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1、 Standard Practice Impressed Current Cathodic Protection of Reinforcing Steel in Atmospherically Exposed Concrete Structures This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any
2、respect preclude anyone, whether he or she has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE International standard is to be construed as granting any right, by
3、 implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents minimum requirements and should in no way be
4、interpreted as a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE International assumes no responsibility for t
5、he interpretation or use of this standard by other parties and accepts responsibility for only those official NACE International interpretations issued by NACE International in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual voluntee
6、rs. Users of this NACE International standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE International standard may not necessarily address all pote
7、ntial health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard.Users of this NACE International standard are also responsible for establishing appropriate health, safety, and environmental prot
8、ection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revised or
9、withdrawn at any time in accordance with NACE technical committee procedures. NACE International requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication. The user is cautioned to obtain the latest edition. Purchasers
10、of NACE International standards may receive current information on all standards and other NACE International publications by contacting the NACE International FirstService Department, 1440 South Creek Drive, Houston, Texas 77084-4906 (telephone +1 281 228-6200). Reaffirmed 2007-03-12 Revised 2000-0
11、6-16 Approved April 1990 NACE International 1440 South Creek Drive Houston, Texas 77084-4906 +1 281/228-6200 ISBN 1-57590-103-X 2007, NACE International NACE SP0290-2007 (formerly RP0290-2000) Item No. 21043 Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employees/1
12、111111001, User=Wing, Bernie Not for Resale, 05/07/2007 21:33:55 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 05/07/2007 21:33:55 MDTN
13、o reproduction or networking permitted without license from IHS -,-,- SP0290-2007 NACE International i _ Foreword The purpose of this NACE standard practice is to present guidelines for impressed current cathodic protection of reinforcing steel in atmospherically exposed concrete structures. This st
14、andard is aimed at owners, engineers, architects, contractors, and all those concerned with rehabilitation of corrosion-damaged reinforced concrete structures. For more information on design, maintenance, and rehabilitation of reinforcing steel in concrete, refer to NACE Standard RP01871 and NACE St
15、andard RP0390.2 For a state-of-the-art overview regarding the use of reference electrodes for atmospherically exposed reinforced concrete structures, refer to NACE International Publication 11100.3 For a state-of-the art overview on criteria for cathodic protection of prestressed concrete structures
16、, refer to NACE International Publication 01102.4 This standard was originally prepared in 1990 by NACE Task Group T-3K-2, a component of Unit Committee T-3K on Corrosion and Other Deterioration Phenomena Associated with Concrete. It was revised by Work Group T-11-1a in 2000, and reaffirmed by Speci
17、fic Technology Group (STG) 01 in 2007. It is issued by NACE International under the auspices of STG 01 on Reinforced Concrete. In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragrap
18、h 7.4.1.9. Shall and must are used to state mandatory requirements. The term should is used to state something good and is recommended but is not mandatory. The term may is used to state something considered optional. _ Copyright NACE International Provided by IHS under license with NACELicensee=IHS
19、 Employees/1111111001, User=Wing, Bernie Not for Resale, 05/07/2007 21:33:55 MDTNo reproduction or networking permitted without license from IHS -,-,- SP0290-2007 ii NACE International _ NACE International Standard Practice Impressed Current Cathodic Protection of Reinforcing Steel in Atmosphericall
20、y Exposed Concrete Structures Contents 1.General 1 2.Definitions 1 3.Criteria . 2 4.Design of Impressed Current Cathodic Protection Systems. 5 5.Installation Practices 7 6.Energizing and System Adjustment. 7 7.Operation and Maintenance of Impressed Current Cathodic Protection Systems 8 8.Records 9 R
21、eferences 10 Bibliography 10 Appendix AAdditional Information Useful for Design (Nonmandatory 11 Appendix BTest Equipment (Nonmandtory) . 12 Figure 1Typical Polarization Decay Curve 4 Figure 2Typical Polarization Development Curve Showing “Instant-Off” Potentials Only 4 _ Copyright NACE Internationa
22、l Provided by IHS under license with NACELicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 05/07/2007 21:33:55 MDTNo reproduction or networking permitted without license from IHS -,-,- SP0290-2007 NACE International 1 _ Section 1: General 1.1 Background 1.1.1 Reinforcing steel is
23、compatible with concrete because of similar coefficients of thermal expansion and because concrete normally provides the steel with excellent corrosion protection. The corrosion protection is the result of the highly alkaline Portland cement that allows a stable, corrosion-mitigating passive oxide f
24、ilm to form and be maintained on the surface of the encased steel. If the film does not form, or is weakened or destroyed so that it does not protect the steel, corrosion can occur. The protective oxide film does not form or is destroyed if (1) excessive amounts of chloride or other aggressive ions
25、are present, (2) alkalinity is lost by reaction with aggressive gases, or (3) the concrete does not fully encase the steel. 1.1.2 Corrosion occurs as a result of the formation of an electrochemical cell. An electrochemical cell consists of four components: an anode, where oxidation occurs; a cathode
26、, where reduction occurs; a metallic path, where the electric current is electron flow; and an electrolyte (concrete), where the electric current is ion flow in an aqueous medium. The anodic and cathodic areas occur as a result of coupling dissimilar metals or exposure to differential environmental
27、conditions. If any one of the four elements of the electrochemical cell is eliminated, corrosion can be prevented. 1.2 Cathodic Protection 1.2.1 The basic principles of corrosion can be used to understand the theory of cathodic protection. Cathodic protection is defined as a technique to reduce the
28、corrosion of a metal surface by making that surface the cathode of an electrochemical cell. 1.2.2 Cathodic protection is a proven technique for controlling corrosion of steel in existing chloride- contaminated concrete structures. However, cathodic protection will neither replace lost steel nor retu
29、rn corroded reinforcement to its original cross-sectional area and strength. There may be areas of the reinforced concrete structure that appear sound by traditional inspection techniques that are, in fact, corroding and experiencing corrosion-related tensile stress near the rupture levels. Such dis
30、tressed areas may crack, spall, or delaminate subsequent to the application of cathodic protection. 1.3 Scope and Limitations 1.3.1 The provisions of this standard should be applied under the direction of a registered Professional Engineer or a person certified by NACE International as a Corrosion S
31、pecialist or certified as a Cathodic Protection Specialist. The persons professional experience should include suitable experience in cathodic protection of reinforced concrete structures. Under certain circumstances, a cathodic protection system may either become a structural component or significa
32、ntly affect the serviceability and structural performance of a reinforced concrete structure; therefore, review of such impact by the cathodic protection system should be made by a qualified registered Structural Engineer or the equivalent. 1.3.2 The guidelines presented here are limited to impresse
33、d current cathodic protection systems for new or existing atmospherically exposed reinforced concrete and are not applicable to prestressed concrete. _ Section 2: Definitions Attenuation: Electrical losses in a conductor caused by current flow in the conductor. Cathodic Protection: A technique to re
34、duce the corrosion of a metal surface by making that surface the cathode of an electrochemical cell. Corrosion Potential (E corr): The potential of a corroding surface in an electrolyte relative to a reference electrode under open-circuit conditions (also known as rest potential, open-circuit potent
35、ial, or freely corroding potential). Depolarization: The removal of factors resisting the current in an electrochemical cell. Design Specifications: A set of documents that, in aggregate, form the nucleus for well-founded, understandable, and equitable contract documents. These documents include wri
36、tten specifications and drawings. Drying Effect: Migration of water molecules away from the anode as a result of current flow. Electrical Continuity: A closed circuit (unbroken electrical path) between metal components under consideration. Electrical Isolation: The condition of being electrically se
37、parated from other metallic structures or the environment. Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 05/07/2007 21:33:55 MDTNo reproduction or networking permitted without license from IHS -,-,- SP0290-200
38、7 2 NACE International Electrode Potential: The potential of an electrode in an electrolyte as measured against a reference electrode. (The electrode potential does not include any resistance losses in potential in either the electrolyte or the external circuit. It represents the reversible work to
39、move a unit of charge from the electrode surface through the electrolyte to the reference electrode.) Energizing: The process of initially applying power to turn on an impressed current cathodic protection system. Foreign Structure: Any metallic structure that is not intended as a part of a system u
40、nder cathodic protection. Immediate Voltage Shift: The difference between the potential value when the power source is on and the instant- off value. (This is also referred to as IR Drop.) Instant-Off Potential: The polarized half-cell potential of an electrode taken immediately after the cathodic p
41、rotection current is stopped, which closely approximates the potential IR drop (i.e., the polarized potential) when the current was on. IR Drop: The voltage across a resistance in accordance with Ohms Law. Overlay: A layer of concrete, mortar, or asphalt placed over and usually bonded onto the worn
42、or cracked surface of a concrete slab to restore or improve the function of the previous surface. Open-Circuit Potential: The potential of an electrode measured with respect to a reference electrode or another electrode in the absence of current. Polarization: The change from the open-circuit potent
43、ial as a result of current across the electrode/electrolyte interface. Polarization Decay: The decrease in electrode potential with time resulting from the interruption of applied current. Potential Survey: Obtaining potentials with respect to a reference electrode at multiple locations on the surfa
44、ce of the concrete structure. Prestressed Concrete: Concrete in which internal stresses of such magnitude and distribution are introduced that the tensile stresses resulting from the service loads are counteracted to a desired degree; in reinforced concrete, the prestress is commonly introduced by t
45、ensioning the tendons. Rectifier: An electrical device for converting alternating current (AC) to direct current (DC). Reference Electrode: An electrode whose open-circuit potential is constant under similar conditions of measurement, which is used for measuring the relative potentials of other elec
46、trodes. Rest Potential: See Corrosion Potential. Step-and-Touch Potentials: The electrical potential gradients that may exist between two points on the electrolyte surface equal to one pace (one meter) or between a grounded metallic object and a point on the electrolyte surface separated by the dist
47、ance equal to a humans normal reach (one meter). Stray Current: Current through paths other than the intended circuit. _ Section 3: Criteria 3.1 The criteria in this section serve as a guide for achieving cathodic protection and providing corrosion control for reinforcing steel embedded in atmospherically exposed concrete. Compliance with these criteria is dependent on analysis of representative data in each situation. These crit