Anh hu'O'ng chu ky am va do pH cua moi tru'O'ng dat den kha nang an mon cua thep
Influence of pH and moisture content of soil enviroment on corrosion rate of steel
Ngay nhan bai; 16/12/2014 Ngay sij^ bai: 20/01/2015 Ngay chap nhan dang: 27/02/2015
Le Anh Tuan, Phan Dure Hung
T C M
TAT:
Cac tinh phia Nam cua Viet Nam co khi hau va nhiet dg thay doi hen tuc trong nam, gay i n h hifcing den do am va do pH cua m6i tnl6ng dat. Svf thay doi nay lam anh hudng den dg ben ciia vat li^u thep lam viec dat nen. Thvfc nghiem nghien ciJu anh hticing cua moi triicing dat tai Vung Tau, Long An va Can Tho den qua trinh an mon cua thep bang each thay d6i dg am va do pH ciia moi trt(6ng, Danh gia sU an mon cua thep bdi sU thay doi chu ky kho am va pH ciia dat. Ket qua thUc nghidm cho thiy t6c d6 an mon vat li^u thep trong ba m6i tru6ng dit khde nhau ciing khac nhau tuy co cung dp am va do pH. T6c d6
in m6n th^p trong m6i trddng dit cijng phu thuOc nhi^u vio dg am va dp pH. Toe do anm6n cao vdi dat Vung Tau vdi 40% am, vdi dat can Thd v i Long An la 90%. Khi nong d g p H ciia ca 3 loai dat d 6 , 8 10 va 12 thi toe dg an mdn dgt 0,1 - 0,2 mm/nam. Khi mdi trildng p H thay doi theo chu ky tiT 6 den 12 thi toe dg an mon trong dat Viing Tau dgt 0,56 mm/nam. Vdi mdi tnidng dat Long an va Can Thd thi toe do an mon la 0,1 mm/nam,
Tii khoa: dat, dg am, dg pH, ehu kf khd am, toe dg an mdn.ABSTRACT
The changes of climate and temperature in the southern provinces of Vietnam throughout the year influence the moisture and pH of the soil. These changes affect durability of steel materials embeded in soil. Experiments are executed to study the affect of soils obtained in Vung Tau, Long An and Can Tho to the corrosion of steel by various humidity and pH of soil. The corrosion of steel materials is evaluated by changing the moisture cycle and pH of soils. The experimental results showed the corrosion rates of steel materials are difFerent in three soil environments having the same moisture and pH. The corrosion rate of steel in soil environment depends on the moisture and pH. Hence, the corrosion rates are highest on 40% and 90% for Vung Tau soil and Long An, Can Tho soil, respectively During pH value at 6, 8, 10 and 12, the results shows the values are 0.1-0.2 mm/year in various environment soils. Moreover, in pH cycling investigation, the corrosion rates are about 0.56 mm/year and 0.1 mm/year in Vung Tau and Long An, Can Tho soil, respectively
Keywords: soil, moisture, pH, wet-dry cycling, corrdsidn rate.
TS. L6 Anh Tuan
Khoa Ky thuit Xay Difng, Dai hgc Bach Khda Tp.HCM Email: latuan@ hcmut.edu.vn Mobile: 0937464284
TS. Phan Dufc HungKhoa Xay DUng va Cd hgc iing dung, Dai hgc Sii pham Ky thuat Tp.HCM, Viet Nam.
Email: [email protected] DT: 0916548639
I.GlOlTHlEU
An mon kim loai la sir ph^ iiOy vat lieu kim loai khi CO sU tifcJng tac hoa hgc hoac vat ly giu'a chung vdi moi trUdng an mdn. Qu^ trinh an mon kim loai dien ra trong rat nhieu moi trudng, trong do co moi trifdng dat. Hien nay, ng^nhxSy dung sCrdung rat nhieu cac cau kien thep dat trong dat nhi/ coc ong th^p, coc van thep, he th6ng ong dSn nUde Vi viy vin 3i an mon thep trong m6i trudng dSt r^t ding quan tam.
Nghien cu'u cua phdng Bcio ve Kim loai ciia Vien Kythuat nhiet ddi, Vien Khoa hoc va Cdng nghe Viet Nam da tien hanh thd nghiem danh gia qua trinh an mdn thep trong mdi tru'dng dat Wet Nam tit nam 1997. Nhdm nghien cdu Nguyen Van Chien, Le Van Cudng, Li Ddc B3o [2] da thd nghiem vdi mau thep cacbon thap trong mdi trudng dat vung ngSp man va doi ndi tai Ha Long, QuSng Ninh. Nhdm nghien cdu da ket lu^n rSng, qua trinh hn mdn thep trong moi tru'dng dat la qua trinh hap phu hoi nudc trong dat len be mat kim loai den gia tn tdi han nao dd. Ho da ket hop cac thdng sd dien trd suat va do am bing phuong ph^p do phan cue dien hda de xac dmh cic giai doan, qud trinh an mdn.Trong nghidn cdu tren, ngoSi cic nhan to nhu do Im, dien trd suit inh hUdng den qua trinh an mdn thep, cdn cd nhilu nhan td khac tac ddng, Mdc do thep bi an mdn trong mdi trudng dit cdn phu thudc vao tinh chat cCia dat, nhiet dd, vi sinh vat, do thdng khi cCia dat.
TSc gia R, Winston Revie vh Herbert H. Uhlig [3] lam thi nghiem hn mdn th4p vdi nhilu loai dat nhu dit dim tay, dat set, dat set lin sdi san.
Ket qui cho thay ring mdc do an mdn thep trong mdi trUdng dat phu thudc vio loai dat, thanh phin hda, thanh phan khodng v i ddday cda Idp dat thi nghiem nhu tren Hinh 1.
IWdt sd nghien cifu khac cho thiy ring dien trd suat dnh hudng rat nhieu d^n qui trinh an mdn cda thep trong dit, gia tri dien trd suit nay phu thudc vao thanh phan cua tdng loai
991
Hinh 1. Qui trinti an mon cita tliep tnjng dat [i]
I 007 j i 006 roos •
| 0 0 3
^ 002 1 0 01
0 L - .
g .U.,A
1 DLoiiBL 1 1 1
I L
VOng TAu Long An cAn TTKT D|adltni Hinti 2. Tfic dg an mon d moi tnfimg dai khac nliau, d6
t °'
— 008 c 006 u 004 O I Q
BLoaiA i
°""'° t
u^ m K
D 4 l i n | % ) Hinh 4. Toe doan mon va do am dat Long An
1
£ 02
S
• •L08IA H DLonU
S 01 1 005
0
k JlJ
. oieP
1 » " '
1 012 5 01 ^ c ooe - S 006002 -1 cL
e.L B U
aiA ^ ^ ^
^'^ B 1^
Dt I m |K)
ih 3, Toe d$ an mdn va do am dat Vung Tau
B i n g l . T h i n h p h i n c o l y c i j a d i t
Dttirni'A)
Hlnh S Toe do an mon va 36 am dat Can Tha
Tinh chat Od am t u nhien, W Dung trpng Udt, g . Dung trong khd, gu H^ SO rdng, eo Gidi han d4o,LL Gidi han chSy, Pi Chl sd d t e . IL
D o n v i
%
g / c m ' g / c m '
%
% %
Long An 36,3 1.87 1,37 1,07 51,7 28,3 13,4
Can Tho 45,1 1,74 1,20 1,29 47,6 25,2 22,4
VungTSu 24,9 1,94 1,56 0,73 38,6 22,1 16,5
dat, Thanh phan dat va dd am khi dd se in^
hudng d^n d o pH cua d i t v i ciJng i n h hudnj khdng nhd d^n qua trinh hn m d n . Vdi mfii t r u d n g dat cd d o a m cang ldn, t h i mdc d$ in m d n t h e p cang cao, khdi luang th4p bi an m6n cang nhieu. Khi xet den khS nang gay an m6n, dp am t r o n g d i t cd Snh h u ^ g nhifiu nhat so vdi yeu t d khac, tang d o am cua d i t se tang tin)jl<
xam thuc cua nd. An mdn se x i y ra it trong mS
t r u d n g khd rao. [4-7] • Nghien cdu ciia tac g i i Osaki dUa ra y f i u ^
quan trpng anh hudng din mdc dp an m6n 1^
dd pH Vdi d o pH cang nhd (pH < 4) thi t f l c a H . an mdn cang tang, dieu nay diing khdng ctil ddi vdi mdi t r u d n g d i t , mh cdn phiJ hop vdi thi nghiem trong mdi trUdng [8,9]. ' "mm
Nghien cdu nay thUc nghiSm x^c djnii t S T "
d d an m d n cua vat l i f u thep trang mdi tn dat tai Vung Tau, Long An v i C i n Tho. B i n h tdc d o an m d n cda vat lieu t h ^ p trong distil d o am, d o p H xac d m h va thay d6i theo chu 2. NGUYEN V A T L I | U V A PHI/ONG PHAP,' NGHIDM
2 , ; Nguyen vdt liiu
2.inhep m Vat lieu thep diJng cho nghien cdu cdthSii^
phan hda chda 0.08% C, 0.02% Si, 0.32% M F |
0.03% P, 0.03% S ^ 2.1.2 Vdt lieu ddt
Bit dugc lay tai 3 khu vi/c Vung TSu, Long An va Can Tho cd thanh p h i n co ly trinh bJy trong Bang 1.
2.2 Phuang phdp tgo mau vd thinghiem D p a m cua dat dUOC x^c dinh theo ASTM D2216. D p pH cua dat xac dmh theo ASTM 4972-95a. Tdc d p an m d n cua thep trong moi trudng t h i nghiem dUOc xac dmh theo tieu chuan ASTM G 3 1 - 7 2 .
Thi nghiem an m d n cCia thdp duoc thifc hien bang 2 n h d m . Nhdm A la nhCing mau thip duoc dat tiep xuc ci 2 mat trong mdi tri dat Nhdm B la nhdng mSu thep cd 1 m ^ t t j xiic vdi mdi t r u d n g dat v i 1 m | t tiip xO'c moi trudng khdng khi, Mdi trUdng d i t cd dO thuc nghiem la 20,40 va 90%, Chu kj khd' duoc thuc hien b i n g cdch cho d i t dat d d l l bao hda rdi say kho den khdi luong khdng de xac djnh qua trinh an m d n trong 1 chu 1 ^ Gia t n pH dUoc thUc nghiem la 6,8,10,12,
3, KfT QUA THINGHIEM 3.1 Anh hudng do dm den tdc dd dn mdn ThUc nghiem mau t h e p duoc d d t t r o n g tfUdng d i t Vung Tau, Long An vi C i n ThO.
mau t h i nghiem duoc dat trong mdi trUdng i cd d o am thap la 20%, d 6 pH 6 trong flifiu kierT nhiet dp p h o n g 23 - 27'>C. Ket quS thUc n g h l ^
trinh bay trong Hinh 2, "
6 dp am 20%, c i c m i u loai A cd tdc dfi an m d n nhieu h o n so vdi de mSu loai B d c3 3 dat thuc nghiem. Dieu nSy x i y ra 1^ do c i c loai A tiep xuc hoan toSn vdi mdi trUdng cac tac nhan gSy an m d n nhi^u h o n so vdi
9 2 QBSIEDIfill 10.2015
n i u loai B cd m d t mat tiep xuc vdi mdi trudng chdng khi i m . Ket qu3 cho t h i y trong cdng mdt lifiu kien d d am thi dat Vung Tau cd xu hUdng ]ay an m d n nhieu n h i t la 0.072 mm/nam (loai M va 0.038 m m / n a m (Ioai B), do cd chda luong on d o l i m thuc day qua trinh an m d n dien ra ihanh hon.
Ket quci thUc nghiem tren hinh 3,4 va 5 cho h i y d d i m thay ddi t d 20, 40 va 90% cho giS :ri an m d n khac nhau d c i 3 loai dat. Vdi mdi TUdng d i t Vung Thu thi q u i tinh an mdn cao i h i t vdi d p am 40%. Vdi mdi trudng dat Long
\ n va C i n Tho thi qua trinh an mdn manh Jien ra d dd am 90%, Tuy nhien trong d 3 mdi TUdng thi khi d d i m 90% thi qua trinh an mdn oai B dien ra manh hon so vdi loai A.
3.2 Anh hudng chu ky thay dSi 3& dm den t6c I d dn mdn
Qua trinh an mdn thep trong dat duoc thUc i g h i e m thay ddi theo chu ky khd i m . Ket q u ^ :hUc nghifim sau 12 chu ky khd am dUOc trinh j ^ y trong B i n g 2
B i n g 2. Qua trinh an mdn theo chu ky khd
!m cua d i t Long An
B i n g 3 Dd pH va tdc do an mdn
C h u k y a m 1 2 3 4 5 6 7 8 9 10 11 12
Tdc d d an m d n (mm/nam) Loai A
0.092 0,100 0,155 0.184 0.167 0.147 0.137 0.142 0,201 0,184 0.200 0.191
LoaiB 0.033 0.024 0.028 0.102 0.105 0,101 0 1 0 1 0,112 0.181 0.167 0.159 0,165 Ket q u i thifc nghiem cho t h i y tdc do an ndn cua thip c6 khuynh hu'dng tang dan khi hay ddi c^c chu ky khd i m . Trong 3 chu V.j l i u tien thi qua trinh an m d n d nhdm mau A i n hon nhieu so vdi n h d m m l u B t d 2,5 den 4 In. Qua trinh an m d n difin ra nhanh dfin chu kj h d 9 thi cd xu h u d n g g i i m d i n d nhdng chu ky au, khi d d tdc do an m d n trong n h d m mau A va ihdm m i u B cd g i i t q chenh lech khdng nhieu.
)o dd, q u i trinh thuc nghifim an m d n cCia c i ihdm m i u A va B khdng cd su khac bifit nhieu hi mdi trudng am thay ddi nhanh.
Q u i trinh khd i m Idm cho thay ddi dd am hanh, lam thay ddi mdi trUdng d i t , lam cho u i trinh ein m d n difin ra nhanh hOn so vdi mdi
•udng i m cd dinh. D^y cung chinh Id dac diem nUdng t h i y cda mdi trUdng dat d vung Odng i n g Sdng CCru Long, SUthay ddi do i m thuc te 6 the x i y ra do nhifiu tac nhSn nhU mUa, thdy ifiu, sUxdm ngdp man theo miia. Cac tac nhan dy khdng chl Idm thay ddi d d i m , md bdn thdn d cdn chda cdc hpp c h i t hda hoc phdc tap l i m
Oat
Vung Tau Long An CanTho
p H 6 0.190 0.182 0.131
Tdc dp an m p H 8 0.187 0,152 0,078
dn (mm/nam) p H l O 0.195 0,136 0.156
p H 1 2 0.194 0.185 0.100
Hlnti 6. Anil hudng ciia pH tmng dat Viing T^u
Hinh 7, Anh huimg cia pH trong dat Long An thay ddi do pH. D d pH Id mdt nhdn t d kha quan trpng i n h hudng tdi qua trinh an mdn vat lieu thep, Vi vay can phai xem xet cdc tac ddng cda dp pH den qud trinh dn mon trong mdi trudng dat.
3.3 Anh hudng dd pH den tdc dd an mdn Cie m i u thep lan lutrt duoc tien hanh t h i nghiem trong cac difiu kifin do pH khac nhau.
Op pH duoc cd dinh d cac gia tri 6, 8, 10 va 12 trong cdng mdt moi tfUdng dp am 40%, nhiet d d t d 2 3 - 2 7 ' ' C
Trong dieu kifin pH cd gia tri 6 va 8, q u i trinh an m d n difin ra khd gidng nhau. IMdi trUdng cd qud trinh dn mdn cham n h i t la mdi trUdng dat Can Tho Id 0.131 mm/nam va 0.078 m m / n i m .
Hinh 8, Anh hu5ng cia pH trong dat CanTho Cac mau dat trong mdi trUdng dat Viing Tau cd chieu hudng bi an mdn manh me n h i t Toe dd an mdn lan luot la 0.190 mm/nam va 0.187 m m / nam.
Khi mdi truiJng pH la 10, tdc dd an mdn an mdn trong moi trudng Long An la thap nhat vdi 0,136 mm/nam. Khi mdi trudng dat d difiu kifin pH Ia12 thi dat Can Tho cd tdc d d an mdn t h i p nhat vdi 0.100 mm/nam. Trong tat cd dieu kien pH t d 6-12 thi mdi trudng dat Vung tau cho gia t n a n mdn cao n h i t , Tuy nhien cac giS tri khdng chenh lech nhau nhieu khi pHciJa dat Vung Tdu thay ddi.
Ddi vdi moi trudng d i t Long An v i Can Tho thi khi pH thay ddi, qua trinh an mdn dien ra cd sU thay ddi khac nhau ro ret hon so vdi d i t Vijng Tau.
3.4 Anh hudng chu ky thay doi dd pH den t6c dd an mdn
Khao sat dnh hUdng cua chu ky thay ddi do pH cua mdi trudng Sat den qua trinh an mdn dupc tien hanh b i n g each thay ddi do pH t d 6 dfin 12, ket q u i thUc nghiem dUoc trinh b i y trong Hinh 6,7 va 8.
Trong cimg mdt dieu kifin mdi trudng d i t Vung T i u , ciing chu k^ pH thay ddi thi nhdm mSu A c d x u hudng bi an mdn nhanh hOn nhdm niau B, 6 thdi diem chu ky d i u tifin vdi pH la 6, tdc do an mdn d cd 2 m i u khdng cd sU chenh Ifich nhifiu, Nhung thdi gian t h i nghifim cang lau, tdc d d an m d n cang khac biet nhifiu. d thdi diem cudi dat pH la 12, tdc do an m d n tuong dng cda hai mau nhdm A va B la 0.053 m m / nam vd 0.103 mm/nam. Neu nhUthUc nghiem
l0.20i5QSGg[i;[i2isi93
ve chu ky k h d i m , pH co d m h den qud trinh an mdn cho thay khdng cd sif chenh iich nhieu giCra n h d m m i u A vd B thi chu ky thay ddi pH cho thay su chenh lech ndy 6 mdi trudng dat Vung Tau. Qud trinh dn mdn x i y ra nhanh n h i t d t h d i d n g vdi gid trj pH la 8 - 1 0 , Oieu nay k h i t u o n g d d n g vdi kfit q u i t h i nghiSm cda tdc g i i Osaki [8,9], dng ket luan rSng d d d pH t i f 8 den 10 t h i mau t h i nghifim bi an mdn nhanh nhat, ddc biet la dat cd chifa nUdc bifin,
Trong moi t r u d n g d i t Long An thi qud trinh an m d n co khuynh hUdng tang dan theo chu ky pH 6 n h d m mau B. Nhdm mau A thi cho thay qua trinh an mdn khdng cd sy chenh lech khi chu ky pH thay d d i . Odi vdi mdi t r u d n g d i t C i n Tho t h i qud trinh an mdn cung cd xu hudng tang d i n theo chu ky pH vd dat gid trj Idn n h i t khi pH la 10. Ket qud cung cho thay su chfinh lech an mdn giCfa nhdm A vd 8 cung khdng nhifiu.
Odi vol mdi trUdng d i t C i n Tho v i Long An, qua trinh thay ddi pH theo chu k^ Idm cho thfip bl an m d n trong dat tuy nhifin khi so sdnh cdc gia tri ve an m d n t h i ta nhan t h i y an mdn khi pH thay ddi khdng Idn hon so vdi dn m d n khi mdi trudng am thay ddi.Odi vdi dat Vung tdu thi qud trinh an mdn khi pH thay ddi nhanh lai cho kfit q u i cao, Idn hon nhifiu trong mfli trudng dm, ddc bi^t Id nhdm m l u B
4 KfT L U A N
D d am vd gid tn pH Id mdt nhdn t d quan trpng, gdy dnh hUdng den qud trinh dn mdn vdt lifiu thfip trong cac mdi trUdng dat Vung Tdu, Long An vd Can Tho.
- D d am mdi trUdng dat thay ddi t i f 20 dfin 90% cho qud trinh an mdn difin ra nhanh d ddt Vung Tdu vdi 40% dat 0,276 m m / n d m , vd ddt C i n Tho, Long An d 90% dat 0,1-0,17 m m / n d m . - Chu ky khd am ciing i n h hudng den qud trinh dn m d n , sau 12 chu ky t h i tdc d o dn m d n dat 0 , 1 8 - 0 , 2 m m / n a m cho cd nhdm m l u A vd
TAIUEUIHAMKHAO
[1]. Alain Galerie, Nguyen ^ n Tu (2D0S). An mon va t)io v^
v ^ l i e u . Niia xuat ban Khoa h o c v H y t h u a t [21. Nguyen Van Oiien, Le ^^n Cucmg, Le Biic Bao (2008), Cac giai doan an mon cua thep cacbon thap. Item nhung nong trong ntdi tniong flat. Tap chi Khoa hoc vh Cflng nghe, 3,59 - 64, [JJ.R. Winston Revieand Herbert H, Uhlig (2008), Corrosion and cofTown control. John Wiley & Sons, Inc, Hoboken New Jersey.
[ 4 ] , Pierre - Jean Cunat (2001) Corrosion Resistance of Stainless Steels in Soils and in Concrete. Euro Inox 2002.
[5],A.B.OianceCompany(2003) Step7-Corrosion Guide.
Copynght 2003 Hubbell, Inc.
[6] Mehiin Romanoff (1962) Conosion of Steeling Pilings in Soils. Natniial Bureau of Standards
[71.WaiTenRDgen(2011).Galvani2ed5teel Performance in Soil. Amentan Galvanizen Assodaton, Inc
[ 8 ] . Steel Researdi laboiaiory (2012). Underground CorrosioninJapan JFEStedCorporation.
| 9 ! . Steel Research Laboiatory (2012). Higii Perfonnance Steel f i x Constmction JFE Sted Coiporation.
- Mdi trudng pH dn djnh tai cdc gid tri 6 , 8 , lOva 12 cho t h i y cdtdc d d n g dfin qud trinh an mdn cua thep nhung cie gid t n nay chenh lech khong nhieu, dat 0,1 - 0,2 m m / n d m trong cdc mdi trudng dat khde nhau Qua trinh an mdn cua d i t Vung Tau cho kfit qud cao hon mdi trudng Long An vd Can Tho.
- Moi trudng pH thay ddi lifin tuc theo chu ky tif 6 den 12 cung dnh hUdng den qua trinh dn m d n . Qua trinh an mon manh mfi dat dfin 0,56 m m / n d m trong mdi trudng d i t Vung tdu vdi nhdm m l u B. Do 66. khi siir dung c i c c i u kien thfip tai v d n g d i t cd chda nudc bifin c i n cd sUquan tdm dfin mdi trUdng pH cua dit.Tai c i c viing Odng B i n g Sdng CdU Long thi c i n quan tdm dfin d o i m cao cda mdi trUdng d i t .
9 4 Q S a i E [ I Q l 10.2015 I I I I I I I I I I
