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Cathodic

Protection

Cathodic protection is a corrosion preventiontechnology that deters corrosion from coated metallicstructures (cathode), buried in moist soil (electrolyte)and redirects it to an expendable material (anode).

With a cathodic protection system, a voltage potentialforce (greater than the coated structure's voltagepotential force) is impressed upon the surface of thecoated metallic structure from the anodes. This preventscurrent discharge into the soil by transferring thecorrosion reaction to the anodes.

Electrical isolation is the key to success in cathodicprotection systems. Buried coated metallic structures,protected by cathodic protection systems, must beelectrically isolated. This prevents the protective currentfrom flowing to other buried structures, such as:1. adjacent piping, 2. pipe and equipment within abuilding, 3. pipe passing through steel reinforcedconcrete and 4. any foreign metallic structure in the area.

Electrically Isolated Flange DetailInsulating Material

Our Perma-Pipe Inspection Services department providescathodic protection services that include soil testing,computer generated design/engineering, field installationinstruction, system checkout analysis and the availability ofcathodic protection materials.

Rectifier Systems convert A.C. current to D.C. currentand impress a voltage potential force upon the exteriorsurface of the protected structure through inert anodes(usually carbon or high silicon cast iron). This systemdiffers from the sacrificial anode system only in themanner that current is generated.

(Sacrificial AnodePerma-Pipe's engineers are certified by the NationalAssociation of Corrosion Engineers (NACE) and are expertsin the design of cathodic protection systems. We design,manufacture and service quality piping systems worldwide.

Types of

Cathodic Protection,.,.

Rectifier

= Power

Cost Effective

Cathodic Protection Systems

There are two types of cathodic protection systems -sacrificial anode and rectifiers. In a properly designedand maintained system, both are effective in deterringcorrosion from the exterior surface of buried metallicstructures.

Sacrificial Anode Systems impress a voltage potentialforce onto the outside surface of the protected structureby use of dissimilar metals. The four basic componentsof the systems are:

1. Anodes -Negative electrode in the corrosion cell(usually magnesium or zinc).

2. Cathode -Positive electrode in the corrosion cell(the coated structure, usually iron or steel).

3. Electrolyte -Electrically conductive commonbackfill material (moist soil or water).

4. Connecting Wire -Return path for the corrosioncurrents that are generated between the anode andthe cathode.

Sacrificial anodes are normally installed one of twoways:

1. Each anode wire is welded directly to the protectedstructure or 2. anodes are spliced to a commongathering wire that is laid parallel to the protectedstructure, terminating at the test station where it isconnected to the protected structure by a lead wire. Thismethod provides easy access for measuring thesystem's overall effectiveness.

Direct Connection Type

The use of properly designed, properly maintainedcathodic protection systems can extend the life of buried,coated metallic structures 15 years or longer. The cost ofcorrosion control is minimal when compared to theexpense of maintaining or replacing a deteriorated systemand the disruption or service. Normally, the cost is only 5to 10% of the total installed price of a buried pipedistribution system.Cathodic Protection Systems:

Test Stations.Extend the Life of Buried Metallic Structures.Increase Return on Investment.Reduce Repair Costs.Meet Requirements of DOT and EPA for Hazardous

Materials Containment Vessels and Piping

Common Wire Type

Typical Applications Typical UsersBuried Piping Systems Military BasesBuried Storage Tanks Government InstallationsWalkthrough Tunnels Colleges/UniversitiesSteel Manholes Public Utilities

HospitalsPrivate Industrial Plants

CA THODIC PROTECTION SPECIFICA TION GUIDE

wall sleeves and link seals. It shall bethe responsibility of the contractor to in-stall the underground piping to preventshorting of the system to building steel,reinforcing steel in buildings, manholewalls, foundations and other buried me-tallic structures. Electrical isolationflanges or dielectric unions shall be in-stalled on all piping at all building entriesand wherever else required to electricallyisolate the piping system. Electrical iso-lation materials must be suitable for thetemperatures and pressures of the pip-

ing system.

TEST STATIONS

Test stations shall be located at maxi-mum 300 foot intervals for the purposeof testing the performance of the ca-thodic protection system. Test leadsshall be housed in electrical conduit andterminate in waterproof junction boxes.

GENERAL

Cathodic protection against galvaniccorrosion shall be provided for the un-derground piping furnished under thesespecifications. The cathodic protectionsystem shall be designed and furnishedby the piping system manufacturer. Ca-thodic protection materials, includinganodes, wire and test stations shall besupplied by the cathodic protection sys-tem supplier. Testing of the system asoutlined in the NACE RecommendedPractice RP-O1-69 (Latest Revision)shall be made under the direction of aNACE Accredited Corrosion Specialist.The cathodic protection system shall betested within six months of completionof backfilling.

The cathodic protection system shall bedesigned for a minimum anode life oftwenty years, upon an earth resistivitytest performed by the manufacturer. Asoil survey shall be conducted along theroute of the proposed piping system todetermine the corrosivity of the soil. Thefirm conducting the survey shall be regu-larly engaged in corrosion related workand shall be under the direction of a Cor-rosion Specialist accredited by the Na-tional Association of Corrosion Engi-neers.

INSTALLATION

The installing contractor shall handle the

materials in accordance with the direc-

tions furnished by the cathodic protec-

tion supplier and as approved by the

engineer.

TESTING

After complete backfill of the site by the

installing contractor, the cathodic protec-

tion system shall be tested to provide

conformance to NACE criteria. Criteria

for determining the adequacy of protec-

tion shall be per NACE Standards.

Aluminum 5.3 -6.7%

Manganese 0.15% Minimum

Zinc 2"5 -3.5%

Silicon 0.3% Maximum

Copper 0.05% Maximum

Nickel 0.003% Maximum

Iron 0.003% Maximum

Other 0.3% Maximum

Magnesium Remainder

All anodes shall be cast with a perforatedgalvanized steel strap core. The anodelead wire shall be #12 type THWN solidcopper wire. The anode lead wire shallbe connected to the strap core with sil-ver solder. The anode shall be pack-aged in a permeable cloth bag contain-ing backfill of the following composition:

Hydrated Gypsum 75%

Powdered Bentonite 20%

Sodium Sulfate 5%

Provide granular backfill with 100 per-cent passing through a 100 meshscreen. Provide prepackaged anode ina bag containing the anode and backfill.Center the anode in the firmly packagedbackfill. Anodes should be buried innatural earth.

ELECTRICAL ISOLATION

Piping must be electrically isolated frominternal building piping at the point of con-nection inside the building and at man-hole entries. Dielectric flanges must beinstalled on each pipe and the pipe mustbe isolated from the building wall with

MATERIALS

ANODES-17# Magnesium anodes shall

be used having the following chemical

compositions:

PERMA-PIPE, INC.

A Subsidiary of MFRI, Inc.

7720 North Lehigh Avenue

Niles, Illinois 60714-3491

Phone (847) 966-2235

Fax (847) 470-1204

http:/ /www.permapipe.com

The information contained in this document is subject to change without notice. PERMA-PIPE, Inc. believes theinformation contained herein to be reliable, but makes no representations as to its accuracy or completeness

PERMA-PIPE; Inc. sole and exclusive warranty is as stated in the Standard Terms and Conditions of Sales forthese products. In no event will PERMA-PIPE be liable for any direct, incidental, or consequential damages.@2000 Perma-Pipe, Inc All Rights Reserved Form No. CATH (10/00 6M CG)