oe ORROSION & ANTICORROSIVES DEFINITION: Undesired degradation of materials by reaction with surrounding media through chemical or electrochemical reaction... 4 CORROSION & ANTICORR
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CORROSION
&
ANTICORROSIVES
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oe
ORROSION & ANTICORROSIVES
DEFINITION:
Undesired degradation of materials by reaction
with surrounding media through chemical or
electrochemical reaction.
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rey
CORROSION & ANTICORROSIVES
STEEL + AIR + WATER ™ RUST
2Fe + O2 + 2H2O >> Fe(OR)2
HEMPRL —
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a
2Fe++ + 4OH- -> 2Fe(OH)2 2Fe(OH)2 + H2O + 1⁄2O2- -> 2Fe(OH)3
HEMPRL —
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CORROSION & ANTICORROSIVES
Air (O2)
` `
- - 2ĐDD€G
Galvanic corrosion
2Fe++ + 4OH- -> 2Fe(OH)2 2Fe(OH)2 + H2O + 1⁄2O2- -> 2Fe(OH)3
HEMPRL —
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4 CORROSION & ANTICORROSIVES
GALVANIC SERIES IN SEAWATER
Noble Graphite
Gold
Titanium
Stainless steel (passive) Bronze
Copper Millscale Brass Stainless steel (active) lron (Steel)
Aluminium Zinc
Magnesium
lgnoble
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“" CORROSION & ANTICORROSIVES
Air (O2)
Corrosion in an acidic environment
lie
N
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CORROSION & ANTICORROSIVES
© G2
0 5 10 15 20 25
Concentration of sodium chloride, weight%
30
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eh oN +
SEER Fe+
+
⁄2O2 + H2O ->
2OH-
wy ow ad wr
SBE Ấ „
=> Zn+
+
1⁄2O2 + H2O ->
2OH-
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CORROSION & ANTICORROSIVES
Barrier effect
| i Inhibitor effect
|
Galvanic effect
HEMIPEL _
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CORROSION & ANTICORROSIVES
BARRIER EFFECT
Leafing pigments Film thickness
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CORROSION & ANTICORROSIVES
ZINC RICH PRIMERS