1....sacrificial anodes cp
DESCRIPTION
cathodic protectionTRANSCRIPT
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14-17 March, 2011
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Corrosion Control Techniques5.Cathodic Protection
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Corrosion Control Techniques5.Cathodic Protection
Types of CP Systems
According to the source of external supply of electrons, there are two types of CP systems:
1- Sacrificial anode system
2 - Impressed current system
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Corrosion Control Techniques5.Cathodic Protection
Magnesium
Zinc
Aluminum
Iron
Lead
Tin
Nickel (Active)
Brass
Copper
Nickel (Passive)
410 Stainless
Titanium
304 Stainless
Silver
Gold
Platinum
ACTIVE
NOBLE
1- Sacrificial anode system
Zn
Fe
e- Sim
plified
Galvan
icS
eries
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Corrosion Control Techniques5.Cathodic Protection
Galvanic Couples in Saline Water
Fe/Al Fe Fe/Cu Fe/Ag Cu/Ag
Without electrolyte With electrolyte
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Corrosion Control Techniques 5.Cathodic Protection
Arrangement of a Sacrificial CP System
Anode e- FeDrain Point
I
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Corrosion Control Techniques 5.Cathodic Protection
Common Sacrificial Anodes
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Corrosion Control Techniques 5.Cathodic Protection
Common Sacrificial Anodes
At temp. > 600 C : Al & Zn oxidize leading to Reverse Polarity
AnodeRecommended Electrolyte
Magnesium (Mg)Soils & hot water
Zinc (Zn)Soils & fresh / sea water
Aluminum (Al)Sea waters
Indium is added to aluminum to avoid its oxidation
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Corrosion Control Techniques 5.Cathodic Protection
Generalization :
Aqueous media with low resistivity, Al anode are preferred, e.g. seawater
Mg anodes are used in higher resistivity aqueous media, e.g. wetted soils.
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Prepackaged Sacrificial Anode
Corrosion Control Techniques 5.Cathodic Protection
For soil applications: prepackaged Mg & Zn anodes
Backfill: 75% Gypsum + 20% Bentonite clay + 5% Sodium sulfate
Role of Backfill: to absorb and maintain the soil water, so keeping the anode in wet environment
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Corrosion Control Techniques 5.Cathodic Protection
Main types and shapes of Al & Zn anodes:
1. Slender ( stand-off )
2. Flush mounted
3. Half-shell bracelet
4. Spherical
5. Ribbon
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Corrosion Control Techniques5.Cathodic Protection
Ribbon Anodes ( Zinc / Magnesium ) 55
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Corrosion Control Techniques5.Cathodic Protection
Applications of sacrificial cathodic protection system:
Buried / sub sea pipelines Buried piping Platforms and rigs Maine piles Tank internals
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Corrosion Control Techniques 5.Cathodic Protection
Sacrificial anodes for onshore piping
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Corrosion Control Techniques 5.Cathodic Protection
Typical CP of a buried pipeline with prepackaged sacrificial anodes
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Corrosion Control Techniques5.Cathodic Protection
Sacrificial anodes for platform jackets
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Corrosion Control Techniques5.Cathodic Protection
Sacrificial anodes for platform jackets
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Corrosion Control Techniques
5.Cathodic Protection
Subsea pipeline laying
Bracelet anode FLUSH with cement coating
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Corrosion Control Techniques5.Cathodic Protection
Sacrificial Anode Cathodic Protection for External Side
of Tank Bottom
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Corrosion Control Techniques5.Cathodic Protection
Sacrificial anodes for vessel internals
Sacrificial Anode
Mist Eliminator
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Corrosion Control Techniques5.Cathodic Protection
Corrosive Formation Water
Crude Oil
Vapor
Air in as Tank Breathes
Sever Corrosion Due to Condensed Aerated Moisture
Protective Coatings
Coatings + CP Sacrificial Anodes
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Corrosion Control Techniques5.Cathodic Protection
Sacrificial anodes for tank internals
Painted Anode Side Facing Tank’s Shell
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Corrosion Control Techniques5.Cathodic Protection
Anodes Distribution on Tank Shell
EL +500
EL +7500
EL +5500
EL +3500
EL +1500
SEC A-A
SEC B-B
SEC A-A
SEC B-B
SEC A-A
LL Level
HH Level
SEC A-A
SEC B-B
NN
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Corrosion Control Techniques5.Cathodic Protection
Sacrificial Anodes Layout on Internal Tank Bottom
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Corrosion Control Techniques5.Cathodic Protection
Full filt weld
Tack weld
Sacrificial anodes for tank internals
Anode Fixation on Tank Shell
Anode Fixation on Tank Bottom
U-Bolt
BracketTank FloorAnode Alloy
Steel BarAnode Insert
Anode Fixation on Tank Bottom by Welding
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Corrosion Control Techniques5.Cathodic Protection
Sacrificial Anodes for Ship Hulls
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Thank You and Good Luck