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Coa tings eanProteet a substrate by Providing a barrierbetweenthem etal and i ts environmentand加rthroughthepresenee of eorrosioninhibitors. In orderf or a eoating toPro- vide adeq uate eorrosionProteetion, t h eeo a t i n g m us t b eun if o r m , w e l l a dh ere d , P ore f r eean d se l f -h ea l i n g f o ra PP li ea ti ons w h ere P h y s ie a ld a m a g e t o th eeoa t - i n g m a y oeeur . O neo f t h e P ro bl e m s wi t hm a g nes iu m an d i t sa ll o y s 1 5 i t se h e m i ea l reae ti v i ty . A ssoonas it co m es i ncon t aC twit h a i ror w a t eranox id e / h y d rox id e l盯erf o rms onthe surf aeewhieheax iha ve a detrim en- ta l ef f eeton eoatingadhesion andunif ormity.Up ti ll now , t h ere h a v e b eenanu mb ero f P oss ible eoa ting t ee h no l o g ie s a v a ila bl e f o r m a g n e s i u m an d i t sa l l o y s , wi thth e i r i n d ivid u a l a d v a n t眼esand disadvant铭es 1. Condueting Polym ers as Promisingmaterials , es P e - e i a l ly p o ly伴rrole , i neorros i on p ro t ee t i on a r es t u d i e d onsue h as i r on , s t ee l , AI , Ti , an dz n 11一1 7 1d ue t o i t s h i g h s t a b ili t yin a ir , a dh es i onan d i n t eres t i n g re d o x P ro P er t ie s wi th su b s t r a t e , b u tt h ere 1 5 l essr eseare h e a r r ie d ou t on m a“n e siu m a n d its a llo v sli s , 19 . R e- eently, T r uon g e t a l . 12 0 h a v es tu ( li e d t h eeorros io n t P r o f . , Ph . D . , t o wh o m eor r es P on d ene es h ou l db ea dd r e ss e d , E 一 m a il :son g r g回 16 3 .eo m . P roteetio no f a na ery lie Paint eo ntainin gP o ly P y rro le f i lm o n m agn e siu ma l loybyc h e miea lm etho d , b u tt h e f il m w asnon 一 un if o r m an d P oora d h es i ve . Th ere f o re , i t 1 5neeessar yt o d eve l o P nove l or g a n i e eo a t i n g s f o r m a g - nes i u m an dit sa l l o y s . I n thi sno t e , N a f i on / p o ly那rrole and Naf ion/Dimethysul f oxid (DMSO) orga n ie eoat- ings onmagnesiumha v e beenPreParedb y simPleim- m ersion and heat treatment , an d i t seorros i onres i s - t aneean dm or Ph o l o gi es h a v e b een a l sos t u di e d . T h e b ase m e t a l use d i n t h is s t u d y1 5 i n - d us t r ialP ure m a g nes i u m s h eet . Th eeon t e n t o f N a f i on / p o ly py r ro l eso l u ti on w a s s % p o ly py rro l e b y w e i g h t , w h il e N a f i on / D M SO so l u ti on w as 5 p ar t so f N a f i one t h ano l so l u ti on ( 5 % b yw e i g h t ) t o 1p a r t o f D M SOb y vo l u m e . T h e m a g nes iu m s a m Pl es w er e P o l - ish e d us i n g S ICp a p ers wi th a g r i t s i ze f r o m 40 0 t o 1 000 , an d t h en w e ree l eane d w ith aee t one P r io r t o p re p ar i n gt h eor g an i eeoa t i n g s . T h eeoa t i n g s w e r e f o r m e d a f t er im m ers i on i n t h e N a f i on / p o ly py r ro l eor N a f i on / D M SO so l u tio n f o r 10 5 , an dd r i e d i n a n e le e - t r i e f u rnaee im m e d ia t e ly a t 373 K f o r 5m i nora t 42 3Kf o r 2 h . Th esa m P l es wi t hdi f f e ren t eoa t i n g t h i e k ness w ereo b ta i n e db yint er m e d iat e d r yi n g an d r eeoa ti n g severa l tim es . T h eeoa t i n g m a s s w a s m e a s ure db y e l ee t ron i e b a l - anee wi t h anaeeurae y o f0 . 0 1 m g . Th esur f a ee d ens i ty o f t h eeoa ti n gw asuse d t o d en o t e t h eeoa t i n gthie卜 neSS. P otentiodynam iePolariz就ionm easu rements w e re earriedout f o r both un eo atedandeoatedsPeeimen s, w hi e hw ere P er f o r m e d wi t h aeonven t i ona l th r ee - e l ee t ro d eee lli na mb ie n tt e m P era t ure . A P I歌inum sheetanda satura tedealomeleleetrode (S C E) were u sedas eounter andref eren ee eleetrode,res P ee t i ve ly . T h ee l eetro ly tiet es t so l u tio neon t a i ne ds % N a CI a t a p H o f 11 . T h e a r eao f th e w or k ing e l ee t ro d esu r f a ee w as 1 . 039 e m Z in s i zean d 11 . 55 mm i n d i a m e t er . T h e sur f a eeo f t h euneoa t e d s p ee im en w as g roun db y a s iC p a p ers wi t h a g r i t s i zeo f 1 000 . Th e p o t en t i o d y n a m ie , V o l . 23N o . 1 , 2007 Thbl e 1 Thi e k nessesan d eo rro s i on p r o p er t i eso f uneoa t e d an d eoa t e d m a g nes i u m s p ee i niens S P ee i m en S o l u t i on Imm e r s i on t i m es H ea tt rea t m en t Thi e k ness /( mg / e m Z ) C orros i on ra t e C o rro s i oneu rr en t / h /( mm / y e a r ) 6 56 12 8 0 93 5 3 4 5 8 曰. l q山 一.上 q白nU o n q 月吮 aC J,1,翻 q 白q 乙q 乙q 4 0口 n曰n U C 曰 U 1 1n U C U 一 0 N af io n /p o ly p y r r ole l N a f i o n / poly p yr r ole Z N a f i o n / poly p yr r ole 3 N a f i o n /D M S O I N a f i o n / D M S OZ N af io n / D M S O3 3 7 3 3 7 3 3 7 3 4 2 3 4 2 3 4 2 3 /m A 0 . 0 8 8 7 0 . 14 0 2 0 . 0 8 4 5 0 . 1 26 2 0 . 0181 0 . 0 149 0 . 0 0 4 8 A B C D E F G Fig . 1 M o rp h o log ie s ofu n e o ate d a n d e o atedorg a n ie e o atin g B ef or ee orr o sio n: ( a ) u n e o a t ed , ( e ) n a f i on / p o ly可rrole (d)na f i on/poly讨rrole, ( f ) na f i on / D M SO 5on m a g nes i u mb e f o rean d a f t ereor ros io n tests . ( e ) na f i on / D M SO ; a f t e r eorros i on : ( b ) uneoa t e d , P o la r i za ti onseann i n g s w e res t ar t e da t 一0 .2 5V re l- ativ e tothe rest Potentialwhiehw a s d ete rm in ed at f i rst . T h ese a n rate w a s d e f i n eda s 0 .2 mV / s,an d t h ea b or t er i t er i a w asaeur ren thi gh er t h an 10 mA . O n ly th ee a t h o d ie b rane h o f t h eeurves w asuse df o r t h e d e t er m i n a t i ono f th eeorr os i oneurren t s b y ana l - y s i so f t h e T a f el s l o P e a n df o r th eeorros io nra t eea l - eu l a t io n . Th us , t h ee f f e e t so f t h e a n o d i e d i sso l u tio n l ea d i n gt oan imP ro P er Ihf el e q U a t i ona PP roae h eou l d b ene g l ee t e d . T h e f i t ti n g o f a l lThf el eurves t oo k P l aee in m ar gi nso f 一15 0 mV to一50 mV re lativ etoth e rest Potentialin o rde r toget eo m Pa rab le re sults . T h e m o rP h o log ie sb ef orea n d a f t er eo rro sio n w ere ex amin ed u singanoP tie al m ie ro se oPe , T h e t h i e k nessesan d eorros i on P ro P er ti eso f un - eoa t e d an d eoa t e d or g an i eeoa ti n g s m a g nes i u m s P ee - i m ensare li s t e d i n T a bl e 1 . It1 5 i n d i e a t e d t h a t t h e t h i e k nesso fN a f i on / p o l ypy rro l eor g an i eeoa ti n g a lm os t d oesno t c h an g e wi t h t h e i mm ers i on ti m es , w h ere a s t h e t h i e k nesso fN a f i on / D M SO or g an i eeoa t - i n gi nereases l i ne a r ly wi thth e im m ers i on tim es . Th e corros io nra t ean d eorr os i oneurren t o f t h es P ee i - m enseoa t e dN a f i on / p o ly py r ro l eor g an i eeo a t ing s i n - erease d eo m P are d wit h t h os eo f th euneo a t e d s P ee - im en , 乞 .e., t h e N 版on/polypyrrol e organie eoa tings eannot Proteet ma g nesium f romeorrosionwhilePro- m oting m agnesium tobe eorroded.However , th eeor - r os i onr a t ean d eorros i oneurren t o f t h es P ee im ens eoa t e dN a f i on / D M SO or g an ie eoa t i n g s d eerease dd r a - m a ti ea l ly eo m P are d wi t h th oseo f t h euneoa t e d s P ee i - m en , 艺 .e., t h e N a f i on / D M SO or g an ie eoa t i n g e a n p ro - t ee t m a g nes i u mf r o m eorros io ne f f e e t i ve l y . F i g ure 1 s h o w s t h e m or P h o l o gi eso f uneoate d an d eoa t e dm a g nes i u m s a m P l es b e f o rean d a f t ereorros io n t es t s . Th ereex i s t e d a l o t o f ser a t e h eson t h esur - f a eeo f uneoa t e d s P ee im en , w h il e m os t o f sera t e h es dis a PP e a r e d a f t ereor ros i on a n dm a n y eorros io n h o le s a Pp eare d , w h iehi n d ie a t e d t h a tt h e ma t er i a l w a s eor - ro d e d v e r y ser i ous l y ( see Fi g . 1 ( a ) an d ( b ) . Tll e N a f i on / P o ly py rro l eor g an i eeoa ti n g e x hibit e dd i seon - ti nuouse h arae ter i s ti es , b u tt h eor i gi na l e h arae te r is - ti es d i s a PP eare d eo m P l e t e ly an d a l o t o fd ee P eorro - s i on h o le s a P p e a r e d a f t ereorr os i on t es t ( see Fi g . 1 ( e ) a n d ( d ) . C o m p ar ing F i g . 1 ( d ) wi t h Fi g . 1 ( b ) , i ti seas y t o f i n d t h a t t h es p ee im eneoa t e dN a f i on / p o ly py r ro l e or g an i eeoa ti n g eorr o d e dm oreser i ous th a j n uneoa te d s P ee im en . Th ereason m a y b e t h a t aeon t i nuot一 s N a f i o n / p o ly p y r r o le o rga n ie e o a t ingw a sn o t f o r m e d o n the s u r f a e eo fm a g n e siu m . In a d ditio n , P o ly Py r - ro l e 1 5e le e t r i ea l ly eon d ue ti n gp o l y m eran df o r m e d m i eroee l l wi th m a g nes iu m , t h us P ro m o ti n g eorr o - s i on . It s h ou l db e P o i n t e d ou tth a t ourresu lt 15 no t eons ist en twi t h so m ereseare h er s,res u l ts 1 9 , 20 , b u t i t15 eons i s t en t with o t h errese a r e h ersr es u ltl2 1 , 22 1 . Th i s f a e t su g g es t e d t h a tt h e p ro t ee ti on m ee h a , n i s m s o f eon d ue ti n gP o l y m ersareeo m P l ex a n d eon t ra d i e - 战er.Sei.及ehnol. , V61 . 23N o . 1 , 2007 t o r y i ns o m ee a s es . The r e f o r e , f u r t h er in v es ti g a - tio nsarenee d e d t o e la ri f y t h i s P h e n o m eno n . I n eon t r a s tt o t h e N 硫on/poly即rrol e orga n ie eoa ting , t h e N a f i on / D M SO or g a n i eeo a t i n g e x h ibi t e d eo n t i n - uouse h arae t er i s t i esan d i tw a s se m i t rans p are n t ( see F i g . 1 ( e ) . C o m p ar i n g F i g . 1 ( f ) wi t hF ig . 1 ( d ) , i t ean b eseen th就f ewer eorrosionholesweref o rmedon the su rf aee ofthe N a f i on /DM SO org a n ie eoa tings a f t er eorrosion.T hem orPholog iea lobservation suggested tha tthe eontinuou sN a f i on /DM S O organie eoa t ings ea n a c t a s a ba r rier eoa t ing a nd Proteetm a g nesium f r omeorrosionef f eetiv e l y , w h i e h w aseons ist en twi t h t h eres u l t so f eorros i o n r 就em easu reme毗5. 171S . M a thieu , C . R ap i n , J . H az a na n dP . S tein m etz: r o s . S c i ., 2002 , 44 , 27 37 . G . S o n g , A . A t rens , D . S t j o h n , J . Na i r n a n dY . Li : r o s . S c i ., 1997 , 39 , 85 5 G . S on g , A . A t r ens a n d M . D a r g us e h : Cb r roS . 1999 , 4 1 , 24 9 . Sd ,. .J,. . .J, . . J,. . .J,J. . ., .J. ., . .J., , . .J ; In ,上 ,曰 八J月, 民UO DQ 日L七仁卜州 R E F E R E N C E S 司 刃 s j . 1 , 1j . i r . .r . . . . . . . .L . . . . J , e e J, . J. . , . . J O口 n ,l q自 ,土今山,一勺山 r. . . L 护. .尸. . . . r . . . . 【 1J E.Gr叮 a n d B . Luan:J . A l l妙 C o opd. , 2002 , 336 , 8 8 . 【 2 B . L.Mordike and T . Ebert:Ma亡 er. S Cj. E ng . A , 2001 , 302 , 37 . 3G . L.Songand A . Atrens:A dy.E刀9 . M a亡er., 2003 , 5 , 8 37 . 【 4E.G ha li , W . Di et z e l an dK . U . Ka i ner : J . M直te r . 血9. 尸er丘理田 , 2004 , 13 , 7 . 【 5R G . S on g , C Bl a w e r t , W . Diet ze l an dA . A tr ens : M 执te r . S c主 . E 刀g . A , 2005 , 399 , 3 08 . 6F . Czerw inski:Ae亡 a M五亡e r ., 2002 , 50 , 2