Cathodic protection fundamentals

CATHODIC PROTECTION FUNDAMENTALS

CATHODIC PROTECTION DIVISION

PREPARED BY : ABINASH PADHY NDTCCS

HISTORY OF NDTCCS IN CATHODIC PROTECTION

• NDT Corrosion Control Services (NDTCCS) is a fully owned Saudi Company operating since 1975. NDT & CCS is one of the subsidiary company of well known Abdullah Al-Shuwayer group. Recently major share of NDT CCS has been acquired by Investcorp Bank, a leading financial GCC institution as part of strategic partnership between Abdullah Al-Shuwayer group and Investcorp

• NDTCCS offers Cathodic Protection & NDT Services (Conventional & Advanced).

• Our Cathodic Protection solutions can prevent corrosion in new structures and mitigate corrosion in existing structures for pipelines, refineries, above and underground storage tanks for every industrial market including offshore and marine, which includes Feasibility studies, site surveys, system design,intereference control systems, installation supervision, system commissioning and maintenance. We also supply wide range of CP materials such as Transformer rectifiers, ICCP Anodes & SACP anodes, Junction boxes, remote monitoring systems etc.

CATHODIC PROTECTION SERVICES

CATHOSIC PROTECTION PRE-DESIGN SURVEY

CATHODIC PROTECTION DESIGN ENGINEERING

CATHODIC PROTECTION INSTALLATION FOR

ONSHORE & OFFSHORE

CATHODIC PROTECTION SYSTEM MONITORING AND MAINTENANCE

CATHODIC PROTECTION MATERIAL SUPPLY

CATHODIC PROTECTION SURVEYS

WHY CATHODIC PROTECTION

Corrosion costs money.

The only successful and cheapest way of saving deterioration of metals from corrosion.

No coating is 100% perfect so cathodic protection used in conjunction with coatings to prevent metals from corrosion.

DIAGRAMS DEPICTING CORROSION

WHAT IS CATHODIC PROTECTION

• Cathodic protection is a method for reducing the corrosion rate that can be applied to buried and submerged metallic structures

• Making the structure cathode of a macroscopic corrosion cell by impressing current onto the structure from an external electrode called

Anode.

HOW DOES IT WORK?

• Cathodic protection current is impressed from an external cathodic protection anode through the electrolyte to the metal and reduces the potential difference between anodic and cathodic sites.

TYPES OF CATHODIC PROTECTION SYSTEMS

CATHODIC PROTECTION

ICCPSACP

SACRIFICIAL ANODE CATHODIC PROTECTION SYSTEM

Test Station

Structure

Sacrificial Anode

Flow of Current through Electrolyte

IMPRESS CURRENT CATHODIC PROTECTION SYSTEM

CURRENT DISTRIBUTION

TRANSFORMER RECTIFIER

• AC inputVoltage, Single/ three phase,

Frequency

• DC maximum output Amp, Volt

• Air Cooled: with sun-shadeOil Cooled: with thermometer

• Location: according to area classification • Explosion proof (hazardous area)• Non-explosion proof (non-

hazardous area

IMPRESS CURRENT ANODES

COMMON ICCP ANODES

MMO Coating

Solid Titanium Core

Titanium Substrate with a Copper Core

Titanium Tubular

Titanium Substrate Mesh

Titanium Substrate Ribbon

GRAPHITE ANODES

PLATINIZED ANODE

IMPRESS CURRENT ANODES ARE SOMETIMES PACKAGED WITH THE CARBONACEOUS BACKFILL

SACRIFICIAL ANODES

SACP ANODES

MAGENSIUMALUMINIUM

ZINC

ALUMINIUM ANODESZINC ANODE

MAGNESIUM ANODES BACKFILLED MAGNESIUL ANODES

INSTALLATION OF ICCP SYSTEM

DEEP-WELL GB HORIZONTAL SHALLOW GB

DITRIBUTED ANODES

TYPES OF GROUND-BED

Non-metallic vent tube

DEEP WEEL GROUNDBED

One or more anodes installed vertically at a nominal depth of 15 meter (50 ft.) or more below the earth’s surface in a drilled hole for the purpose of supplying cathodic protection for an underground or submerged metallic structure.

CARBON BACKFILL

TO MAINTAIN THE STABILITY OF THE DRILLED HOLE

TO SERVE AS THE PRIMARY ANODIC REACTION SURFACE

TO LOWER THE RESISTANCE TO EARTH OF THE SYSTEM

SHALLOW BED GROUND BED

DEPTH- 3 TO 5 MTR

DISTRIBUTED GROUND BED

ANODE CONNECTION

CABLES FROM ANODE GROUND BED

MAIN CABLE TO +VE TERMINALOF TR

POSITIVE JUNCTION BOX

CP OF ABOVE GROUND NEW TANKS

UNDERTANK WATERING SYSTEM

ICCP Anode Grit

Tank

PVC

Wat

erin

g Pi

pe

To T/R

Compacted Soil

DISTRIBUTED ANODE CP FOR TANKS

CP FOR WELL CASINGS

CP OF TANK INTERNALS

Hanging ICCP anode

ICCP anodePVC Support

CP FOR OFFSHORE JACKETS

CATHODIC PROTECTION CRITERIA

DescriptionPotential vs. Cu/CuSO4

mV

Free Corrosion -700

Zone of Cathodic Protection -900

Intense Corrosion-600

Sever Over-Protection Problems

-1200

Increased Over-Protection -1100

Some Over-Protection -1000

Some Protection -800

CATHODIC PROTECTION MONITORING

Structure to electrolyte Potential measured with a Reference Electrode

For soil – Copper Copper Sulfate

For Sea Water – Silver Silver Chloride

Electrode Placement- i. For Pipelines- on the line @ every 1-2 km ii. For Tanks – Under the tank

CSEPerforated PVC Pipe Filled with Water

Tank

Perforated PVC Pipe Installed for Reference Electrode Placement

AVO

POTENTIAL MEASUREMENT OF OFFSHORE STRUCTURES

Diver with Portable Reference Electrode

POTENTIAL MEASUREMENT OF WELL CASINGS

TP-3TP-1 TP-2

wellTP

TP-3 TP-4

- 850 mV Min. protection levelUn protected

area

Pipe

to so

il pote

ntial

- mV

What about the potential at any point ?

Buried pipeline ( 1.2 meter deep)

Well casing8000 feet deep

The criterion most widely used on pipelines is based on measurementsof potential differences between the pipeline and its environment

.ie: more negative than ( - 850 mv) reference to Cu/Cu So4 cell

MONITORING TEST POSTS

Flush – to – ground

CABLE CONNECTIONS

Prior to welding :The coating must be removed at welding point ( 5x5 cm square ) Metal surface to be polished and cleaned

Pin Brazing Unit

Pistol / Gun

Pins & Ferrules

Lug

Grinder

ELECTRICAL ISOLATION

Structure to be protected should be electrically isolated from the structures which do not require protection

Thank you