CP 3 - Quiz 1 1.
Version : A
What would be the potential of pure iron to
a standard
hydrogen electrode if the Fe ++ activily is 0 .1
Moles/liter (assume T:'2730K )
RT Em = Emo+ IIF
{JI.QJ. I
ro
8~.:.J.:;I.\,·2:.c7.:3 -, .. 1
= -0 .44 V SHE +
2x96.500
= -0.44 V SHE + {(0.01 18V x (-2.303))
= -0.44 V
x
SHE -
-41 3 mV SHE
B.
-440 m~SHE -467 mVSHE +467 mVSHE
c.
SliE
The Pourbaix Diagram predicts corrosion by relating the following faClors.
x
A. B
c D. 3.
=...().467 V
A.
D.
2
0.027 V
Potential across a me tal interface and pH Open circuit potential o f the anode compared to the open ClrCliit pOlenlla l 01 the cathode Closed circuit potential of the anode compared to the closed circUli potential of the ca thode The length o f lime for a known amount 01 curren t
According to the EMF series, which material(s) could be used as a ga lva nic Llnode rnat en
I. Magnesiu m 11. Zinc III. Iron IV. Aluminum
x
January 2007
A.
I only
B. c.
1& 11 only I. II & III only
D.
I, II , II I & IV
Upda ted Ap t 2009
4
If the references used in the following potential measurements are at 25°C, vihich one(s) are equivalent to -9 12 mVCSE'- ? I. -596 mV ~I,E II. -862 mVssc(SJ) III. +204 mVZ re
IV. -857 mVsce A. B.
x
C
o 5,
Which one of the following would result in the largest corrosion rate accord ing to Faraday's Law '
B.
2 A discharge current density of 1OmAlft from a steel plate 2 A discharge current density of 61-lAlcm from a lead plate
c.
A discharge current density of 100 mAJm 2 from a zi nc anode
D.
A discharge current density of 10l-lNcm
A.
x
6.
I only I & III on ly II & IV o nly I , II & IV only
2
from an alum inum anode
An increase in corrosion rate in a corrosion cell could be caus ed by which of the fo ll owing?
L increase in metal ion concen tration at the anode II. decrease in ion concentration in the electrolyte
III. increase in cathode polarization IV . increase in AC current density
A B C
o
¥
7.
IV only I & III only 1\ & IV only I, III & IV only
Which of the following satisfies the -850mV cse @ at 25°C? I. A potential of -864 mV with respect to a copper sulfate reference electrode @ 40°C.
II A potential of -823 mV w ith respect to a copper sulfate reference electrode @ -SOC . III. A potential of -746 mV with respe ct to a saturated s ilver chloride refe rence electrode @_ ' IJ) 1S0C. IV. A potentia l of -785 mV w ith respect to a saturated calomel referen ce electrod e @
1...> ""1.-':1"\1,,,, ~-,R
0 40 C.
X
8.
A
~.
II only
D.
I.II .III&IV
: ~""&O~Yo,,y
G, '"lL~::?
~
~
SA\i:~T~I..
fJ..-J.7',-s--.-...~
<-U
\
~ ~
L~L~~ ~ <~ I
Convert -880 mV/SCE io the equivalent mVfcs (?
x
A.
B.
c. D.
January 2007
-952mVlcSE -80SmVf cSE +995mV/CSE +805mVfcSE
Updated Af ri l 2009
CP 3 1
QUI Z
2
Ve rsio n: A
Center connected anodes are recomme nded to
A
8 x
C
o 2
Improve COl1 nectlo n resista nce Im prove c urre nt density on anode surl ace Improve utilization of the anode reduce costs
Ca rbon ba ckfill is placed aroun d a. n im pres sed current anode 10 I. Decrcas the resistance to earth 11. Limit gas btocka.ge Itl. Increase anode life IV. Decrease drying out of the soil lnterf8cc A
,
B C
o
3.
A B C
D
to reduce the overall CirCUit resista nce 10 provide constant current under vi-ln<.lole CirculI 10 redu ce power consumption 10 1IIllIt electroosm osis
reSI~l <~nce CO ~C lt l() (1S
In a cathodic protection systern electrolysIs of w ater w ould be mosl lI"ely
,
A 8 C
o 5.
I. II . III . IV II & II I o nly
TIle princi ple reason to use a consta nt curren t rectifier is
, <1
1 only I. II & II I only
as the pnmary cathod ic reac tion on a steel pl;Jelim: If', a ,ow p H sOil on em im pressed curre nt anode in neut rat so ils o n the a ca thod ica lly protected steel pip eli ne :n so;1dy soi l at low currelli oulp Is on ;)n Impressed current anode in sea water
Galvamc anodes purchase d for soil applications are commonly prepackaged In 3 cllemlcal back ill to I. Prevenl an ode passivat ion II. Retai n m oisture III . Im prove contact resistance with the earth IV Promote tile formation o f IIlsolu bl e sulfa te compounds
,
A B
C
o 6
IV onl y I, II & IV only I, II & III only I, III & IV only
Which of the foll owing l ake s pl ace fo r
,
Ja nuary 2006
A B
C D
1 he The The The
eff ect l v(~
cathod iC protec tion ?
ca thodes are polafl7.CcJ m orc positive 10 opeJI c'rC:1I11 anooe potential anodes are polarized more negative 10 the open Clrcun cathode potenua t cathodes are polarized more nega tive 10 tile open ClrCUI, anode potential anodes are polarized more positive to Ilw oile r; cl rcu!l ca tt,o(lo poten l l3l
7
T he primary purpose of gypsum in a Q3 1v3n ic anode backf ill J118ter ial is to which of the following iO lls?
A B x
8
C D
A B C D
ce of
o~
i he follcw ing"7
equilibr ium potent ial exchange current dens it y a node potential corros ion p otential
If til e cu rren t density of a magnesium anode is 10 fJ Aicm ' , wll::.l1 is the Zl noo e eff iCi en cy?
A. x
10
,1[1 c1bunaa
Carbonates Bicarbo nates Sul/ ates Phosplla tes
T he ra te of a specific cat hod ic protectio n rea ction depencJs pmnzm ly on v/h icn
, 9
~; up p ly
B. C D.
88% 50% 28% 12%
If 8 50 meter di ameter above gro und , steel ta nk is el ect rica lly grou nded ground ro ds. the anticipa ted effect(s) wo uld be wh ich of the ;01l0\.. . 'ln9"7
Oil
four sid es uS ing co per clad
Sig nifica nt reduction In grounding reslstcHlce for the ta nk II Sig nificant Increase In cCl\ hodic protection cu rrent req uirement III Sign ifican t shift in the corrosion potent ial of the tank IV. Insig nificant sh ift in the corros io n potentlZlI of the tan k
x
A B C D
I & II on ly IV only I, ll & III 1. 11 & IV
, 11
For a curren I dens ity of 1A1m discharging from an impressed current anode In fre sh water. w t ic h of the following anodes would have the largest we ight loss?
x
A
B C
D 12
The current capaCity of an alumi nu m sacrifi cia l anode IS the LE AST for INhiCh of the fo ll OWing o ndl tlons"
x
13
Graphite High sil ico n cast iron M ixed me!3 1oxide Platinum clad niobium
A
Anode curre nt density 100 mA!ft 2 in sea water
B. C
Ano de cu rr ent density 50 mA/ft2 in sa lin e Ill ud Anode cu rrent density 20 mAJft2 in sea w aler
D.
A node curre nt density 600 mNft2 in br ine
With activation polarization controlling, time is req uired for polari zat ion to es tCl tJ lish upon appli ation of CP curren t because A B
x January 2006
C
o
charge cannot move within the electrolyte Irlstanl ly Ions cannot move within the electrolyte ins tan tly. charge cannot move across the interface ins ta ntl y. charge ca nnot move within the metal ins tantly
Version: A
CP3 - Quiz 3
Wh ich one of tl, e fo llowing e lectrica l Interference situations causes oe letenous t:lfcc ts ')
x
2.
Stray DC current pick-up on
8
A stray AC current density of < 2 rnA/crn on steel A stray current discharge from a cast iron pipe A polarized potential on steel shifted from -1 080 mV CSE to -
C
o ~
8 C
D
8 x
C
D
Electromagnetic induction Conductive couptlng ElectrostatiC Ind uction Power-fol low through an ionized path
The magnitude of the rise in earth potential 81 some pOint "x" from a ve rtlCa ll:l1p~csst:w current a ode IS ~
x 5
is less effective than a forc ed drainaue bond In rnitigali;-Jg ~ nlc rfcrcnce suppl ies a current that is equal and opposite 10 the interference C;Jrrenl drains 100% of the interfering current has 7ero resis tance
Which of the following circumstances will NOT result in AC interference on an underground pipe Ine parallehng an /\C powerhne?
A.
<1.
steel pipe
A rever se current SWitch composed of diodes
x
3
a bare low carbon ,
A
8 C D
independent of the locahon of '·x'· Inversely proportional to soil resistivity Inversely proportional to anode Cl)l"rent. inversely proportional to anode I(!n gth
The rnagn!lude of the Induced /\C voltage on a pipeline paralleling an AC powcri111() IS I directly proportionat 10 the phase current magnitude . II Inversely proportional to the plpeline-Io-phase conductor distance 111 directly proportional 10 coaling conductance . IV directly r "oportionai to ttle relative Imba lance in the phase conduc:o r.
x
6
~
I only
8
II & III only I, II , IV only II. HI , IV only
C D
The mag nitude of geornagnetically Induced VO ltage on a lJipeline IS
I. d irectly proportional to coating resistance 11 inversely proportiona l 10 pipe length . 111. dependent on Ihe pipelines location relative 10 the geornagnetlc poles IV. vanes with tnne of day.
A B C
x
Janua ry Z007
D
I only I & II on ly til & IV only I. III & IV only
What is the toterab le step voltage for a 70kg person walking on 5000 otlnl-Cm soil if the fault d ration IS 0.5 sec?
7
A. B C D
x 8
What
IS
6880 V 1887 V 532 V 288 V
the safe separation distance between a metal tower leg and a sled pipel ine :n 110,00 ohm-cm
so il if th e fault current is 18 kA?
x
A B
c. D 9
Which of the followin g situations would AC corrosion NOT be expected on a cZlthocically prot pipeline? (see Equation 3- 18) A. Vac :=' 5V,A I\=lcm 2 . p=10 0 -m
led steel
,
10 V; Ar.::.10 cm' p = 500 O-cm
D
10 .
6.61 m 10.2 m 60m 189 m
2 Poi nts What IS the maximum AC current thai a 70 kg human body can lolera(e if tl,c shock durati on I 2 seconds? A
x 11
1.S7A 1. 16A
8 C
aOSA
D
O.11A
,
If an ac stray current dens ity exceeds 100 Nm at a ho li day. the best sol<..l lio n 10 avoid corroSI n problems is A
8
x
January 2007
C D
increase the ca lhodic protec tion curre nt densities . coal the holiday. provide ac grounding for the structure al13ch an alu m inum a nod e al the ho liday location
Version: B - May 007
CP 3 - Qui z 4
C alculate the res istance 01 15 vertica l surface anodes given the following : Anode diameter :. 7.6 cm Anode le ngth :. 1.52 m Carbon d iamete r :. 25.4 em Carbon length :. 2. 13 m Soil resistivity = 3500 oh m ·cm Spaci ng 4 .57 m
1.
=
2.
Calcu late the resistance of 15 horizontal anodes g iven the fo llowing mlormaTlon v'lIth a depth 01 1 loot: Anode diameter 0:: 7. 6 cm Anode length = 1.52 m Carbon dia meter = 25.4 em Carbon length :. 2. t 3 m Soi l resistivity = 3500 ohm -em Spaci ng 4.57 m
=
3.
Calculate the life of a 17 Ib mag nesium anode wilh a current output o f 100 mA assuming an av rage anod e current den sity of 40 m a/ft2. Ut ili zation factor 1.0 .
4.
Calculate the life of a 17 Ib magnesium anode with a curren t output of 100 mA a ssuming an av rage anode current density of 5 ma/H2 . Utilizatio n fact or 1.0
5.
A 10kg high potential m agnesium anode has an open Circu it potential of 1 75V c5E ' It is conne ted to a coated pipeline resulting in a polarized po tentia l of -0 .980 V CSE ' Assum ing a total Circuit reslsdnce of 10
n , an anode efficiency o f 35% and a utilization
facto r 01 0 .9 , calcul ate tr:e servic e lite 01 the
a~Ode
6.
Given a 0.3m (12 in) d iam eter. 32 19 meters (2 mile) long coated pipeline th
7.
W hat is the estim ated current required to protect a bare steel pipe 10.75 ill OD and 10.000 fee long that is in cl ay soil (1800 0 cm ) lor 7,5 00 feet an d aerated sandy soli (60 ,000 0 cm ) for 2,500 II?
A x
B. C.
o
8.
49A t43A 3.5 A 13 A
What is the approximate c oated area of steef in 10000 ·em soillhat has pS/m 2 ?
A. B. C x
o
0.006% 0.06% 99 .940% 99.994%,
Question #9 on back
May 2007
a coating
conductanc of 100
9.
Which of the follow ing methods in estimating current requ irements for the calnodic protection of a coaled structure contains an incorrect relationshrp? A.
Assum e a specific coating resistance (r'c) calc ul ate total su rface area (A ); assume a minimum of 300 mV shift is needed across the coating:
/ req'(/=
300 mV. A ' , r ,
calculate B.
Assume a min imum current density (lcp ) for coated surface: calculate lotal surfac area (As): Calculate
c.
r req' d
= i
A
,
IlEp - - - >0 Measure ECOff and apply a test current (II): measure Ep with time ur11 il III 'd lOOmV I req = IT (Ep - 1':",,, ) Calcu late
x D.
Apply a test current (It); measure t:.Vslr (Von - Voll) 10 remote ORrlh·
Jreq'd = Calculate
May 2007
IlY
I STR
O.3V
T
CP
3~Qu iz
5
Version: A
----- ----- ----------~-~ ..
1
A
c~lhod i c
x
A
10 determinc 1I1C corrosion ra le of steel
B
to 1l1eaSure a polarized potential re presentative of a \ioll(iay to determine the corrosion potential of a structure only under stray current co nditions .
C D 2
protection coupon is used
The fa lIowin ' chanqcs were recorded in a m S9nes iuIll anode sl'.stem . Current output 100 rnA to 63 mA Pipe on-Dotential -1.100 VC:SE to -0 900 Ves= Anode polarized otenl131 -l .7V cs [ IO - 1.2SV:· Sl
--j
Which of the following factors could be respo nsible? I. failed electncal isolation II. increase coating damage III. anode polarization IV . decrease in so il moisture A
x
3.
B C D
0 If the potential of -700 mVCS( IS measured with the reference at 2S C . what is the mctlsured pOlentlall! the reference is al 40 0 C? A C
-686 III V cs::. -700 mV cs (. -714mV CSE
D
-868 mVCSL
B x
4
What i$ the measured potential if the true potential is -900 mVCSE . th e resistance of each teslle d IS 010. the pipe-to-earth resis tance is 2 0, the reference electrode contact resistance IS 200 kO and ttl meter resis tance IS 1 MO?
x
A
B C 0 5
I only III only ) & IV only II. III & IV only
-750 mV CSF -867 mV CSE -900 mV'SE -1080 mV CSE
What is the true po ten tial if the meas ured potentia l is -900 mV CSE . the r0.s'.s t ~~r I CC of cac ll test Ie dis 0 .10 . the plpe-ta-earth resistance IS 20. the reference electrodp. contact reslst ~,'\Ce IS 200 kO and th meter resistance i.- 1MO? A
8 C
x
January 2006
0
-720 mV,s!: -867 mV CSL -900 mV CSF -1080 mVCSE.
6.
Witho ut know ing the Impedance characteristics of th e cathodic protect ion CI'CIIll. t"l' Zl:)propr I3 -, time af ter interruptio n to accept an Instant off pole nhal IS which 01 the lollowin\p 1\
,
o C D.
7.
10 milliseconds
0.3 seconds 5 seconds
What IS the percent DECREASE of cu rrent in a galvanic an ode circuit th at 11(:15 a resis tance of structure pot ential of -1000 rnV CSE and an anode potential of -1100 mVcsr- if <.I n fl mmctc r With Internal circuit is added to meas ure the current?
,
A
8 C D
8,
3 micrOSCCQIllJs
1% 11% 25% 89%
W hic h of the following conditi ons w ill increa se 9fl lvanic anode polclfl zation')
I. increased ag itation n II. decreased M • io ns III . decreased temperature IV. decreases surlace area
, 9.
A B. C D
I only I & II only III & IV only 1. 11.111 & IV
How long dUring Ihl s 30 day pe riod has th e rectifier been OFF g iven DC out~.Jt 15 Vdc and 10Adc 4 rev per minu te on a KWH mei er where K :: 1 AC power consumption for the 30 day period is 120 KWH
,
A.
o days
B
9 days 12 days 21 days
C D
January 2006
[ h(~
fOllOWing data ?
o. a 0 50
