Nâng cao khả năng chống ăn mòn của lớp phủ hữu cơ trên nền thép được biến tính bằng Zr, Ti

Header Page of 145 B GIO DC V O TO I HC NNG BO CO TểM TT TI KHOA HC V CễNG NGH CP I HC NNG TI: NNG CAO KH NNG CHNG N MềN CA LP PH HU C TRấN NN THẫP C BIN TNH BNG Zr, Ti M S: 2015-02-116 CH NHIM TI: PGS.TS Lấ MINH C Nng, thỏng nm 2016 Footer Page of 145 Header Page of 145 MC LC CHNG 1: TNG QUAN Lí THUYT 1.1 Tng quan v n mũn v bo v kim loi 1.2 Cỏc phng phỏp bo v kim loi 1.2.1 Loi b cỏc cu t gõy n mũn kim loi 1.2.2 Nõng cao bn chng n mũn kim loi bng cỏc lp ph 1.2.3 Bo v kim loi chng n mũn kim loi bng phng phỏp in hoỏ 1.2.4 Th ng kim loi 1.3 Lp ph hu c 1.4 Lp bin tớnh trờn b mt kim loi 1.5 Lp bin tớnh b mt kim loi cha Zr, Ti CHNG 2: THC NGHIM 2.1 Cỏc phng phỏp nghiờn cu 2.1.1 Kớnh hin vi in t quột (SEM) 2.1.2 Ph tỏn x nng lng tia X 2.1.3 Phng phỏp ph hunh quang tia X (XRF) 2.1.4 Phng phỏp o Ph tng tr in húa 2.2 Húa cht, thit b, dng c thớ nghim 11 2.2.1 Húa cht 11 2.2.2 Thit b nghiờn cu 12 2.2.3 Chun b dung dch, mu thộp 12 CHNG 3: KT QU V THO LUN 13 3.1 Nghiờn cu phõn cc ca thộp theo pH 13 3.2 ng cong phõn cc ca mng bin tớnh 16 3.3 Tớnh cht b mt ca lp ph (ti im ti u) 17 3.3.1 S to thnh lp bin tớnh 17 3.3.2 Cu trỳc t vi 18 3.4 Mng epoxy trờn nn thộp bin tớnh 19 3.4.1 Tng tr in húa 19 3.4.2 ỏnh giỏ kh nng bo v ca mng 21 i Footer Page of 145 Header Page of 145 KT LUN 23 DANH MC BIU BNG, HèNH V Hỡnh 1-1 ng cong Tafel xỏc nh dũng v th n mũn Hỡnh 1-2 Bo v kim loi bng phng phỏp ỏp dũng in ngoi 1: Kt cu cn bo v; 2:mụi trng dn in; 3:Vt liu lm anode; 4:ngun in chiu; 5: bin tr Hỡnh 1-3 S nguyờn lý bo v bng anode hy sinh 1: kim loi cn bo v; 2:anode hy sinh; Cht bc anode hy sinh; 4:ng h o in; 5:ngun in Hỡnh 1-4: C ch búc tỏch lp mng hu c trờn nn kim loi nn kim loi b n mũn Hỡnh 2-1: Mch tng ng vi phn ng in cc n Re: in tr dung dch; Rct: in tr chuyn in tớch; Cdl: in dung lp in tớch kộp 10 Hỡnh 2-2 : Biu din tng tr ca phn ng n theo kiu Nyquist 10 Hỡnh 2-3: Biu din tng tr theo kiu gin Bode 11 Hỡnh 3-1 ng cong phõn cc ca thộp dung dch 0,01 M ZrF 62- thay i pH 1)pH=2; 2)pH=4; 3)pH=6 Tc quột th 10mV/s 13 Hỡnh 3-2 ng cong Tafel ca thộp dung dch cha TiF62-,ZrF62- vi cỏc giỏ tr nng TiF62- khỏc 1)0,02 ; 2) 0,04; 3) 0,06 M, pH =5 Tc quột 10mV/s 14 Hỡnh 3-3 S thay i th ngh OCP ca Fe cỏc dung dch: 1)dung dch th ng cha Zr, Ti ti u, 2) dung dch TiF62- 0,02M , 3)KCl 3% 15 Hỡnh 3-4 ng cong Tafel ca 1)thộp; 2)thộp c bin tớnh dung dch Zr Ti; 3) Thộp c bin tớnh CrO42- 0,1M Dung dch o KCl 3%, tc quột 10mV/s 16 Hỡnh 3-4 S thay i tớnh cht b mt ca in cc thộp trc(1) v sau (2) bin tớnh dung dch ZrTi Ph o dung dch H2SO4 10% 17 Hỡnh 3-5 S mch in tng ng ca b mt thộp 17 ii Footer Page of 145 Header Page of 145 Hỡnh 3-6 Cu trỳc t vi v thnh phn nguyờn t ca b mt Fe (a) trc v (b) sau bin tớnh dung dch cha Zr, Ti 18 Hỡnh 3-7 S mch in tng ng ca h epoxy/thộp bin tớnh 20 Hỡnh 3-8 Ph tng tr in húa ca mng epoxy trờn nn thộp cha bin tớnh Ph thu c KCl 3% Thi gian ch o mu 60 phỳt 20 Hỡnh 3-9 Ph tng tr in húa ca mng epoxy trờn nn thộp ó c bin tớnh dung dch ZrTi Ph thu c KCl 3% Thi gian ch o mu 60 phỳt 21 Hỡnh 3-10 Hỡnh nh b mt mu thộp c ph mng epoxy cú (a) v khụng cú (b) lp x lý bng bin tớnh dung dch ZrTi 22 Hỡnh 3-11 Hỡnh nh phỏ hy mng epoxy trờn nn thộp a)nn thộp c th ng dung dch Cr, b)nn thộp th ng dung dch ZrTi, c) thộp nn khụng cú lp bin tớnh Thi gian ngõm mu gi 23 iii Footer Page of 145 Header Page of 145 Footer Page of 145 Header Page of 145 RESULT INFORMATION OF PROJECT General information Project title: Improving the corrosion protection of organic coating with conversion layer containing Ti Zr Code number: 2015-02-116 Project leader: Assoc Prof Dr Le Minh Duc Coordinator: Nguyen Thi Huong, Duong Thi Hong Phan Implementing institution: The University of Danang Duration: From Sep 2015 to Sep 2016 Objectives - Fabrication of conversion layer consisted of Ti, Zr chemically - Conversion layer improve the corrosion protection of organic coating Creativeness and innovativeness - Forming of conversion layer with Ti, Zr chemically - Enhancing the protection ability of epoxy coating Research results - Studying the conversion solution containing Zr, Ti - Characterisation of material with SEM, EIS, EDX and Open Circuit Potential; - Ti, Zr of conversion layer can improve the corrosion protection of organic coating Products - Sample of steel with conversion layer Effects, transfer alternative of research results and applicability - High ability to transfer the technique to industry for corrosion protection of metal v Footer Page of 145 Header Page of 145 M U Kim loi luụn l vt liu c la chn u tiờn nhiu lnh vc ca i sng ngi cú bn cao so vi g, thy tinh, composite d to hỡnh theo yờu cu, cú th to nờn cỏc cụng trỡnh cú tui th hng th k! Tuy vy cỏc mụi trng m t, cú nhiu hi mui nh khu vc bin thỡ kim loi d b n n mũn, gim bn ca cụng trỡnh, cu kin, thit b Hin cú nhiu phng phỏp bo v, chng n mũn kim loi nh: Bo v cathode (anode hy sinh, phõn cc bng dũng in ngoi); to lp ph hu c nhm ngn cỏch kim loi v mụi trng n mũn; to lp ph th ng lm lp lút Mi phng phỏp u cú u nhc im, kh nng ỏp dng tựy thuc vo iu kin thc t Phng phỏp to lp ph bin tớnh l mt phng phỏp ph bin c s dng, mang li hiu qu cao, r tin Phng phỏp pht phỏt húa b mt kim loi ó c s dng ph bin hin Lp bin tớnh ny xp, cú kh nng to lp nn cho cỏc lp ph hu c rt tt To lp ph bin tớnh nõng cao kh nng chng n mũn ca lp ph hu c bng vi cỏc nguyờn t Mo, Ti, Zr thu hỳt nhiu s quan tõm, nghiờn cu Mc tiờu ti: Bng phng phỏp húa hc, lp ph cha Ti, Zr c to trờn b mt thộp nhm ci thin, tng cng kh nng bo v kim loi ca cỏc lp ph hu c Phng phỏp nghiờn cu: Cỏc k thut in húa thụng dng s dng: phõn cc in húa xõy dng ng cong Tafel v d oỏn tc n mũn Cu trỳc t vi ca b mt c xỏc nh bng kớnh hin vi in t quột (SEM); cng nh EDX nhm xỏc nh s cú mt cỏc nguyờn t Ti Zr ỏnh giỏ kh nng chng n mũn ca lp ph qua phộp o ph tng tr in húa, o ng cong Tafel T õy cú kt lun v nh hng ca Ti, Zr ci thin kh nng chng n mũn nn thộp vi Footer Page of 145 Header Page of 145 i tng v phm vi nghiờn cu: Ti, Zr c s dng dng mui hoc acid trng thỏi dung dch Thộp thng c nhỳng chỡm vo dung dch hỡnh thnh lp th ng Mng nha epoxy c ph lờn nn thộp ó c to lp bin tớnh v mc ci thin chng n mũn ca mng c nghiờn cu, ỏnh giỏ Ni dung nghiờn cu: - Nghiờn cu to lp bin tớnh bng phng phỏp húa hc: chun b dung dch, tỡm iu kin ti u vi cỏc thnh phn Ti, Zr dung dch cho kh nng chng n mũn cao nht ỏnh giỏ qua th, dũng n mũn mụi trng n mũn - Xỏc nh thnh phn húa hc, cu trỳc t vi ca mng lp ph bin tớnh, bn cht ca lp bin tớnh bng phng phỏp o ph nh EDX, XRF, SEM - To lp ph epoxy trờn nn thộp ó bin tớnh v ỏnh giỏ kh nng bo v ca mng vii Footer Page of 145 Header Page of 145 CHNG 1: TNG QUAN Lí THUYT 1.1 Tng quan v n mũn v bo v kim loi Vn n mũn kim loi cú liờn quan n hu ht cỏc ngnh kinh t Ngi ta ó tớnh c rng giỏ tin chi phớ cho lnh vc n mũn chim khong 4% tng thu nhp quc dõn i vi nhng nc cú nn cụng nghip phỏt trin [1] V bn cht húa hc, phn ng n mũn thng cú bn cht l cỏc phn ng in húa, xy trờn cỏc in cc anode v cathode Phn ng xy trờn in cc cú th l oxi húa hoc kh Cht oxi húa O di chuyn n b mt in cc nhn eletron tr thnh cht kh R, phn ng c biu din: O + ne- R Phn ng oxy húa cú th l phn ng hũa tan in cc kim loi M Mn+ +neTheo quy c, cỏc phn ng in cc l cỏc na phn ng Mi na phn ng gn lin vi mt giỏ tr th in cc tiờu chun E 0, c o so vi in cc tiờu chun hydro (Standard Hydrogen Electrode) hot cỏc cu t bng n v Vi na phn ng cõn bng, in th E, liờn h vi th in cc tiờu chun E0 qua phng trỡnh Nernst E E0 RT i ln nF i l h s t lng phng trỡnh phn ng, l hot cu t i Thng s dng nng thay cho hot vi a i= i.Ci, i l h s hot ca cu t i Phng trỡnh Nernst c vit li E E 0' RT i ln Ci nF E0 gi l th in cc thc t (th iu kin), ph thuc vo mụi trng Mi liờn h th in cc, hng s tc phn ng in cc th hin qua kc k0 exp c n.F.(E E 0' ) / RT vi phn ng kh Footer Page of 145 Header Page 10 of 145 ka k0 exp a n.F.(E E 0' ) / RT vi phn ng oxi húa Trong phng trỡnh ny, c, a l h s chuyn in tớch ca phn ng cathode v anode, th hin s i xng ca hng ro hot húa Vi cỏc phn ng trờn in cc kim loi, phn ng n gin, cú giỏ tr bng 0,5 cho c hai na phn ng Mt dũng quan sỏt c ti mt giỏ tr th E s l I= Ic + Ia nF n.F I nF k C R exp( a E ) k C o exp( c E ) RT RT Quỏ th = E- Eeq Quỏ th o s chờnh lch th thc nghim vi th cõn bng dung dch nghiờn cu Khi E=Eeq, biu thc trờn tr thnh I nFk0 C R exp( a nF RT Eeq ) nFk0 C0 exp( c n.F Eeq ) RT Thay giỏ tr I0 vo phng trỡnh trờn ta c phng trỡnh Butler Volmer nF n.F I I exp( a ) exp( c ) RT RT Khi phõn cc õm Ic>>Ia, nhúm th phng trỡnh xp x bng 0, phng trỡnh tr thnh n.F I I exp( c ) RT Phng trỡnh ny cú th ỏp dng quỏ th ln hn 52mV, cho thy rng, khong th ny, dũng in tng theo quy lut exponen vi quỏ th Ly logarith hay v log( I ) log I c n.F 2.3.RT õy l phng trỡnh Tafel cho nhỏnh cathode Hon ton tng t, Ia>>Ic ta c phng trỡnh Tafel cho nhỏnh anode log( I ) log I Footer Page 10 of 145 a n.F 2.3.RT Header Page 20 of 145 2.2.2 Thit b nghiờn cu Tng tr in húa thu c trờn mỏy tng tr Zahner (Zenium) Workstation (CHLB c) Thớ nghim c thc hin ti Phũng Thớ nghim Húa lý-Trng i hc S phm H Ni Mỏy o cu trỳc t vi b mt: SEM v EDX (trờn thit b SEM-Hitachi-4800) Cỏc phộp o phõn tớch XRF xỏc nh thnh phn kim loi nn, lp bin tớnh c thc hin ti Trung tõm phõn tớch phõn loi Xut nhp khu, chi nhỏnh ti Min Trung Cỏc phộp o in húa c thc hin trờn mỏy in húa a nng PGS-HH10 (Vit Nam) ti Phũng thớ nghim in húa Trng i hc Bỏch khoa, H Nng Cỏc phộp o in húa c thc hin trờn bỡnh o in cc in cc so sỏnh l Ag/AgCl, in cc i l thộp khụng g) 2.2.3 Chun b dung dch, mu thộp Theo cỏc ti liu tham kho v kho sỏt s b, nng ZrF62- bng 0,01M cho giỏ tr dũng n mũn v th n mũn ca thộp l thp nht [18] Giỏ tr ny c trỡ tt c cỏc thớ nghim; hm lng TiF62- c tớnh toỏn, b sung vo vi cỏc nng 0,02M, 0,04M v 0,06M t axit H2TiF6 Dung dch bin tớnh cha ZrF62- v TiF62- (ZrTiF) c chun b t cỏc axớt tng ng, pH ca dung dch c iu chnh tng dn t 2, n bng dung dch NaOH 20% Thi gian bin tớnh mu thộp t 1-2 phỳt Mu thộp thng c chun b vi kớch thc 5cm x 3cm x 0,8 mm hoc 1cm x 2,5cm x 0,8 mm tựy thuc thớ nghim (o tng tr, ng cong phõn cc, phõn tớch hỡnh nh cu trỳc t vi ) Mu c c mi c hc bng cỏc loi giy nhỏm ln lt P-600, P-800 ri P-1000, c sch dũng nc chy ri ngõm vo dung dch ty du m NaOH 20% Mu c sch v bo qun ethanol ch cỏc phộp o tip theo Mng epoxy c ph theo phng phỏp quột tay 12 Footer Page 20 of 145 Header Page 21 of 145 CHNG 3: KT QU V THO LUN 3.1 Nghiờn cu phõn cc ca thộp theo pH ng cong Tafel thu c cỏc dung dch cú pH khỏc c th hin trờn hỡnh Hỡnh 3-1 0.02 Dòng điện (mA) 0.002 2E-4 2E-5 2E-6 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 Thế điện cực (V/ Ag/AgCl) Hỡnh 3-1 ng cong phõn cc ca thộp dung dch 0,01 M ZrF62- thay i pH 1)pH=2; 2)pH=4; 3)pH=6 Tc quột th 10mV/s Trờn Hỡnh 3-1, cú th nhn thy rng tng dn giỏ tr pH t n 4, dũng n mũn cú xu hng gim nhanh chúng Th n mũn dch chuyn dn sang phớa dng hn Tip tc tng pH, dũng n mũn li tng, th n mũn li dch chuyn v phớa õm hn Trong dung dch pH=4, dũng n mũn ca thộp l nh nht T ng cong Tafel, bng phng phỏp ngoi suy, ta cú th xỏc nh dũng v th n mũn Trong cỏc mụi trng, phn ng cú th xy nh sau: + Phn ng anode l phn ng hũa tan Fe Fe = Fe2+ + 2e + Phn ng cathode l cỏc phn ng gii phúng H2, kh O2 xy ng thi trờn cathode tựy thuc mụi trng O2 + H2O + 4e = OH- 2H+ + e + H2 13 Footer Page 21 of 145 Header Page 22 of 145 Khi tng pH cú s thy phõn ca ZrF62-, to nờn cỏc kt ta oxide (ZrO2.2H2O) pH tng s to thun li cho vic hỡnh thnh lp ph bin tớnh trờn cỏc vựng cathode t vi ca mu thộp ZrF62- + 4OH- = ZrO2.2H2O + 6Fiu ny cú th gii thớch rng, ti pH thp hn, Fe hũa tan nhiu, phn ng cathode thun li hn lng electron cung cp nhiu hn, dn n pH cc b tng cao Tuy vy, tip tc tng pH, cỏc sn phm n mũn khụng tan cú th c kt ta Ngc li pH thp, mng b hũa tan tr li dung dch, mng khụng th bo v kim loi nn lõu hn na Cú nhiu Fe2+ dung dch, cú s cnh tranh kt ta gia Zr v Fe Khi pH tng cao, quỏ trỡnh thy phõn xy mnh, cú th quan sỏt c Zr v Ti kt ta dng oxit dung dch, lm gim nng ZrF62- v TiF62- dung dch Vic hỡnh thnh mng trờn b mt st b nh hng iu ny to dn n mng bin tớnh dung dch pH=4 tt hn pH=2 v Nh vy, vi dung dch cú pH=4, cho thy Fe ó hon ton b th ng dung dch ny [18] thy rừ nh hng ca thnh phn TiF62-, dung dch vi thnh phn nh trờn v thờm vo lng TiF62- ln lt l 0,02M ; 0,04M v 0,06 M Cỏc ng cong phõn cc Tafel ghi li c v th hin trờn Hỡnh 3-2 Mật đồng dòng điện (mA/cm ) 0.1 0.01 1E-3 1E-4 1E-5 1E-6 1E-7 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 Thế điện cực (V/ Ag/AgCl) Hỡnh 3-2 ng cong Tafel ca thộp dung dch cha TiF62-,ZrF62- vi cỏc giỏ tr nng TiF62- khỏc 1)0,02 ; 2) 0,04; 3) 0,06 M, pH =5 Tc quột 10mV/s 14 Footer Page 22 of 145 Header Page 23 of 145 Trờn Hỡnh 3-2 l s thay i dũng v th n mũn thờm TiF62- vi cỏc nng khỏc nhau, gi khụng i pH dung dch bng Vi nng TiF62bng 0,02M cho ta dũng n mũn l nh nht, th n mũn dng nht Thộp nn kim loi ó ri vo trng thỏi th ng Khi b sung nng TiF62- vi nng ln hn, cú th quan sỏt s kt tinh tr li ca cỏc mui Ti v Zr Do vy nng ca Zr v Ti dung dch s gim, lm nh hng n cht lng lp ph bin tớnh õy cng l lý quan trng cho s thay i dũng n mũn v th n mũn ca thộp Nh vy, dung dch th ng ti u s l: ZrF62- 0,01M, TiF62- 0,02M, pH=4, thi gian nhỳng mu to mng l phỳt -0.1 Thế điện cực V (Ag/AgCl) -0.2 -0.3 -0.4 -0.5 -0.6 -0.7 200 400 600 800 1000 Thời gian (giây) Hỡnh 3-3 S thay i th ngh OCP ca Fe cỏc dung dch: 1)dung dch th ng cha Zr, Ti ti u, 2) dung dch TiF62- 0,02M , 3)KCl 3% Trờn Hỡnh 3-3, quan sỏt s thay i th ngh OCP ca thộp cỏc mụi trng khỏc Trong dung dch cha ng thi Ti Zr s cho giỏ tr th in cc dng nht Ch cú TiF62- thỡ khụng th ci thin c OCP ca thộp Th in cc gim nhanh n giỏ tr n mũn ca thộp Trong KCl, in th ca thộp nhanh chúng dch chuyn v phớa õm in cc thộp khụng th c bo v dung dch KCl Khi nhỳng Fe vo dung dch ZrF62- hoc TiF62-, cỏc phn ng xy H2TiF6 + Fe + 2H2O = ZrO2 + Fe2+ + 4H+ + 6F- + H2 15 Footer Page 23 of 145 Header Page 24 of 145 H2ZrF6 + Fe + 2H2O = TiO2 + Fe2+ +4H+ + Fe2+ + 6F- + H2 ng thi, quỏ trỡnh thy phõn xy cng lm tng kh nng to mng trờn thộp c bit pH cao ZrF62- + OH- = ZrO2.2H2O + 6F- ZrO2 hoc/v TiO2 phỏt trin ti mt s v trớ tõm trờn mt Fe v phỏt trin thnh mng [18,19,20,23] Theo c ch ny, cú th xy s cnh tranh kt ta trờn in cc Fe S kt hp ca thnh phn TiF62- v ZrF62- cho c mng bin tớnh cú tớnh cht bo v tt hn mng cha Ti v Mo [24] 3.2 ng cong phõn cc ca mng bin tớnh Mu thộp c to mng bin tớnh dung dch ZrTi iu kin ti u nh trỡnh by phn trờn Mng th ng Cr (lm so sỏnh) cng c to trờn nn thộp bng cỏch nhỳng dung dch K2CrO4 0,1M thi gian phỳt ng cong Tafel thu c th hin trờn Hỡnh 3-4 1000 1000 100 100 10 Dòng điện (mA) Dòng điện (mA) 10 0.1 1 0.1 0.01 1E-3 1E-4 0.01 1E-5 -0.90 1E-3 -0.85 -0.80 -0.75 -0.70 -0.65 -0.60 -0.55 Thế điện cực (V/ Ag/AgCl) 1E-4 1E-5 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 Thế điện cực (V/ Ag/AgCl) Hỡnh 3-4 ng cong Tafel ca 1)thộp; 2)thộp c bin tớnh dung dch Zr Ti; 3) Thộp c bin tớnh CrO42- 0,1M Dung dch o KCl 3%, tc quột 10mV/s Cú th nhn thy, cú mng th ng, th n mũn khụng thay i nhiu, ch dch mt ớt v phớa dng Chng t mng bin tớnh ny (k c Cr) khụng th bo v, che chn cho nn Fe lõu di c Tuy nhiờn, dũng n mũn gim ỏng k Mng bin tớnh Cr (ng 3), cho giỏ tr n mũn nh nht Nn 16 Footer Page 24 of 145 -0.50 Header Page 25 of 145 thộp c bin tớnh bng ZrTi cng cho dũng n mũn gim ỏng k so vi ch nn thộp 3.3 Tớnh cht b mt ca lp ph (ti im ti u) 3.3.1 S to thnh lp bin tớnh Kt qu th hin trờn Hỡnh 3-5 Tổng trở / Ohm 10k 1k -80 2 -60 Roxide C -40 100 RE Coxide 10 100m 10 100 1k 10k Pha ( 100k -20 100k Tần số (Hz) Hỡnh 3-5 S thay i tớnh cht b mt ca in cc thộp trc(1) v sau (2) bin tớnh dung dch ZrTi Ph o dung dch H2SO4 10% Theo lý thuyt, cỏc s liu ca tng tr cú th biu din nh mt mch in tng ng Mch in cha cỏc thnh t th hin c giỏ tr ca tng tr Mch in c th hin nh trờn Hỡnh 3-6 in tr ca lp ngn cỏch ni song song vi t in l cú giỏ tr rt ln, c b qua Do vy tng tr xỏc nh ch yu l ca lp oxide: in tr Roxide v t in Coxide tn s cao, xỏc nh RE l in tr ca lp dung dch o Kt qu ph tng tr in húa trờn Hỡnh 3-5 cho thy tng tr, in dung ca mng ó cú thay i c trng tng tr th hin tớnh cht in ca vt liu Hỡnh 3-6 S mch in tng ng ca b mt thộp 17 Footer Page 25 of 145 Header Page 26 of 145 Roxide th hin xp, sớt cht ca lp oxide, Coxide c trng cho h s in mụi ca lp oxide Khi hỡnh thnh c lp bin tớnh trờn nn oxide ban u, in dung Coxide s thay i Bng cỏch nhỳng mu thộp vo dung dch ZrTi 1-2 phỳt, kt qu ph tng tr cú th quan sỏt c s thay i Coxide iu ny l cú c l lp bin tớnh ó c hỡnh thnh trờn nn thộp 3.3.2 Cu trỳc t vi Cu trỳc t vi v thnh phn nguyờn t trờn b mt mu c phõn tớch trờn mỏy SEM (Hỡnh 3-7) Trờn hỡnh a, vi mu thộp ban u, cú th nhỡn thy cỏc rónh sõu quỏ trỡnh ỏnh búng b mt a b Hỡnh 3-7 Cu trỳc t vi v thnh phn nguyờn t ca b mt Fe (a) trc v (b) sau bin tớnh dung dch cha Zr, Ti 18 Footer Page 26 of 145 Header Page 27 of 145 Cu trỳc mng bin tớnh cú cu trỳc khỏ c bit so vi ban u, cú th nhỡn thy nhiu cu trỳc ht nh trờn b mt, xự xỡ Cỏc vt rónh sõu ỏnh búng c hc mt hn Trong quỏ trỡnh to mng th ng pH=4, cỏc hp cht oxide ca Zr v Ti c hỡnh thnh Cú th to cỏc phc ca Ti, Zr, Fe v O Nh cu trỳc c bit ny ó ci thin kh nng chng n mũn ca mng Nhỡn vo kt qu EDX, ch cú th thy thnh phn Ti (khong 17% tớnh theo nguyờn t) Peak ca Zr khụng th hin Cú th cng ca cỏc peak Fe, Ti, S, K quỏ mnh nờn che khut, lng Zr cú th tham gia lp ph khỏ nh Phng phỏp EDX thc s khụng th cho kt qu chớnh xỏc vi hm lng Zr nh lp ph [18] C ch to mng th ng cú th trao i: nhỳng mu thộp dung dch cha ZrF62-; TiF62- cỏc phn ng ng thi hoc cnh tranh xy trờn mu thộp: Fe + H2ZrF6 + H2O = ZrO2 + 4H+ + 6F- + Fe2+ + H2 Fe + H2TiF6 + H2O = TiO2 + 4H+ + 6F- + Fe2+ + H2 Cú th cỏc anion b thy phõn: ZrF62- + OH- = ZrO2.2H2O + 6FTiF62- + OH- = TiO2.2H2O + 6F- Lp mng bin tớnh to trờn nn thộp ch yu l cỏc oxide ca Zr v Ti S cú mt ca Fe2+ lp bin tớnh cú th to nờn hp cht phc ZrxTiyFemOn õy l hp cht ó to nờn tớnh bo v cho lp bin tớnh [18,25,26] 3.4 Mng epoxy trờn nn thộp bin tớnh 3.4.1 Tng tr in húa Sau bin tớnh dung dch ZrTi, mu c sy khụ v ph mng epoxy bng phng phỏp ph quay (chiu dy khong 150-200 micromet) Kt qu th hin trờn Hỡnh 3-9, Hỡnh 3-10 Vi h ny, tớnh cht h c c trng bi mch in tng ng, th hin trờn Hỡnh 3-8 19 Footer Page 27 of 145 Header Page 28 of 145 Cepoxy Clp in tớch RE Repoxy Rth ng Hỡnh 3-8 S mch in tng ng ca h epoxy/thộp bin tớnh 1M C thu dong Rpolymer -80 100k 10k Cpolymer -40 phase () Tổng trở () -60 1k -20 100 10 100 1k 10k Tần số (Hz) Hỡnh 3-9 Ph tng tr in húa ca mng epoxy trờn nn thộp cha bin tớnh Ph thu c KCl 3% Thi gian ch o mu 60 phỳt Trờn Hỡnh 3-9, ph tng tr ca thộp mụi trng KCl c ghi li gi Theo thi gian, in tr mng epoxy gim dn, cú th quan sỏt vựng tn s 10-100Hz vựng tn s cao, thi gian ban u (khong 2-3 gi), mng khỏ bn, cú th ngn cn s xõm nhp ca mụi trng in dung mng gn nh n nh Theo thi gian, tng tr mng gim dn nhanh chúng Sau gi, ng cong tng tr nh ca mt nn kim loi Lỳc ny mng epoxy ó bo hũa mụi trng, dn in rt cao, tr ca mng gim nhanh chúng Ti b mt phõn chia pha, in dung C ca lp oxide gim nhanh chúng Bõy gi, vựng tn s cao, tng tr gn nh in tr ca dung dch Quan sỏt ng pha cú th thy s khỏc bit 20 Footer Page 28 of 145 Header Page 29 of 145 C thu dong R polymer -80 1M Cpolymer -40 10k phase () Tổng trở () -60 100k -20 1k 10 100 1k 10k Tần số (Hz) Hỡnh 3-10 Ph tng tr in húa ca mng epoxy trờn nn thộp ó c bin tớnh dung dch ZrTi Ph thu c KCl 3% Thi gian ch o mu 60 phỳt Trờn Hỡnh 3-10 l ph tng tr ca mng epoxy c ph trờn nn thộp ó c bin tớnh ZrTi Cỏc vựng c trng trờn gin Bode th hin khỏ rừ rng Trong sut thi gian o (8 gi), s n nh ca lp bin tớnh th hin qua s n nh ca in dung vựng ny vựng tn s cao, s thay i Cepoxy, s gim in tr mng vựng tn s 100Hz tt c l s xõm nhp ca mụi trng t bờn ngoi vo Tuy nhiờn, so vi mu khụng cú bin tớnh, in tr mng gim nhng khụng quỏ nhanh v trỡ mc in tr cao (khong 50 KOhm), iu ny chng t cú mt ca lp bin tớnh ó ci thin tớnh cht ca mng epoxy Lp bin tớnh ó ngn cn s thõm nhp ca mụi trng i qua lp tip xỳc epoxy/kim loi, khụng cho tip xỳc trc tip vi kim loi nn S cú mt ca lp bin tớnh ó hỡnh thnh lc Van der Waals, lc liờn kt H v ú lm tng bỏm dớnh ca lp ph hu c lờn nn kim loi [18,19,20] 3.4.2 ỏnh giỏ kh nng bo v ca mng Sau ph mng epoxy bng phng phỏp ph quay, mu c ngõm KCl 3% quan sỏt kh nng búc tỏch mng v s khuch tỏn ca mụi 21 Footer Page 29 of 145 Header Page 30 of 145 trng n mũn vo theo cỏc v trớ biờn Hỡnh nh thu c sau ngõm KCl 3% tun c th hin trờn Hỡnh 3-11 Hỡnh 3-11 Hỡnh nh b mt mu thộp c ph mng epoxy cú (a) v khụng cú (b) lp x lý bng bin tớnh dung dch ZrTi Cú th nhn thy mu a, vi s cú mt ca mng th ng, mng epoxy bỏm chc hn, ti biờn tip xỳc ớt b mụi trng KCl tn cụng Quan sỏt trờn b mt, khụng cú hoc rt ớt v trớ b mụi trng n mũn tn cụng trc tip, i xuyờn qua mng (trong mụi trng bóo hũa KCl) Cỏc vớ tr n mũn bờn di mng khụng quan sỏt thy c Vi hỡnh b, cỏc v trớ n mũn (mu vng) cú th thy c lan khp b mt mu õy l cỏc sn phm n mũn Mu ca mng epoxy ó bt u bin i mu Cng cú th quan sỏt vi trũ ca lp bin tớnh bo v mng mng epoxy mu c ngõm trc tip vo KCl 3% 5h Hỡnh nh cỏc mu th hin trờn Hỡnh 3-12 22 Footer Page 30 of 145 Header Page 31 of 145 a b c Hỡnh 3-12 Hỡnh nh phỏ hy mng epoxy trờn nn thộp a)nn thộp c th ng dung dch Cr, b)nn thộp th ng dung dch ZrTi, c) thộp nn khụng cú lp bin tớnh Thi gian ngõm mu gi KT LUN ti ó trung gii quyt c cỏc sau: - ó tỡm c ch to lp mng bin tớnh trờn nn thộp thng bng cỏch n gin, d thc hin nhỳng mu thộp vo dung dch bin tớnh t 1-2 phỳt Dung dch gm 0,01 M TiF62-, 0,02M ZrF62-; pH dung dch bng 4; - Bng phộp o in húa (ng cong phõn cc, ng Tafel) cho thy mng th ng ó cú hiu qu vic nõng cao chng n mũn cho mng hu 23 Footer Page 31 of 145 Header Page 32 of 145 c epoxy th hin qua: gim dũng n mũn, chuyn th in cc v phớa dng hn - ó c trng c tớnh cht ca lp bin tớnh: dựng kt qu ca ph tng tr in húa th hin ó hỡnh thnh lp bin tớnh qua s thay i in dung ca lp b mt Cỏc nh chp SEM cho thy cu trỳc khỏ c bit ca lp bin tớnh, phõn tớch nguyờn t EDX khụng th hin c s cú mt ca Zr Cú th hm lng Zr thp, cỏc pớc khỏc mnh hn ó che chn khụng th hin rừ - S cú mt ca lp bin tớnh ó tng bỏm dớnh qua kt qu ngõm mu cú ph epoxy KCl Epoxy ph trờn nn kim loi cú bin tớnh cú th c ci thin Ph tng tr cng cho kt qu phự hp vi kt qu ngõm mng TI LIU THAM KHO [1] Trnh Xuõn Sộn, n mũn v Bo v kim loi, NXB i hc Quc gia H Ni, 2006 [2] Vale rie Sauvant-Moynot, Serge Gonzalez, Jean Kittel, Self-healing coatings: An alternative route for anticorrosion protection, Progress in Organic Coatings 63 (2008) 307 315 [3] Ahmad Ghasemi-Kahrizsangi, Homeira Shariatpanahi, Jaber Neshati,Esmaeil Akbarinezhad, Corrosion behavior of modified nano carbon black/epoxy coatingin accelerated conditions, Applied Surface Science 331 (2015) 115126 [4] SungMo Park, MinYoung Shon, Effects of multi-walled carbon nano tubes on corrosion protection of zinc rich epoxy resin coating, Journal of Industrial and Engineering Chemistry 21 (2015) 12581264 [5] Sironmani Palraj, 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corrosion resisitance of organic coating with conversion layer containing Ti, Mo, Tp chi KH v CN, Vin Hn lõm Khoa hc v Cụng ngh Vit Nam, Tp 53-S 4A, 80-86, 2015 (2nd International Workshop on Corrosion and Protection of Materials 26-29 October 2015, Ha Noi, Viet Nam) 25 Footer Page 33 of 145 Header Page 34 of 145 [25] O Lunder, C Simensen, Y Yu, and K Nisancioglu, Formation and characterisation of Ti Zr based conversion layers on AA6060 aluminium, Surf Coatings Technol., vol 184, pp 278290, 2004 [26] S Adhikari, K A Unocic, Y Zhai, G S Frankel, J Zimmerman, and W Fristad, Hexafluorozirconic acid based surface pretreatments : Characterization and performance assessment, Electrochim Acta, vol 56, no 4, pp 19121924, 2011 26 Footer Page 34 of 145 ... conversion solution containing Zr, Ti - Characterisation of material with SEM, EIS, EDX and Open Circuit Potential; - Ti, Zr of conversion layer can improve the corrosion protection of organic coating... the corrosion protection of organic coating Creativeness and innovativeness - Forming of conversion layer with Ti, Zr chemically - Enhancing the protection ability of epoxy coating Research results... Duong Thi Hong Phan Implementing institution: The University of Danang Duration: From Sep 2015 to Sep 2016 Objectives - Fabrication of conversion layer consisted of Ti, Zr chemically - Conversion