Control de corrosion

U. S. Department o f A g r i c u l t u r e S l Department S r v i c e U.o iS. Conservationof eAgriculture Engineering D i v i s i o n Soil Conservation Service Design Branch Engineering Division

February 1, 1971

February 1, 1971

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Design Branch
DESIGN N T NO. OE Subject: 12"

DESIGN NOTE NO, 12* Subject:

Control o f Underground Corrosion

Control of Underground CorrosionBuried m e t a l p i p e s and o t h e r m d e r g r o u n d m e t a l o b j e c t s a r e s u b j e c t t o very r ametal opipes o and other e ~ t a i n o n d i tmetal objectso n s which o c c u r c Buried p i d c r r o s i n under c 1:nderground i o n s , c o n d i t i are subject to c o n s i d e r a l e number o commonly enough t o demand c ceLtain a conditions, A conditions bwhich occur fareful ttention. very rapid corrosion under s t e e l i r r ienough n to i p e s and careful i z e d s t e e l p i p e considerable nnumber of g a t i o p demand g a l v a n attention, A s p i l l w a y c o d u i t s commonly i n s t a irrigation pipes and galvanized steel c o r spillway conduits steel l l e d with SCS a s s i s t a n c e have f a i l e d by pipe r o s i o n a f t e r o n l y a few y ea r s s e r i c e installed ' with v SCS . assistance have failed by corrosion after only a The purpose o f t h i s d e s i g n n o t e i s t o p r o v i d e i n t e r i m guidance i n c a r purpose t this design note Engineering interim guidance The r y i n g o u t ofh e requirements o f is to provide Standard 432-F and in Engineering Memorandum-27 p e r t a i n i n g t o c o r r o Standardt432-F A t e c h n i c a l carrying out the requirements of Engineering s i o n c o n r o l . and r e l e a s e on t h e g e n e r a l t o p i c of underground c o r r o s i o n w i l l b e i s s u e d Engineering Memorandum-27 pertaining to corrosion control. A technical l a t e r i f on t the general b topic of underground corrosion will be issued release i proves t o e needed.

few years'service.

later if it proves to be needed. Engineering Standard 432-F a p p l i e s t o s t e e l i r r i g a t i o n p i p e l i n e s .
Engineering Engineering Memorandum-27 covers t h e u steel g a l v a n i z e d pipelines. welded Standard 432-F applies to s e of irrigation s t e e l and s t e e l p i p e i n e a r t h dams. The d i s c u s s i o n t h a t f o l l o w s i s d i r e c t e dEngineering Memorandum-27 covers the use of galvanized steel and welded toward t h e e i n d s f p i p i n s steel pipe s in k earth odams. e The t a l l a t i o n s . that follows is o directed discussion However, most f i t i s e q u a l l y a p p l i c a b l e t o any underground o r p a r t i y underground s t e e l toward these kinds of pipe installations. However, most of it is structure. equallyapplicable to any underground or partly underground steel structure.

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Aluminum They a r e Aluminum apply t o They are those of

apply to their protection, but the properties of aluminum differ from those of steel in several important ways: (1) A n a t u r a l o x i d e forms i n m e d i a t e l y upon exposure o f (1) A natural oxide forms immediately upon exposure of s u b s t a n t i a lp r o t e c t i o n a g a i n s t c o r r o s i o n i n most a'ly aluminum surface to the atmosphere, which provides environments . substantial protection against corrosion in most enviromnents.
m y alt~rnin~imu r f a c e t o t h e atmosphere, which p r o v i d e s s

a l l o y p i p e s and s t r u c t u r e s a r e n o t s p e c i f i c a l l y i n c l u d e d . s u b j e c t t o s i m i l ar c o r r o s i o n p r o c e s s e s , and t h e same p r i n c i p l e s alloy pipes and structures are not specifically included, t h e i r p r o t e c t i o n , b u t t h e p r o p e r t i e s o f aluminum d i f f e r from subject to similar corrosion processes, and the same principles s t e e l i n s e v e r a l important ways:

(2)

(2)

(3)

oxide film is broken by preventing...