1、 Standard Practice Sacrificial 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 respec
2、t 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 standard is to be construed as granting any right, by implication or othe
3、rwise, 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 interpreted as a res
4、triction 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 assumes no responsibility for the interpretation or use of this s
5、tandard by other parties and accepts responsibility for only those official NACE interpretations issued by NACE in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual volunteers. Users of this NACE standard are responsible for reviewing
6、appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE standard may not necessarily address all potential health and safety problems or environmental hazards associated with the use of mater
7、ials, equipment, and/or operations detailed or referred to within this standard. Users of this NACE standard are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve comp
8、liance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE standards are subject to periodic review, and may be revised or withdrawn at any time in accordance with NACE technical committee procedures. NACE requires that action be taken to r
9、eaffirm, revise, or withdraw this standard no later than five years from the date of initial publication and subsequently from the date of each reaffirmation or revision. The user is cautioned to obtain the latest edition. Purchasers of NACE standards may receive current information on all standards
10、 and other NACE publications by contacting the NACE FirstService Department, 15835 Park Ten Place, Houston, TX 77084-5145 (telephone +1 281-228-6200). Approved 2016-03-31 NACE International 15835 Park Ten Place Houston, Texas 77084-5145 +1 281-228-6200 ISBN 1-57590-331-8 2016, NACE InternationalNACE
11、 SP0216-2016 Item No. 21403 SP0216-2016 NACE International i _ Foreword This NACE International standard practice presents guidelines for sacrificial (galvanic) cathodic protection (SACP) of reinforcing steel in atmospherically exposed concrete elements or structures. These guidelines target owners,
12、 engineers, architects and contractors, and those concerned with mitigation of reinforced concrete corrosion through the application of SACP systems. The information in this standard, as it relates to SACP systems, is intended for atmospherically exposed concrete structures and is not applicable to
13、concrete with nonferrous reinforcement, epoxy-coated, galvanized, or other types of coated reinforcement. SACP has been successfully applied to buried and submerged reinforced concrete structures; however, these applications are not addressed in this standard. TG 047 is comprised of corrosion consul
14、tants, consulting architects and engineers, material manufacturers and suppliers, cathodic protection engineers, metallurgical engineers, researchers, structure owners, contractors, and representatives from both industry and government. For more information on the various SACP systems that are comme
15、rcially available, refer to NACE Publication 01105.1 This standard was prepared in 2016 by Task Group (TG) 047 “Reinforced Concrete: Sacrificial Cathodic Protection of Reinforced Concrete Elements.” TG 047 is administered by Specific Technology Group (STG) 01, “Reinforced Concrete; “and is sponsored
16、 by STG 05, “Cathodic/Anodic Protection.” This standard is issued by NACE under the auspices of STG 01. 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. The terms shall and must are used to sta
17、te a requirement, and are considered mandatory. The term should is used to state something good and is recommended, but is not considered mandatory. The term may is used to state something considered optional. _ SP0216-2016 ii NACE International _ NACE International Standard Practice Sacrificial Cat
18、hodic Protection of Reinforcing Steel in Atmospherically Exposed Concrete Structures Contents 1. General 1 2. Design of Sacrificial Cathodic Protection Systems 2 3. Criteria . 4 4. Installation 7 5. Operation and Maintenance of Sacrificial Cathodic Protection Systems 8 6. Records 10 References 11 Ap
19、pendix A: Glossary of Terms (Nonmandatory) 12 Appendix B: Additional Information Useful for Design (Nonmandatory) 13 Appendix C: Survey Equipment (Nonmandatory) 14 Appendix D: Test Equipment (Nonmandatory) 15 Figure Figure 1: Typical Polarization Decay Curve 5 Figure 2: Typical Polarization Developm
20、ent Curve Showing “Instant Off” Potential Only 6 _ SP0216-2016 NACE International 1 _ Section 1: General 1.1 Background 1.1.1 The corrosion reaction between a metal and its environment is an electrochemical cell. An electrochemical cell consists of four components: an anode, where oxidation occurs;
21、a cathode, where reduction occurs; a metallic path, where current flows; and an electrolyte (concrete), where ion transfer occur in a shared environment. If any one of the four elements of the electrochemical cell is eliminated, corrosion cannot occur. The anodic and cathodic areas can occur, for ex
22、ample, as a result of exposure to differential environmental conditions or coupling dissimilar metals. 1.1.2 Reinforcing steel is compatible with concrete because of their similar coefficients of thermal expansion and because concrete generally provides the steel with corrosion protection. Corrosion
23、 protection is the result of the highly alkaline portland cement that allows a stable, passivating film to form on the surface of the reinforcing steel. This film naturally protects the steel until the film is affected. Mechanisms that affect the protective film and lead to corrosion include carbona
24、tion and other mechanisms that reduce the pH of the concrete and contamination of the concrete by chlorides, and other halides and chemicals that are corrosive to reinforcing steels. Carbonation results from atmospheric carbon dioxide diffusing through concrete and decreasing the alkalinity of concr
25、ete. Chloride contamination also affects the passive film. Chlorides can be cast in concrete or penetrate concrete from external sources such as seawater, deicing salts, or other chemicals. 1.2 Sacrificial Cathodic Protection (SACP) 1.2.1 The basic principles of corrosion can be used to understand t
26、he theory of SACP. SACP is defined as a technique to mitigate corrosion of a metal by making it the cathode in a corrosion cell via the introduction of a metal that is more electrochemically active in that environment than the metal to be protected. 1.3 Scope and Limitations 1.3.1 The provisions of
27、this standard shall be applied under the direction of a registered professional engineer, or a person certified by NACE as a corrosion specialist or cathodic protection specialist. The professionals qualifications should include suitable experience in cathodic protection of reinforced concrete struc
28、tures. Under certain circumstances, a cathodic protection system may either become a structural component or significantly affect the serviceability and structural performance of a reinforced concrete structure; therefore, review of such impact should be made by a structural engineer. 1.3.2 The guid
29、elines presented here are limited to SACP on existing atmospherically exposed concrete structures. This standard applies to both conventionally reinforced concrete and prestressed reinforced concrete. 1.3.3 SACP systems require monitoring provisions to determine the performance and to comply with th
30、is standard. SACP systems used without monitoring systems or methods to measure their performance do not comply with this standard practice as their performance cannot be verified. 1.3.4 Cathodic protection is a proven technique for controlling corrosion of steel in existing structures for certain a
31、pplications. However, cathodic protection neither replaces lost steel nor returns corroded reinforcement to its original diameter. Although a reinforced concrete element may appear sound by traditional inspection techniques after a SACP system is installed, it could be experiencing corrosion-related
32、 tensile stress near ruptures in localized areas. This may lead to movements, deflection, cracking, delaminations or spalls that can appear several years subsequent to the installation of the SACP system. SP0216-2016 2 NACE International 1.3.5 Sacrificial anode systems have inherent limited current
33、output characteristics and electrochemical characteristics. Accordingly, sacrificial cathodic protection systems may not always be the best system for all combinations of structure, environment, distress, and design life. NOTE: For further information, refer to the glossary of terms in Appendix A (n
34、onmandatory). _ Section 2: Design of Sacrificial Cathodic Protection Systems 2.1 Introduction 2.1.1 This section provides guidelines for designing SACP systems for their intended service life. 2.2 Anode selection 2.2.1 SACP systems consist of sacrificial anodes and a connection between the anode and
35、 the reinforcing steel. 2.2.2 The following types of sacrificial anodes are currently available: 2.2.2.1 Embedded discrete anodes 2.2.2.2 Surface-applied anodes 2.2.2.3 Surface-mounted anodes Refer to NACE Publication 011051 for system type and descriptions. 2.3 The design current density range to a
36、chieve cathodic protection is normally between 2 and 11 mA/m2 (0.2 and 1 mA per ft2) of steel. This current density range should be used to determine the required anode mass unless data is available to justify an alternative value. 2.4 Information useful for selecting and designing SACP system inclu
37、des: 2.4.1 As-built drawings of the concrete structure 2.4.2 Condition survey (in accordance with NACE SP03082 and ACI(1) 201.1R-08.3 2.4.3 Corrosion potential survey in accordance with NACE SP0308 and ASTM(2) C8764 2.4.4 Chloride analysis of the concrete 2.4.5 Electrical continuity of the embedded
38、metal 2.4.6 Repair and maintenance history (in accordance with NACE SP03905) 2.4.7 Concrete cover (in accordance with NACE SP0308) (1) American Concrete Institute (ACI), P.O. Box 9094, Farmington Hills, MI 48333-9094. (2) ASTM International (ASTM), 100 Barr Harbor Drive, West Conshohocken, PA 19428-
39、2959. SP0216-2016 NACE International 3 2.4.8 Concrete resistivity data (in accordance with NACE SP0308) 2.5 Parameters for selection of the SACP system 2.5.1 The SACP system shall provide sufficient current to the structure to be protected and distribute this current so that the criterion selected f
40、or cathodic protection is achieved. 2.5.2 The design life of the cathodic protection system must be considered in relation to the remaining service life of the protected concrete structure. 2.5.3 Electrochemical performance of the anodes 2.5.3.1 Anode materials have different rates of consumption wh
41、en discharging a given current density from the anode surface in a specific environment. Therefore, for a given current density, the anode life depends on the electrochemical properties of the anode material as well as physical properties of the anode such as volume, surface area, and geometry. 2.5.
42、3.2 Concrete drying effects can limit the delivery of adequate current levels. A humectant may be used for certain types of anode to enhance the delivery of current under these circumstances. 2.5.3.3 Chemically enhanced mortars have been developed to encapsulate certain types of anode. The mortars a
43、re intended to enhance current delivery. 2.5.4 Structural Considerations 2.5.4.1 Access, maintenance of the right-of-way, ease of repair, and skid resistance (for traffic surfaces) should be considered during the selection of anode systems. Overhead clearance and dead load constraints may preclude t
44、he use of overlay systems for some structural elements. 2.5.4.2 Future repairs to the concrete structure and future extensions to the cathodic protection system should be considered. 2.5.4.3 The physical properties of the selected anode material must be compatible with the concrete structure. 2.5.4.
45、4 The effect of construction and repair techniques that use high-resistivity materials (e.g., epoxy injection), high temperatures (e.g., asphaltic overlays), or impact loads should be considered during the selection of anode systems, instrument design, and wiring methods. 2.6 In the design of SACP s
46、ystems, the following items should be considered: 2.6.1 Detailed specifications should be given for all materials and installation practices and shall include transportation, storage, handling, and disposal requirements for all materials that are to be incorporated in the installation of the SACP sy
47、stem. When performance specifications or requirements are used, specific evaluation procedures should be cited, and recognized industry standards should be listed. Terminology should be clearly defined. 2.6.2 Suitable design drawings that delineate the overall layout of the concrete to be protected
48、should be prepared. The location of significant items of system hardware including but not limited to test stations, electrical bonds, electrical insulators, and adjacent metallic embedments should be shown. 2.6.3 The design should optimize anode layout and installation to achieve the criteria set forth in Section 3. SP0216-2016 4 NACE International 2.6.4 The proximity of anodes to metallic embedments such as form ties, chairs, tie wire, embedment plates, and electrical conduit shall be determined. Minimum depth of cover over the r
