corrosion prevention 316.ppt

8/16/2019 corrosion prevention 316.ppt

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CORROSIONCONTROL

MATERIAL SELECTIONALTERATION OF ENVIRONMENT

PROPER DESIGNCATHODIC PROTECTION

ANODIC PROTECTIONCOATINGS & WRAPPING


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(1) MATERIAL SELECTION (selection o !"o!e" #$te"i$l o" $

!$"tic%l$" co""osi e se" ice)

Metallic [metal and alloy]

Nonmetallic [rubbers (natural and synthetic),

plastics, ceramics, carbon and graphite, andwood]


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Metals and Alloys

No En i"on#ent P"o!e" #$te"i$l

1 Nit"ic $ci' St$inless steels

C$%stic Nic el $n' nic el$llo*s

+ H*'"o,%o"ic $ci' Monel (Ni-C%)

. Hot /*'"oc/lo"ic$ci'

H$stello*s (Ni-C"-Mo) (C/lo"i#ets)

0 Dil%te s%l %"ic $ci' Le$'


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No En i"on#ent P"o!e" #$te"i$lNonst$inin2$t#os!/e"ic

e3!os%"e

Al%#ini%#

4 Distille' 5$te" Tin6 Hot st"on2 o3i'i7in2

sol%tion Tit$ni%#

8 9lti#$te "esist$nce T$nt$l%#1: Concent"$te'

s%l %"ic $ci'Steel


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E;2 < St$inlessSteels

Stainless steels areiron base alloys thatcontain a minimumof approximately

! "r, the amountneeded to pre#entthe formation of rust

in unpollutedatmosphere$wt$! "r

% i s s o

l u t i o n r a t e ,

c m

& s e c


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Allo*in2 ele#ents o st$inless steel<

Ot/e" t/$n Ni= C" $n' C= t/e ollo5in2 $llo*in2 ele#ents#$* $lso !"esent in st$inless steel< Mo= N= Si= Mn= C%=

Ti= N>= T$ $n'?o" W;

M$in $llo*in2 ele#ents (C"= Ni $n' C)<

1; C/"o#i%# Mini#%# concent"$tion o C" in $

st$inless steel is 1 -1.5t;@ St"%ct%"e < CC ( e""ite o"#in2 ele#ent)

B Note t/$t t/e $ nit* o C" to o"# C"-c$">i'es ise"*

/i2/; C/"o#i%# c$">i'e o"#$tion $lon2 2"$in>o%n'$"ies #$* in'%ce inte"2"$n%l$" co""osion;


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in$"* 'i$2"$# o Fe-C"

Si2#$ !/$seo"#$tion 5/ic/

is initi$ll* o"#e'

$t 2"$in>o%n'$"ies /$s to>e $ oi'e'>ec$%se it 5illinc"e$se/$"'ness='ec"e$se '%ctilit*$n' notc/to%2/ness $s 5ell

$s "e'%ceco""osion


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; Nic el

St"%ct%"e< FCC ($%stenite o"#in2ele#ent?st$>ili7e $%stenitic st"%ct%"e)

A''e' to !"o'%ce $%stenitic o" '%!le3 st$inlesssteels; T/ese #$te"i$ls !ossess e3cellent'%ctilit*= o"#$>ilit* $n' to%2/ness $s 5ell $s5el'-$>ilit*;

Nic el i#!"o es #ec/$nic$l !"o!e"ties ost$inless steels se" icin2 $t /i2/ te#!e"$t%"es;

Nic el inc"e$ses $ %eo%s co""osion "esist$nce o#$te"i$ls;


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Ternary diagram of Fe-Cr-Ni at 650 0 and 1000 0C

AISI : American Iron and Steel Institute


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Anodic polari ation cur!es of Cr" Ni and Fe in 1 N# $S% & solution


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Influence of Cr on corrosion resistance of iron

'ase alloy


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Influence of Ni on corrosion resistance of iron 'ase alloy


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Influence of Cr oniron 'ase alloycontaining ()*-

+)(,t) Ni


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+; C$">on

Ve"* st"on2 $%stenite o"#in2 ele#ent (+:3#o"e e ecti e t/$n Ni); I;e; i $%steniticst$inless steel 16C"-6Ni cont$ins :;::4@C=its st"%ct%"e 5ill con e"t to e""itic st"%ct%"e;Ho5e e" t/e concent"$tion o c$">on is%s%$ll* li#ite' to :;:6@C (no"#$lst$inless steels) $n' :;:+@C (lo5 c$">onst$inless steels to $ oi' sensiti7$tion '%"in25el'in2);


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Mino" $llo*in2ele#ents <

M$n2$nese

A%stenitic o"#in2 ele#ent; W/en necess$"* c$n >e%se' to s%>stit%te Ni; Concent"$tion o Mn in st$inlesssteel is %s%$ll* -+@;

Mol*>'en%#

Fe""itic o"#in2 ele#ent; A''e' to inc"e$se !ittin2co""osion "esist$nce o st$inless steel ( -.@); Mol*>'en%# $''ition /$s to >e ollo5e' >* 'ec"e$sin2

c/"o#i%# concent"$tion (i;e; in 16-6SS /$s to >e'ec"e$se' 'o5n to 1 -16@) $n' inc"e$sin2 nic elconcent"$tion (i;e; /$s to >e inc"e$se' %! to 1:-1.@);I#!"o es #ec/$nic$l !"o!e"ties o st$inless steel $t/i2/ te#!e"$t%"e; Inc"e$se $ %eo%s co""osion"esist$nce o #$te"i$l e3!ose' in "e'%cin2 $ci';


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T%n2sten Is $''e' to inc"e$se t/e st"en2t/ $n' to%2/ness o

#$"tensitic st$inless steel;

Nit"o2en (%! to :; 0@)St$>ili7e $%stenitic st"%ct%"e; Inc"e$ses st"en2t/ $n'

co""osion "esist$nce; Inc"e$ses 5el' $>ilit* o'%!le3 SS;

Tit$ni%#= Nio>i%# $n' T$nt$l%# To st$>ili7e st$inless steel >* "e'%cin2 s%sce!ti>ilit*

o t/e #$te"i$l to inte"2"$n%l$" co""osion; Ti$''ition 03@C; T$ N> $''ition 1:3@C;


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Co!!e"Is $''e' to inc"e$se co""osion "esist$nce o

st$inless steel e3!ose' in en i"on#ent cont$inin2s%l %"ic $ci';

Silicon

Re'%ce s%sce!ti>ilit* o SS to !ittin2 $n' c"e iceco""osion $s 5ell $s SCC;


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Infuence o alloying elements onpitting corrosion resistance o

stainless steels


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Infuence o alloying elements oncrevice corrosion resistance o

stainless steels


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Infuence o alloying elementson SCC resistance o stainless

steels


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!uple" #austenitic $ erritic% /$s en/$nce'"esist$nce to SCC 5it/ co""osion "esist$nce !e" o"#$ncesi#il$" to AISI +1 SS; H$s /i2/e" tensile st"en2t/s t/$nt/e $%stenitic t*!e= $"e sli2/tl* less e$s* to o"# $n'/$ e 5el' $>ilit* si#il$" to t/e $%stenitic st$inless steel;C$n >e consi'e"e' $s co#>inin2 #$n* o t/e >est

e$t%"es o >ot/ t/e $%stenitic $n' e""itic t*!es; S% e" $loss i#!$ct st"en2t/ i /el' o" e3ten'e' !e"io's $t /i2/

te#!e"$t%"es $>o e +:: : C;

&recipitation 'ar(ening - H$ e t/e /i2/est st"en2t/>%t "e %i"e !"o!e" /e$t-t"e$t#ent to 'e elo! t/e co""ectco#>in$tion o st"en2t/ $n' co""osion "esist$nce; To >e%se' o" s!eci$li7e' $!!lic$tion 5/e"e /i2/ st"en2t/to2et/e" 5it/ 2oo' co""osion "esist$nce is "e %i"e';


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Stress Corrosion Crac)ing o StainlessSteel

St"ess co""osion c"$c in2 (SCC) is 'eJne' $sc"$c n%cle$tion $n' !"o!$2$tion in st$inlesssteel c$%se' >* s*ne"2istic $ction o tensilest"ess= eit/e" const$nt o" sli2/tl* c/$n2in2 5it/

ti#e= to2et/e" 5it/ c"$c ti! c/e#ic$l "e$ctionso" ot/e" en i"on#ent-in'%ce' c"$c ti! e ect;

SCC $il%"e is $ >"ittle $il%"e $t "el$ti el* lo5const$nt tensile st"ess o $n $llo* e3!ose' in $s!eciJc co""osi e en i"on#ent;

Ho5e e" t/e Jn$l "$ct%"e >ec$%se o o e"lo$' o"e#$inin2 lo$'->e$"in2 section is no lon2e" SCC;


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T/"ee con'itions #%st >e !"esentsi#%lt$neo%sl* to !"o'%ce SCC<

- $ c"itic$l en i"on#ent - $ s%sce!ti>le $llo* - so#e co#!onent o tensile

st"ess


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'ensile

stress

"orrosi#een#ironment

Susceptiblematerial

Stresscorrosion

crac ing

'ensile stressis below yieldpoint

"orrosi#een#ironment isoften specific tothe alloy system

ure metals are moreresistance to S"" but notimmune and susceptibilityincreases with strength


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T*!ic$l #ic"o c"$c s o"#e' '%"in2SCC o sensiti7e' AISI +:. SS

Surface morphology


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E3$#!le o c"$c !"o!$2$tion '%"in2

t"$ns2"$n%l$" st"ess co""osion c"$c in2 (TGSCC)>"$ss


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*xample of cracpropagation duringintergranular stresscorrosion crac ing(+ S"") AS'M A-./carbon steel


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0racture surface oftransgranular S"" onaustenitic stainless steel inhot chloride solution

0racture surface ofintergranular S"" oncarbon steel in hot nitricsolution


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0racture surface dueto intergranular S""

0racture surface due tolocal stress has reachedits tensile strength #alueon the remaining section


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Note t/$t non-s%sce!ti>le $llo*-en i"on#entco#>in$tions= 5ill not c"$c t/e $llo* e en i /el' inone o t/e !otenti$l 7ones;

Te#!e"$t%"e $n' sol%tion co#!osition (incl%'in2!H= 'issol e' o3i'i7e"s= $22"essi e ions $n'in/i>ito"s o" !$ssi $to"s) c$n #o'i * t/e $no'ic!ol$"i7$tion >e/$ io" to !e"#it SCC;

S%sce!ti>ilit* to SCC c$nnot >e !"e'icte' solel*"o# t/e $no'ic !ol$"i7$tion c%" e;


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o(els o stress corrosion

crac)ingSli! ste! 'issol%tion #o'elDiscontin%o%s inte"2"$n%l$" c"$c 2"o5t/

C"$c n%cle$tion >* "o5s o co""osion#ic"o-t%nnelsA>so"!tion in'%ce' cle$ $2eS%" $ce #o>ilit* ($to#s #i2"$te o%t ot/e c"$c ti!s)H*'"o2en e#>"ittle#entKHIC


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Cont"ol?!"e ention <

Re'%ce $!!lie' st"ess le elRe#o e "esi'%$l tensile st"ess (inte"n$l

st"ess)Lo5e"in2 o3i'i7in2 $2ent $n'?o" c"itic$ls!ecies "o# t/e en i"on#ent

A'' in/i>ito"9se #o"e "esist$nt $llo*sC$t/o'ic !"otection


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Alteration o *nvironment

T*!ic$l c/$n2es in #e'i%# $"e <Lo5e"in2 te#!e"$t%"e >%t t/e"e $"e c$ses5/e"e inc"e$sin2 T 'ec"e$ses $tt$c ; E;2 /ot=

"es/ o" s$lt 5$te" is "$ise' to >oilin2 T $n'"es%lt in 'ec"e$sin2 O ( sol%>ilit* 5it/ T;

Dec"e$sin2 elocit* e3ce!tion #et$ls &$llo*s t/$t !$ssi $te (e;2 st$inless steel)2ene"$ll* /$ e >ette" "esist$nce to ,o5in2#e'i%#s t/$n st$2n$nt; A oi' e"* /i2/

elocit* >ec$%se o e"osion-co""osion e ects;


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Re#o in2 o3*2en o" o3i'i7e"s e;2 >oile"ee'5$te" 5$s 'e$e"$te' >* !$ssin2 it t/"% $

l$"2e #$ss o sc"$! steel; Mo'e"n !"$ctice $c%%# t"e$t#ent= ine"t 2$s s!$"2in2= o" t/"% t/e

%se o o3*2en sc$ en2e"s; Ho5e e"= not"eco##en'e' o" $cti e-!$ssi e #et$ls o" $llo*s;

T/ese #$te"i$ls "e %i"e o3i'i7e"s to o"#!"otecti e o3i'e Jl#s;

C/$n2in2 concent"$tion /i2/e"concent"$tion o $ci' /$s /i2/e" $#o%nt o $cti es!ecies (H ions); Ho5e e"= o" #$te"i$ls t/$te3/i>it !$ssi it*= e ect is no"#$ll* ne2li2i>le;


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*nvironment actorsa+ecting corrosion (esign

:D%st !$"ticles $n' #$n-#$'e !oll%tion CO=NO= #et/$ne= etc;

Te#!e"$t%"e /i2/ T & /i2/ /%#i'it*$ccele"$tes co""osion;R$in $ll e3cess 5$s/es co""osi e #$te"i$ls$n' 'e>"is >%t sc$"ce #$* le$ e 5$te"

'"o!lets;P"o3i#it* to se$Ai" !oll%tion N$Cl= SO = s%l %"o%s $ci'= etc;H%#i'it* c$%se con'ens$tion;


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!esign !o,s - !on,ts

W$ll t/ic ness $llo5$nce to $cco##o'$te o"co""osion e ect;A oi' e3cessi e #ec/$nic$l st"esses $n' st"essconcent"$tions in co#!onents e3!ose' to co""osi e#e'i%#s; Es! 5/en %sin2 #$te"i$ls s%sce!ti>le to SCC;A oi' 2$l $nic cont$ct ? elect"ic$l cont$ct >et5een'issi#il$" #et$ls to !"e ent 2$l $nic co""osion;A oi' s/$"! >en's in !i!in2 s*ste#s 5/en /i2/

elocities $n'?o" soli' in s%s!ension $"e in ol e' e"osion co""osion;A oi' c"e ices e;2 5el' "$t/e" t/$n "i et t$n s $n'ot/e" cont$ine"s= !"o!e" t"i##in2 o 2$s et= etc;


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A oi' s/$"! co"ne"s !$int ten's to >e t/inne" $t

s/$"! co"ne"s $n' o ten st$"ts to $il;P"o i'e o" e$s* '"$in$2e (es! t$n s) $ oi'"e#$inin2 li %i's collect $t >otto#; E;2 steel is"esist$nt $2$inst concent"$te' s%l %"ic $ci'; %t i"e#$inin2 li %i' is e3!ose' to $i"= $ci' ten' to $>so">#oist%"e= "es%ltin2 in 'il%tion $n' "$!i' $tt$c occ%"s;A oi' /ot s!ots '%"in2 /e$t t"$ns e" o!e"$tions loc$li7e' /e$tin2 $n' /i2/ co""osion "$tes; Hot s!ots$lso ten' to !"o'%ce st"esses SCC $il%"es;

Desi2n to e3cl%'e $i" e3ce!t o" $cti e-!$ssi e#et$ls $n' $llo*s co7 t/e* "e %i"e O o" !"otecti eJl#s;Most 2ene"$l "%le < AVOID HETEROGENEIT


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&rotective Coatings .

/rappingP"o i'e >$""ie" >et5een #et$l $n' en i"on#ent;Co$tin2s #$* $ct $s s$c"iJci$l $no'e o" "ele$ses%>st$nce t/$t in/i>it co""osi e $tt$c on s%>st"$te;Met$l co$tin2s <

No>le sil e"= co!!e"= nic el= C"= Sn= P> on steel;S/o%l' >e "ee o !o"es?'iscontin%it* co7 c"e$tess#$ll $no'e-l$"2e c$t/o'e le$'in2 to "$!i' $tt$c$t t/e '$#$2e' $"e$s;

S$c"iJci$l n= Al= C' on steel; E3!ose' s%>st"$te5ill >e c$t/o'ic & 5ill >e !"otecte';A!!lic$tion /ot 'i!!in2= ,$#e s!"$*in2=cl$''in2= elect"o!l$tin2= $!o" 'e!osition= etc;


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S%" $ce #o'iJc$tion to st"%ct%"e o" co#!osition >*%se o 'i"ecte' ene"2* o" !$"ticle >e$#s; E;2 ioni#!l$nt$tion $n' l$se" !"ocessin2;Ino"2$nic co$tin2 < ce#ent co$tin2s= 2l$ss co$tin2s=ce"$#ic co$tin2s= c/e#ic$l con e"sion co$tin2s;C/e#ic$l con e"sion $no'i7in2= !/os!/$ti7in2= o3i'eco$tin2= c/"o#$te;O"2$nic co$tin2 < !$ints= l$c %e"s= $"nis/es; Co$tin2

li %i' 2ene"$ll* consists o sol ent= "esin $n' !i2#ent; T/e "esin !"o i'es c/e#ic$l $n' co""osion "esist$nce=$n' !i2#ents #$* $lso /$ e co""osion in/i>ition

%nctions;

corrosion prevention 316.ppt

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