DANH GIA TAC DONG CUA M 6 I T R U C I N G N U 6 C B I £ N D ^ N KIM LOAI VA MANG SON
Ddo Trpng Hien, Vo Di, Nguyin HUu TU
TOM TAT
Nhiiu loai thilt bj thudng dupe dung trong cdng tac nghidn cflu biln. Tuy nhidn trong dilu kidn nudc biln cung vdi khi hdu nhidt ddi Viet nam, cac phdn kim loai va ldp son bao vd ludn bi an mdn va pha buy. Bai bao trinh bay dilu kidn an mdn va pha buy tu nhidn. Dua trdn co sd cd dupe chflng ta phai dl xud't cac giai phap huu hidu nham ban che su thidt hai nay.
I. M 6 D A U
Trong thdi gian vai nam vfla qua, Phan vidn Hai duong hpc Ha ndi da dupe ddu tu chiiu sdu nhdm ndng cao nang luc khao sat nghidn cflu bien. Mdt loat cac may do, may phan tich mdi va hidn dai dupe trang bi cho cac phdng nghidn cuu.Tfl 1993 dd'n nay, nhiiu chuyd'n khao sat bien da dupe tid'n hanh, Phan vidn da thu dupe mdt lupng ldn cac so dja chat, dja vat ly va khi tupng hai duong phuc vu cho cac dl tai, dl an nghidn cflu khoa hpc. Song kem theo dd mdt sd cac thid't bj cung bj hu hdng, mdt phdn do bi tidu hao trong qua trinh sfl dung, cdn mdt phdn dang kl la bj pha buy bdi mdi trudng bien.
Dl tha'y rd cac tac ddng efla mdi trudng nudc biln de'n su pha buy cac thid't bi nghidn cflu khoa hpc nhu thi nao, vdn de nay se dupe dl cap mdt phdn trong bai bdo cua cac tac gia.
2. MOT SO DAC DIEM AN MON KIM LOAI CUA MOI T R U 6 N G NUdC BIEN 6 VIET NAM
Mdt trong nhflng dac tinh co ban efla mdi trudng nudc biln la an mdn kim loai va pha buy mang son, gay ra su pha buy cac thid't bj, may mde chl tao tfl kim loai. Mdi trudng biln cd boat tinh an mdn va pha buy rdt cao dd'i vdi cac vdt lieu nhu thlp, hpp kim, son, betdng v..v...Mpt tdp hpp da dang cac hinh thai khi hdu nhiet ddi gid mfla khac nhau vl nhiiu mat trdn lanh thd Viet Nam lai cang tao dilu kidn thudn lpi cho qua trinh an mdn va pha huy nay[l].
Su an mdn kim loai do nud biln cd the xay ra vung trong mun bien, vung triiu, vflng tl nudc, vung khi quyen trdn vflng tl nudc, vung nudc bien ndng gdn bd, vflng nudc sdu thim luc dja, vflng dai duong sdu [2]. Trong bai bao nay chi dl cap tdi vdn de anh hudng cua mdi trudng nudc biln tdi qua trinh an mdn va pha buy vat lidu kim loai, ma dupe xem la nguydn nhan chinh gay ra su pha hdng cac thid't bi nghidn cflu hai duong.
De tha'y dupe tdc dp an mdn kim loai trong vung nudc bien Viet Nam mdt sd mdu kim loai dupe chpn de thfl nghidm la thlp cac bon (chid'm khoang 66%), ddng (chid'm khoang 3%) va cac hpp kim nhdm. Cdc hpp kim ddng va nhdmdupc sfl dung nhiiu trong mdi trudng biln vi nd cd tinh bin cao trong mdi tudng nay[3,4].
An mdn biln la mdt qua trinh didn hod vdi chd't khfl phdn cue la d xy cd thi bilu didn bdng mdt so dd don gian:
- Qud trinh a-ndt:
ne -^ [ne Me"1 ''H^0 ->Me"^+mH,0 -Qud trinh ca-tdt
O2 + 4e + 2H2O -> 40H
Qua trinh catdt cdn tdn tai cbdt khfl cue hydro:
H ^ - i - e - ^ H - ^ H + H - ^ H ^ .
Tuy nhidn trong nudc biln 0 Nha trang va Quang ninh, vdi dp pH « 7.84 -^ 8.3, do dd qua trinh khfl phan cue hydro trong nudc biln vdi cac vat lieu CT3, nhdm, ddng khdng dang kl va cd thi bd qua. Su an mdn cac kim loai va hpp kim trong nudc biln tuan theo nhutig quy luat dudi day [51.
Quy lugt 1
Td'c dp an mdn thlp CT3 d vflng te nudc ldn hon rdt nhiiu so vdi td'c dp an mdn cua CT3 trong nudc biln. 6 chu ky 6 thdng, 9 thang va 12 thang thfl nghidm, td'c dp an mdn cua CT3 d dd cao 0,8m so vdi mat nudc biln, ldn gap 4-6 ldn so vdi td'c dp an mdn ciia CT3 d dp sau 1,2m trong nudc biln.
Td'c dp an mdn cua CT3 d dd cao 1,2m va 2m each mat nudc biln va d mdm nudc biln diu nhd td'c dd an mdn cua nd d 0,8m. Vay d dp cao each mat nudc biln 0,8m chung ta cd mdt dinh vl td'c dd an mdn ( xem bang 1).
Bdng I: Quy ludt dn mdn thip GT3 theo vi tri thd nghiem
Vj tri thfl nghidm (m)
2,0 1,2 0,8 0 -1,2
Td'c dp an mdn (mm/nam) 1thang
0,31 0,83 1,62
0,7
3 thang 0,28 0,55 1,05 0,65 0,56
6 thdng 0,15 0,45 1,16 0,33 0,23
9 thang 0,41 0,44 0,77 0,21
1 nam 0,54 0,31 0,65 0,25 0,16 Su thay ddi td'c dp an mdn kim loai theo dd cao so vdi mat nudc biln dupe md ta bdi dd thj dudi day:
2 -
E I
.<«•
fi1,2-
tDX) . f i
i ^.0,8-
s e
> s
0
1 -1,2-
—.j
•j/ 1 thang
\/ \ . 6 than!!
K \
; \ \ .. .. 12 thang
» 1 *
l//
• / i A 1 1
1 Tdc do an mon / (mm/nam)
•
•
Vflng te sdng nam trong dai dp cao 04-2,4m trdn mflc nudc bien trung binh, khi dd td'c dp an mdn efla thlp cacbon dat cue dai d khoang dd cao 0,6m-^l,2m, tuy thudc vao tiitng vflng biln [6].
Cl tram Nha Trang, cac thfl nghidm dupe thuc hidn trdn phao, ndn thay ddi triiu khdng anh hudng dd'n vi tri dp cao cua mdu phoi so vdi mat nudc bien.
Khi quan sat cac cot cdng trinh biln, mdt sd tac gia da nhdn thd'y rang, td'c dd an mdn cac cdt phu thudc vao dd cao each mat nudc bien. Tai dd cao 0,8m td'c dd an mdn cua thlp ldn gdp 5 ldn td'c dd an mdn cua thlp d gdn mat nudc bien [7].
Farkhdov (OapxflOB) cho rdng d vflng cd dp cao 0,5m dd'n 1,5m va dd'n 3,0m trdn mflc nudc bien, thlp cd td'c dp an mdn rdt ldn khoang 0,8mm/nam. Ddy la vung an mdn nguy hiem nhd't, cdn phai cd mdt phuong phap bao vd chdng an mdn thich hpp [8]. Tdc dd an mdn ldn d dp cao nay rd't cao do cac nguydn nhdn chinh sau ddy:
Do su tich tu mdt lupng mudi rd't ldn trdn bl mat cua thlp va tdn so cao cua su thay ddi khd-udt.
Do qua trinh khfl phdn cue catdt cua dxy khdng khi, cdng vdi su khfl phdn cue catdt do ldp gi theo phan utig: Fe203 + 2e ^ 2FeO + 20H".
Trong dilu kidn an mdn dudi mang dm mdng, su tang nhidt dp khdng khi cung nhu tang cudng dp bfle xa mat trdi lam tang cudng qua trinh phan utig khi tdn tai qua trinh khfl phan cue la dxyt sat 3 (Fe203). Mua lam anh hudng dd'n qua trinh lam trdi ldp gi bl mat va cd thi lam tang td'c dp phan flng...
Quy luat 2.
Td'c dd an mdn cac kim loai d vflng trdn mat nudc biln va trong nudc biln diu giam theo thdi gian. Tuy nhidn trong vflng biln Nha Trang, td'c dp an mdn d dp cao 2,0m trdn mat nudc biln thay ddi chua theo quy luat nay va cdn cd chieu hudng tang. CJ dd cao 0,8m trdn mat nudc biln td'c dp an mdn CT3 sau 1 nam thfl nghidm giam 2,5 ldn so vdi td'c dp an mdn cua nd sau mdt thang thfl nghidm.
Td'c dp an mdn CT3 trong nudc biln sau mdt nam thfl nghidm giam 4,5 ldn so vdi td'c dp an mdn cua nd sau mdt thdng thfl nghidm.
Td'c dp an mdn Cu sau 12 thang thfl nghidm trong nudc biln giam 3,3 ldn so vdi 3 thang thfl nghidm...
Td't ca nhflng nhan xit trdn dupe chi ra d bang 2.
Bang 2
Tram Nha trang Quang
ninh
Kim loai, Hpp kim CT3 Cu CT3
Cu
Tdc dp an mdn (mm/nam) 1thang
0,7 0,241 0,065
3 thang 0,56
0,1 0,182 0,033
6 thang 0,23 0,05 0,171 0,019
9 thang 0,21 0,034 0,149 0,018
1 nam 0,16 0,03 0,136 0,017 6 trong nudc biln Quang Ninh, td'c dp an mdn thlp CT3 d trong nudc biln sau mdt nam thfl nghidm giam khoang 2 ldn so vdi mdt thang thfl nghidm va efla Cu giam 3,2 ldn. Nguydn nhdn cua su giam td'c dd an mdn theo thdi gian la:
- O vung an mdn trdn vung nudc biln, ldp san pham an mdn trdn bl mat kim loai kim ham qua trinh khud'ch tan d xy tfl khdng khi vao bl mat kim loai [8].
- Dd'i vdi kim loai d vflng trong nudc biln su giam td'c dd an mdn kim loai cd thi do 2 nguydn nhan: ldp san phdm an mdn trdn bl mat kim ham qua trinh khud'ch tran d xy tfl nudc biln vao bl mat kim loai va ldp sinh vat bam ban ddy dac, ldp np chdng ldp kia cung kim ham qua trinh khud'ch tan d xy tfl nudc biln vao bl mat kim loai. Tuy nhidn chi cd loai sinh vat bam bdn mdi cd kha nang nay [9,10], cdn ldp sinh vat bam bdn la thuc vat thi tang td'c dd an mdn do trong qua trinh sinh trudng, quang hpp tao ra cho mdi trudng xung quanh (trdn bl mat kim loai) mdt lupng ldn d xy [10,11]. d vjnh Nha trang, sinh vat bam b^n chfl yd'u la ddng vat (ballanus, ostrea cuculata boin, sipon...) ndn tdc dd an mdn cac vat lieu giam manh theo thdi gian thfl nghidm.
Ddi vdi ddng (Cu), sau 9 thang thfl nghidm trong nudc biln xua't hidn nhiiu sinh vat bam ban mac du idn ddng la ddc to dd'i vdi sinh vat bam ban. Ly do co ban la td'c dd an mdn ddng giam theo thdi gian, do ldp san phdm an mdn tao ra trdn bl mat lam giam td'c dp an mdn: 3 thang ddu td'c dd an mdn 0,102 g/m^h. Td'c dd nay ldn, tflc la idn ddng tao ra tren bl mat nhiiu cd thi gdy ddc cho sinh vdt bam. Sau 9 thang thfl nghidm, td'c dp dn mdn cua ddng 0,034g/m^h, lupng idn ddng khdng dfl ldn de gay dpc cho sinh vat bam bdn. Dilu nhan xet nay phfl hpp vdi cac kit qua nghien cuu trong de tai 48D-01-02.
Td'c dp an mdn ddng ldn hon 0,05g/m^h, khi khdng cd sinh vat bam b^n trdn bl mat ddng, nd'u td'c dp boa tan ddng nhd hon 0,05 g/m^h, cd sinh vat bam ban tren bl mat ddng.
Tdng hpp vl td'c dp an mdn cua thlp ddng tau CT3 trong nudc biln ndng ven bd Viet Nam sau 1 nam thfl nghidm: 0,132 mm/nam [13], 0,146mm/nam [12], 0,136mm/nam (kd't qua cac nghidn cflu d Quang Ninh ndm 1998), 0,16mm/nam (kd't qua cdc nghidn cflu d Nha Trang nam 1998).
Td'c dp an mdn thlp cac bon sau 1 nam thfl nghidm trong nudc bien vflng Caribd va Panama (vflng nhidt ddi) la 0,135mm/nam [14]. Nhu vdy td'c dp dn mdn d ven biln Viet nam dao dpng khoang 0,13 ^ 0,16mm/nam; trung binh la 0,145mm/nam. Cac thfl nghidm qua nhiiu ndm cho thd'y, td'c dp an mdn CT3 trong nudc biln Viet Nam it thay ddi va cd thi Idy gia trj trung binh la 0,145mm/nam. Gia trj nay xa'p xi vdi td'c dp an mdn thlp cdc bon d cac vung biln nhidt ddi khac trdn the' gidi.
Quy luat 3.
Quy ludt phat triin sinh vat bam ban (trdn vat lieu) d vjnh Nha Trang. Sinh vat bam ban trong nudc bao gdm sinh vat co ldn (macroorganism) va vi sinh vat (microorganism). Hidn nay ngudi ta da tim thdy khoang 2000 loai (ca ddng vdt va thuc vat) dudi phdn day cua tau bien [15]. Chflng la mdi nguy hai cho tau biln va cac cdng trinh biln:
Dd'i vdi tau biln, sinh vat bam phat trien phia dudi nudc cua vd tau, tang trpng tai, giam td'c dp, tidu hao nhiiu nhidn lieu.
Lam tdc dudng dng ddn nudc.
Pha buy mang son tau bien, cac cdng trinh biln
Gdy an mdn dilm (local corrosion), dac bidt la an mdn Id (pitting corrosion) [16].
Cho dd'n nay da cd nhiiu cdng bd vl sinh vat bam bdn va tac hai cua chung dd'i vdi kinh t l va ky thuat.
Trong vung vjnh Nha Trang sinh vat bam b^n phong phu va phat trien nhanh trdn cac mdu thfl nghidm. Lupng sinh vat bam sau 12 thang ngam mdu thfl nghidm la 6676 g/m^ trdn CT3; 9817g/m^ trdn ddng; 6318 gim' trdn nhdm (sau 6 thang) va 10916g/m^
trdn thlp khdng gi (sau 1 nam ngam mdu).
Nguydn nhan su phat trien rdt manh cua cac sinh vat bam ban d vjnh Nha trang la do cac chdt dinh dudng tfl 2 con sdng ldn (sdng Cai va sdng Con) dd ra vjnh, ddc bidt la vao mua mua. Cdc chd't dinh dudng cd vai trd phat trien sinh vat bam b^n la nitrat(N03), nitrit(N02), phosphat(P04) va cac chd't huu co tfl nudc thai sinh boat va cdng nghidp.
^ Sinh vat bam bdn d vinh Nha Trang phdt tri'ln qua 2 giai doan. Giai doan ddu (khoang 3 thang ngdm mdu thfl nghidm), trdn mdu xuat hidn mang nhdy gdm cac diatoms, rong dang spi, ddng vat nguydn sinh va cac vi khudn.
Giai doan 2: sau 3 thang ngam mSu trd di, khi dd xudt hidn cac sinh vat ldn, bao phu toan bd bl mat mdu, bam rdt chdc. Co chl cua su bam dupe Ragg [15] giai thich mang nhdy d giai doan ddu la nin cho cac du trflng ballanus va bao tfl hinh qua Id cua rong bam vao, phdt triin rd't nhanh qua nhiiu giai doan phfle tap. Trong qua trinh phat triin chflng tid't ra chat keo bam rdt chdc. Nd'u son td't, chdt ddc td cua son dfl dl lam ddng tu keo hoac nhidm ddc co thi sinh vdt bam, cd thi lam chd't cdc sinh vat nay.
San phdm an mdn dudi ldp sinh vat bam cd mau den cua sulfua sdt II (FeS).
Nguydn nhdn tao ra FeS do^ su khfl cue efla loai vi khudn khfl sulphat (desulfovibro desulforican), la loai vi khuan yd'm khi (anaerobic bacteria). Qua trinh nay xay ra theo CO che nhu sau :
4Fe -> 4Fe'^-8e- : Phan flng a-ndt
8H2O -^ 8H^ + S0H- : Phan flng phan ly cua nudc 8H^ +8e- -^ 8H : Phan flng ca-tdt
SO/- + 8H ^'^^^^-^'^ ) S'-+ 4SO2 : Phan cue ca-tdt do vi khuan Fe^^ + S^" ^ FeS : San phdm an mdn
3Fe'^+60H. -^ 3 Fe(OH> '2
Phan Aug tdng cdng :
4 Fe'^ + SO4'- -^ 3Fe(OH)2 + FeS + 20H-
San phdm an mdn trong trudng hpp nay la bydroxyt sat hai (Fe(0H)2) va sulfua sdt hai(FeS) vdi ty Id 3/1, va vi vay chflng cd mau den.
Cac thid't bj nghidn cflu hai duong cua chung ta khi boat ddng trdn biln se chju anh hudng cua ca ba quy ludt trdn, ddn tdi cac su cd hdng hdc. Qua trinh an mdn va pha buy ldp bao vd ( vd may) efla thid't bj. Khi ldp bao vd khdng cdn an toan thi cdc phdn bdn trong, tflc la cac khdi kit cdu cua may bj pha hdng,thid't bj se ngihig hoat ddng.
KfeT L U A N
Cdng tdc khao sat nghidn cflu biln ludn phai sfl dung cdc thid't bi. Tuy nhidn, su an mdn va phd buy cdc thid't bj dd trong mdi trudng nudc biln cflng vdi dilu kidn khi hdu nhidt ddi ndng dm cua Viet Nam la hidn tupng cdn dupe quan tdm va cdn cd bidn phap tich cue dl ban chl dd'n mflc thd'p nhd't hidn tupng bd't lpi nay. Trong qua trinh sfl dung cdc thid't bj hai duong, phai tudn thu mpi chl dp nghidm ngat bao quan, bao dudng thid't bj nghidn cflu biln, cd nhu vay tudi thp cua cac thid't bi hai duong mdi dupe duy tri.
TAI LifiU THAM KHAO
1. Pham Ngpc Toan, Phan Tat Ddc. 1993. "Khi hau Viet Nam" Nha xuat ban Khoa hpc Ky thuat, trang 3-9.
2. M. Schumacher. 1979. "Seawater Corrosion Handbook" Noyes Data Corporation Park Ridge, New Jersey U.S.A. 1979, p.8
3. B.C. CMHJIBCKIIM, B. BaiibKOB, P.M. ByflOB , 1979 Kopposun v\
Sau^MTa ArnoMMHeBbix CnnoB. Msfl. "MeTajinyprun" MocKsa, c i p 184
4. E.M. SuMHeBa, JI. I/I. LiJM6anoB , 1963. MopcKan Koppoanfl MeflHbix CnnanoB. l/l3fl. "CyflnpoMriia" JleHUHrpafl 1963.
5. " Bao cao dl tai nghidn cuu cdp Nha nudc giai doan 1996 - 1998" Trung tam Khoa hoc tu nhidn va Cdng nghd Qud'c gia - Vidn Vat lidu
6. X.zhu, G. Huang and C.Liang 1996. Proceedings of 13"" Intemational Crrosion Congress. November 25"" 29*, 1996. Melbourne Australia, p. 389
7 U.K. Boropafl, E.B. HcKpa, B.A. KnuMOBa, K).Jl.Ky36MMH,1973.
KopposMfl M SamMTa MopcKnx CyflOB. Hsfl. "CyflocTpoeHi/ie" JleHUHrpafl 1973, CTp. 31
8. A. A. OapxaflOB , 1982. KaroflHan Saii^nTa or Koppoann CrajibHbix Coopy>KeHMti B MocKOM Bofle. M3fl. TocTonrex" MocKsa 1982, CTp. 24.
9. M. fl. ToMai^OB , 1965. Tepnoa Samma v\ Koppoann MeranoB. H3A.
A. H. CCOP MocKBa 1965 , c i p . 405
10. M. B. YnaHOBCKUM, JI. A. Po3e6epr , 1983. MMKpo6MOMecKan Koppo3Mfl MerajiOB B MopcKOM Bofle. M3fl. "HayKa", 1983, crp. 100
ll.C.R.Das. K . G . Mushra.Biologically Induced Corrosion. Proceedings of Intemational Conference on Biologically Induced Corrosion. June, 10-12-1985, f .114.
12. Tdng kd't dl tai Nha nudc 48 D. 01.02-1990. (Chuong trmh nhidt ddi 1985- 1990).
13.Tdng kit de tai Nha nudc 48 D. 01.02-1990. (Chuong trmh nhidt ddi 1980- 1985)
14. C.R. Southell, J.D. Bultman. Corrosion of Metals in Tropical Environments.
Final Report of 16 years exposures. Material Performance, July 1976, p. 15
15.J1.51. nonnnoB 1969. Hosbie ncnbijaHUM B MopcKOM BOfle B eCTeCTBGHMblX ycnoBMflx.
16. M. A Shide, Li Xan Tao, Huang Xin Ming 1995. Proceeding of The 19'" Asian - Pacific Control Conference , Taiwan, November, 5 - 10 , 1995 , P. 441
SUMMARY
Evaluation of sea water environment's impacts on metal and paint pellicle By Dao Trong Hien, Vo De, Nguyen Huu Tu
Equipments are often used in marinal survey. However, it is necessary to concern the corrosion and destruction of metal and paint pellicle under sea water together with
tropical weathet in Vietnam. This article will present the nature of corrosion and destruction process. On the basis of the study, we can have positive solution to restrict this disadvantage.
Ngudi sfla bai: TS Nguydn Van Luong Phan vidn Hai duong hpc tai Ha Ndi