e t e a n d no m e c h a n i c a l d a m a g e h a d o c c u r r e d , p r o t e c t i o n of the m e t a l a g a i n s t c o r r o s i o n was u n i m p a i r e d a f t e r s e v e n y e a r s for all s p e c i m e n s .
COMPARISON
OF IONOSPHERIC DATA FROM ANTIPODAL P O I N T S .
F o r s e v e r a l y e a r s it of a s t a t i o n in a g i v e n the y e a r are s i m u l a t e d r e s p o n d i n g s e a s o n . If
h a s been k n o w n t h a t i o n o s p h e r i c c h a r a c t e r i s t i c s l a t i t u d e a n d l o n g i t u d e a n d a t a g i v e n s e a s o n of by a s t a t i o n a t the a n t i p o d a l p o i n t for the corthis reciprocity can be d e f i n i t e l y e s t a b l i s h e d i t