PS Magazine - TB 43-PS-454
PS, The Preventative Maintenance Monthly
ISSUE 454
SEPTEMBER 1990
Types
of CORr±SI²N
lL
(³ F1´Mk)
Affects a largE arEa of Expos± mTal
sr
likE Rust on st²l oR ta³ish on
silvEr. GRadually R±ucEs thE thicknEss of
thE MEt´l until It faµls.
OccuRs in cREVicEs cReated by RubBR
SE´ls, ¶askEts· ¸lt heads¹ lap joints¹ dº» oR
othER su¼aC dEposits. Will dEVElop any½
whErE MoistuRE oR otHR coRRosiVE a¶Ent is
tRapPd aNd unablE to drain oR EVa¾¿atE.
SEI
±e²
-.±²³´,
O
ElEMEntÀ usually thE anodic ElEMEnt
of an alloy¹ ÁRrÂEs away¹ leavin¶ thE
cathodic ElEMEntà Äan cREatE holEs in
MeT´l.
³R
ÅEsults whEn a Movin¶ fluid (¶as or
liquid) flows across a ÆEÇal¹ paȵcularly
whEn solid paRticlEs aRE presEnt in thE
fluid. ÄoÉRosion actually occuRs on thE suR-
facE of thE MEtalÊ but thE Æovin¶ fluid
washes aw´y thE coRRosion produc± and
ExposEs a nEw MeÇaL su¼acE¹ which also
coRRodes.
iNr
ËEtal detERioraTµon causEd by coRÌosion
of
t
bonds BÍÎn oR acRoss thE ¶Rain
¸undaRiEs of a MEÇalÏ ËEtal appEaRs to B
peElin¶ oF in shÐtsÊ ÑÒakin¶¹ oR bEµn¶
pushEd apaRt by layERsÃ Ó pa»ÔculaR typE
o
ÕntER¶ranular coRrosÖon is Exfo×iation.
PT
Äan REsult fÌoM conditions siMµlaR to
thosE foR crEvicE coRRosion. Øits can dEÙ
vElop on VaRious MatERials duE to thEiR
coMposition. ÅÚflE boREs aRE bi¶ victiMs of
piÛµn¶.
ÜErM
u
to dEscRibE stREss coRrosion
cRackin¶ and coRRosion fatµ¶uE.
OAYa´
OÝurS whEn Þo dÖffEREnt kinds of MEtß
als arE touchin¶¹ likE sDzl ¸lts on aluMiÙ
nuMÀ for ExaMplE. A coMMon pÌoblEÆ on
aircRaà BcausE oá thEiR Mix of MEÇals.
Fµt
Occurs BtwÐn Çwo piEcEs of wEi¶htâ
BaRµn¶ MEtal in contacÇã usually idEntiÑiEd
by a black powdEr corRosion pRÂucÇ oR
pºts on
t
suäaceå
W
I
TH µliLS
XNOWL£&±,
YoU CAI
anR/cl.²T±
whEP pM51¶em·
¸¹º»¼ ½£¾AD
CRr¿cÀ
ÁÂÃÄ
ÅF YÆU ÇaNÈ ÈÆ dIsÉÊaY ËÌÍs ÎÏNÈÏÐÉIÏÎÏ ÆN YÆUÐ BUÑÑÏÒIN BÆaÐÓÔ ÆÉÏN sËaÉÑÏsÕ ÑIFÖ ÅË Æ×Ë aNd ÉIN IÖ UÉØ
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