drzee-soilcorrosivitynace
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Soil Corrosivity andCorrosion Control
Dr. Zamanzadeh (Zee)
Geoff Rhodes
Matco Services, Inc.Octoer !th, "##$
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O%tline
&' Introd%ction
"' Soil Characteristics
' Soil Corrosivity
' *arameters effect soil corrosivity
+' Soil corrosion rate
' Corrosion Ins-ection
' Corrosion Control
!' Cathodic *rotection
$' / 0 1
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2istory&34arly Cent%ry' all corrosion -rolems 5as attri%ted to stray
c%rrents from trollly cars, and s%5ays.
"3&$ con6ress a%thorized 78S(7ational 8%rea% of Standards toinvesti6ate stray c%rrent -rolems
38y &$"# they fo%nd o%t that yo% do not need to have stray
c%rrents to have corrosion -rolems
3&$+ 78S concl%ded that soil corrosion is too com-le9 to -ermitcorrelation 5ith any one -arameter. 49tensive data 5as -rovided at
this time for many soil conditions and metals
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Predicting Soil Corrosivity
7at%ral Reso%rces Conservation Service
&$ e9tensive soil testin6 -erformed on over
",## soil ty-es in :nited States
Soils descried y horizon (layer), str%ct%re,
color, or6anic content, -2, 5ater tale,
to-o6ra-hy, and chemical;mineral content.
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Predicting Corrosivity of
Soils:tility =o5ers, *oles,
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Why Do We Need to Predict Soil
Corrosivity?
4arly corrosion -revention
S-ecify coatin6s, cathodic -rotection, or
alternate materialsS-ecify ins-ection and maintenance
intervals for %ried str%ct%res and %tilities
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Soil Chemistry1- Mineral soils are a group of primarily inert
combinations of oygen! aluminum! silicon! and
iron "and other metals#$
%- &he primary constituents of over '() of soils are*
+ Poly silicates* "Si,
'
.-# / 0! l! or Na
+ rthosilicates* "Si..-# / 0!2!3!Ca! 4e! or
+ Metasilictes* "Si,%-# / Ca! Mg! 5$
+ ides* "Si%! 4e%,! 4e,.#
+ Calcite* "CaC,#
+ 2ydrous luminum Silicates "Clays#* "l 2y# "Siy#
,- rganic matter is another constituent
.- Corrosive 6onics* Chlorides! Sulfates! Sulfides
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What 4actors ffect Soil
Corrosivity?
@ Chloride level
@ Moist%re content
@ O9y6en content;Redo9 -otential
@ Soil -ermeaility;te9t%re
@ -2;1cidity @ =em-erat%re
@ Soil resistivity
@ Draina6e characteristics@ S%lfate and S%lfite ion concentrations
@ Microiolo6ical activity
@ Stray c%rrents, 4lectrochemical *otential Aields
@ S-illa6e of corrosive s%stance;-oll%tion
3 16ric%lt%ral chemical activities
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Soil &esting + Soil Classification
Classification -er 1S=M D"! 0 D"!!
Soil str%ct%re'
Gravel (Coarse -articles @ retained on B sieve)Sand (Coarse -articles @ retained on B"## sieve)
Silt 0 Clay (Aine -articles @ -assin6 B"## sieve)
Color
Star7 color changes indicate reducing soils
Dar7 colors indicate organic matter
3ight colors indicate mineral leaching
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Soil &esting + Soil Classification
Odor
Or6anic smells may indicate iolo6ical activity
S%lf%ro%s smell may indicate microiolo6ical activity
@ -artic%larly anaeroic acterial activity
*lasticity
2i6h to moderate -lasticity indicates hi6h 5ater
holdin6 ca-acity o5 -lasticity indicates -oor 5ater holdin6 ca-acity
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Soil &esting + Soil Classification
Structure: Clay + siltColor: Homogenous, darkbrownOdor: Slightly organicPlasticity:High
Corrosivity: Moderate tolow depending on ioncontent & pHlater found tohave neutral pH and lowchloride content; lowcorrosivity
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Soil Characteristics (clay and sand)
1- Clay has the finest particle si8e 9hich reduces movement of air
"oygen# and 9ater! i$e$ lo9 aeration 9hen 9et$ &his may lead to
very lo9 general corrosion! but increase local "pitting# corrosion by
setting up differential aeration cells$
%- 2o9ever the high plasticity "stic7iness# of clay during shrin7-s9ell
of the soil can pull off susceptible coatings$
,-Clay also is susceptible to crac7ing during 9et-dry cycling 9hich
can help transport air and moisture do9n to the pipe surface$
.-Sand promotes aeration and moisture distribution$ Soluble salts
and gases "air:oygen# can are more easily transported to the
metal surface$ &his may lead to greater general corrosion but also
produce less pitting$
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Soil Classification per ;SCS
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Soil &esting
Soil Resistivity =estin6'
In3Sit% Soil Resistivity @ 3*in
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Soil &esting
In3Sit% Soil Resistivity =estin6
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Soil &esting
aoratory Minim%m Soil Resistivity =estin6
E+## ohm3cm 49tremely corrosive
+##3&,### ohm3cm Fery corrosive
&,###3",### ohm3cm Moderately Corrosive ",###3,### ohm3cm Mildly Corrosive
,### ohm3cm *ro6ressively lo5er corrosivity
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&!
Color and 1eration
2i6h levels of acteria can cons%me the
o9y6en -resent in the soil
8acteria Cons%me O"*oor 1erated
2ot3di- 6alvanized steel 5ill not -erform as
5ell in soils containin6 lar6e amo%nts of
or6anic acteria
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&$
=ime of
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"#
*article Size
Controls aeration and time of 5etness cate6ories of -article size for soils
Sand (#.# 3 " mm )
Silt (#.##+ 3 #.# mm)
Clay (E #.##+ mm)
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"&
Color and 1eration
Sim-lest method of characterization Red, ello5 and 8ro5nO9idized Ae
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/%estions to e asJed
Does corrosion ta7e place?
6f it does! ho9 fast? 3ife epectancy?
2o9 can 9e control the rate of corrosion?
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Immunity, Cathodic Protection
Corrosion
tability Diagram For Iron
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Soil &esting +
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Corrosion Rate
=est co%-on
Resistance *olarization
=afel a5Dynamic *olarization
4IS
*hysical Meas%rements
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Aail%re 49am-les
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:tility, Comm%nication =o5er
Str%ct%res
1nchor Rods
Galvanized *oles and =o5ers
Co--er Gro%ndin6
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CS
raphiti8ation*Cast 6ron Water Main
@rittle 4ailure
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*hoto6ra-h sho5in6 the lon6it%dinal cracJ
in the -i-e.
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*hoto6ra-h sho5in6 the transverse sa5 c%t thro%6h the
-i-e at a location &+ inches from the end of the -i-e
Corrosive soils, Clay, 2i6h Salt Content Soils and MIC lo5 -2
*h t h h i th t d
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*hoto6ra-h sho5in6 that secondary
cracJin6 5as confined to the corroded areas
of the -i-e.
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More Aail%res
Aail%re of =o5ers in flooded valley, "##&
Similar incident in 8C "##"
Aail%re of anchor rods "##
Aail%re of anchor rods "##+
2i6h chloride content 0 lo5 -2Fery hi6h chloride content 0 hi6h -2
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ocalized Corrosion 1ttacJ at a load earin6 memer
Direct 8%rial :tility =o5ers
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49tensive ocalized Corrosion
S%s-ect *otentials
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Galvanized 1nchor Rod
1ove Gro%nd
:nder6ro%nd
Co--er Gro%ndin6
Soil 4nvironment
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Corrosion
Galvanized 1nchor Rods
Aail%re
Corrosion
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Shiny vs. D%ll
Galvanized Steel
G l i d St l
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Galvanized Steel
A%ndamental Mechanisms
8arrier
Cathodic *rotection
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Methods of *rotectin6 Iron and Steel
8arrier *rotection Isolates metal from the environment M%st adhere to the ase metal M%st e resistant to arasion
Cathodic *rotection Chan6e electrochemistry of corrosion cell 8ased on the electrochemical series Ins%re ase metal is the cathodic element
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Staility of Galvanized Steel
O9y6en,
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Zinc (6alvanized)
Staility
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I7S*4C=IO7 of =o5er Gro%nd
1nchors
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OKectives of Ins-ections
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Ins-ection =echniH%es
Fis%al
49cavation and Fis%al Ins-ection
7on3destr%ctive techniH%es(so%nd, 4M>)
4lectrochemical =echniH%es
DesJ St%dy
=ier =estin6 Ins-ectionAreH%ency of Ins-ection
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49cavations33Sho%ld I Di6("ft)?Common Industry Practice
7e6ative Aactors aor intensive Inherently dama6in6 InadeH%ate vis%al e9amination Safety com-romised d%rin6 fill removal =renchin6 re6%lations
Diffic%lt to re-eat
1 h R d C i
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1nchor Rod Corrosion
Scenarios
Corrosive Soil or 8acJfill
Galvanic effectsStray C%rrents
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Corrosion of 1nchor Rods
Determine -resence of active corrosion' 2i6hrisJ areas
Determine a--ro9imate corrosion rate
S-ecific recommendation'
a) Immediate action'& to 3 + to years
) 7o action, Cathodic *rotection 0 Coatin6,
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Lno5led6e 8ased Ins-ection
1 Jno5led6e ased assessment -lan is critical to an effective andaffordale asset mana6ement -ro6ram.
Lno5led6e 8ased Ins-ection can identify the most criticalcom-onent(s) ased on o-eratin6 stresses and corrosionmechanism (s)
=o ens%re that they are maintained at a condition aove the criticalthreshold
8enefits of Lno5led6e 8ased
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8enefits of Lno5led6e 8ased
Ins-ection8y eliminatin6 ins-ection tasJs that
contri%te little to risJ mana6ement and
miti6ation
Defines c%rrent condition
Deterioration rate
*erformance reH%irements
Reliaility thresholds
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Ins-ection
*hoto6ra-hic doc%mentation*otential meas%rementsSelection of anchor rod*hoto6ra-hic doc%mentation*otential ma--in6Soil resistivity meas%rements de-thsGeneral Oservations' Gro%ndin6 iss%es, corrosion oservations, -aint -rolems,site -rolems, mechanical dama6e, concrete -rolems and corrosion in concrete
49cavationDimension 0 coatin6 meas%rementSoil testin6' dry and 5et, corrosion rate, ZR1>.Com-%terized data entryRevie5 y team leader, Matco -roKect mana6er and Dr. Zee
Recommendations' Re-air, Re-lacement or no action. Cathodic *rotection
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*hoto6ra-hic Doc%mentation
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8: B !"##+
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!##"+!##"+ .N*G
http://k/870025/870025%2047.JPGhttp://k/870025/870025%2047.JPG -
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=estin6 -er 1S=M G&
Will determine native potentials of copper,
steel, and zinc in the soil near the anchor.
Will determine mixed potential and
corrosion current between copper-steel and
copper-zinc when coupled in moist soil.
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Soil Resistivity
4-pin Wenner method per S!" #$%
&ins spaced at 'ft and ()ft *spacing + a
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1dditional Data
Dry and sat%rated soil resistivity in the la
ZR1
Corrosion rate
Soil sam-les
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Recommendations
*erform soil resistivity and electrochemical -otential
Determine 6alvanic corrosion rateRate the corrosion attacJ ased on the aove-erformance -arametersDetermine electrical contin%ity and 6ro%ndin6Desi6n C* -er 71C4 Standards4stalish criteria for acce-tanceC* sho%ld e desi6ned y 71C4 CertifiedCorrosion S-ecialist and meet 71C4reH%irements
Considerations for 1--lication of
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Considerations for 1--lication of
Cathodic *rotection*otentials more nole than 3#.#Corrosive soils16e years
Soil resistivities E +### ohm3cm
Galvanic c%rrent "## to +## micrometersCl &+# --m*resence of stray c%rrents, interfernce or e9tensive co--er 6ro%ndin6
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S%mmary
=he corrosion eval%ation -rotocol sho%ld e ased %-oncorrosion en6ineerin6 f%ndamentals and -rovides a aseline for f%t%re ins-ection
=he a--roach can e a--lied to all ty-es of soilformations