1....sacrificial anodes cp

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Delta consulting Delta consulting 1 1 14-17 March, 2011

description

cathodic protection

Transcript of 1....sacrificial anodes cp

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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

11

22

3344

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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