1、 Standard Practice Cathodic Protection to Control External Corrosion of Concrete Pressure Pipelines and Mortar-Coated Steel Pipelines for Water or Waste Water Service This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and p
2、rovisions. Its acceptance does not in any 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 standard is to be constru
3、ed as granting any right, by 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 requireme
4、nts and should in no way be 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 assumes no respon
5、sibility for the interpretation or use of this standard 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 t
6、his NACE 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 standard may not necessarily address all potential health and safety problems or enviro
7、nmental hazards associated with the use of materials, 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 regu
8、latory authorities if necessary, to achieve compliance 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 CAUTIONARY NOTICE: NACE standards are subject to periodic review, and may be revised or withdrawn at any time in accordance with NACE technical committee pro
9、cedures. NACE requires that action be taken to reaffirm, 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
10、may receive current information on all standards and other NACE publications by contacting the NACE FirstService Department, 15835 Park Ten Place, Houston, TX 77084-5145 (telephone +1 281-228-6200). Revised 2014-06-26 Revised 2008-11-07 Reaffirmed 2004-09-15 Approved 2000-01-14 NACE International 15
11、835 Park Ten Place Houston, Texas 77084-5145 +1 281-228-6200 ISBN 1-57590-096-3 2014 NACE International NACE SP0100-2014 (formerly RP0100) Item No. 21090 SP0100-2014 NACE International i _ Foreword The purpose of this standard practice is to furnish guidelines that provide corrosion control personne
12、l, owners, operators, designers, manufacturers, and contractors with information on controlling external corrosion of embedded steel in concrete pressure pipelines and mortar-coated steel pipelines for water or waste water service through the application of cathodic protection (CP). The guidelines p
13、resented are applicable to new or existing buried pipelines with or without a supplemental coating. The provisions of this standard should be applied under the direction of competent persons who are qualified to engage in the practice of corrosion control on buried or submerged metallic pipelines. S
14、uch persons may be licensed professional engineers or persons recognized as corrosion specialists or CP specialists by NACE. The professional experience of such persons should include suitable experience in CP of prestressed concrete structures, if protection of that type of structure is being plann
15、ed. This standard was originally prepared in 2000 by NACE Task Group T-10A-28, a component of Unit Committee T-10A on Cathodic Protection. To provide the necessary expertise on all aspects of the subject and in order to receive input from all interested parties, Task Group T-10A-28 was composed of c
16、orrosion consultants, consulting engineers, architect-engineers, CP engineers, researchers, pipeline owners, and representatives from both industry and government. The standard was reaffirmed in 2004 by Specific Technology Group (STG) 05, “Cathodic/Anodic Protection” and revised in 2008 and 2014 by
17、Task Group (TG) 019, “Mortar-Coated Pipes: Cathodic Protection Criteria.” This standard is issued by NACE under the auspices of STG 05. 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 term
18、s shall and must are used to state 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. _ SP0100-2014 ii NACE International _ Cathodic Protection
19、to Control External Corrosion of Concrete Pressure Pipelines and Mortar-Coated Steel Pipelines for Water or Waste Water Service Contents 1. General . 1 2. Definitions . 2 3. Types of Concrete Pressure Pipe and Mortar-Coated Steel Pipe 3 4. Determination of Need for CP 4 5. CP Criteria 5 6. Design of
20、 CP Systems . 6 7. Installation of CP Systems . 13 8. Energizing and System Adjustment . 15 9. Operation and Maintenance of CP Systems . 17 10. CP Records 19 References 21 Bibliography . 22 FIGURES Figure 1: Polarization diagram 1 Figure 2: Typical Polarization Development and Decay Curves 6 Figure
21、3(a): Bonding Cable on Inside . 11 Figure 3(b): Bonding Clip 11 Figure 3(c): Bonding Cable on Outside Using Steel Plate . 11 Figure 3(d): Bonding Cable on Outside Using Modified Anchor Blocks 11 Figure 3(e): Bonding Clip 12 Figure 3(f): Bonding Bar . 12 Figure 3(g): Bonding Cable . 12 Figure 3(h): B
22、onding detail for steel pipe. . 12 _ SP0100-2014 NACE International 1 _ Section 1: General 1.1 Introduction 1.1.1 Concrete and steel are considered compatible materials because they have similar coefficients of thermal expansion and because concrete usually provides steel with excellent corrosion pr
23、otection. Because of the high alkalinity of portland cement, a stable, corrosion-mitigating, passive oxide film forms on the surface of the encased steel. If this film does not form or is weakened or destroyed, corrosion can occur. 1.1.2 The protective oxide film formed on steel encased in concrete
24、does not form or will be destroyed if the concrete does not fully encase the steel, the alkalinity of the concrete is lost by reaction with aggressive gases or liquids, or excessive amounts of chloride or other aggressive ions are present. If one or more of these conditions exists and moisture and o
25、xygen are in contact with the steel, corrosion can occur. 1.1.3 Corrosion occurs because of the formation of an electrochemical cell. An electrochemical cell consists of four components: an anode, at which oxidation occurs; a cathode, at which reduction occurs; a metallic path through which electric
26、al current passes as a flow of electrons; and an electrolyte (concrete pore solution) through which electrical current passes as a flow of ions in an aqueous medium. If any one of the four elements of the electrochemical cell is eliminated, corrosion is prevented. 1.1.4 Within the electrochemical ce
27、ll, the location of relative anodic and cathodic areas can be determined through potential (voltage) measurements. This is accomplished by measuring the potential between a metal immersed or embedded in an electrolyte and a stable reference electrode. This technique may also be used to assess the ef
28、fectiveness of CP. 1.2 Cathodic Protection (CP) 1.2.1 The basic principles of corrosion can be used to understand the theory of CP. CP is defined as a technique to reduce the corrosion of a metal surface by making that surface the cathode of an electrochemical cell (see Figure 1). Figure 1: Polariza
29、tion diagram.1Ea: Equilibrium or “open circuit” potential of anodic area Ec: Equilibrium or “open circuit” potential of cathodic area Ea,p: Polarized potential of anodic area (potential as observed on real structure) Ec,p: Polarized potential of cathodic area (potential as observed on real structure
30、) SP0100-2014 2 NACE International 1.2.2 If corrosion of steel is found in a concrete pressure pipeline or a mortar-coated steel pipeline, CP may be used to control further corrosion. However, CP does not replace lost steel or return corroded steel to its original cross-section. 1.2.3 Electrical con
31、tinuity of the steel elements within the pipe sections and between individual pipe sections is required for adequate CP; see Paragraph 6.8. 1.3 This standard serves as a guideline for establishing minimum requirements for CP of the following: 1.3.1 New pipelines: CP is usually not required on new pi
32、pelines because of the passive film that forms on steel embedded in portland cement concrete or portland cement mortar. Cracks or damage caused by construction activities may be a consideration for application of CP. Environmental conditions described in Paragraph 1.1.2 also warrant consideration of
33、 CP; otherwise, the pipeline should be monitored periodically to determine whether corrosion might be occurring. 1.3.2 Existing pipelines: Studies should be made to determine the extent of active corrosion on the pipeline. If these studies indicate that corrosion is affecting the safe or economic op
34、eration of the pipeline, adequate corrosion control measures, which may include CP, should be taken. 1.3.3 CP should be provided and maintained if investigations indicate that corrosion is or might be occurring and adequate electrical continuity exists or can be established. 1.4 Special conditions s
35、ometimes exist in which CP is ineffective or only partially effective, such as shielding by nearby structures. Deviation from this standard may be warranted in specific situations provided that the corrosion control personnel in charge demonstrate that the objectives expressed in this standard are a
36、chieved. 1.5 For accurate and correct application, this standard must be used in its entirety. Using or citing only specific paragraphs or sections can lead to misinterpretation and misapplication of the recommendations and practices contained in this standard. This standard does not designate pract
37、ices for every specific situation because of the complexity of conditions to which buried or submerged pipelines are exposed. _ Section 2: Definitions Anode: The electrode of an electrochemical cell at which oxidation occurs. (Electrons flow away from the anode in the external circuit. It is usually
38、 the electrode where corrosion occurs and metal ions enter solution.) Attenuation: Electrical losses in a conductor caused by current flow in the conductor. Cathode: The electrode of an electrochemical cell at which reduction is the principal reaction. (Electrons flow toward the cathode in the exter
39、nal circuit.) Cathodic Protection (CP): A technique to reduce the corrosion rate of a metal surface by making that surface the cathode of an electrochemical cell. Continuity Bond: A connection, usually metallic, that provides electrical continuity between structures that can conduct electricity. Ele
40、ctrical Continuity: The condition of being electrically connected to other metallic components or structures. Electrical Isolation: The condition of being electrically separated from other metallic structures or the environment. Electrolyte: A chemical substance containing ions that migrate in an el
41、ectric field. Energizing (Turn On): The process of initially applying power to a CP system. Foreign Structure: Any metallic structure that is not intended as a part of a system under cathodic protection. Galvanic Anode: A metal that provides sacrificial protection to another metal that is more noble
42、 when electrically coupled in an electrolyte. This type of anode is the electron source in one type of cathodic protection. Groundbed: One or more anodes installed below the earths surface for the purpose of supplying cathodic protection current. SP0100-2014 NACE International 3 Hydrogen Embrittleme
43、nt: Embrittlement caused by the presence of hydrogen within a metal or alloy. Impressed Current: An electric current supplied by a device employing a power source that is external to the electrode system. (An example is direct current for cathodic protection.) Instant-Off Potential: The polarized ha
44、lf-cell potential of an electrode taken immediately after the cathodic protection current is stopped, which closely approximates the potential without IR drop (i.e., the polarized potential) when the current was on. Interference: Electrical currents flowing on or off unintended structures. IR Drop:
45、The voltage across a resistance when current is applied in accordance with Ohms Law. Isolation: See Electrical Isolation. Polarization: The change from the corrosion potential as a result of current flow across the electrode/electrolyte interface. Polarization Decay: The change in electrode potentia
46、l with time resulting from the interruption of applied current. Polarized Potential: (1) (general use) the potential across the electrode/electrolyte interface that is the sum of the corrosion potential and the applied polarization. (2) (cathodic protection use) the potential across the structure/el
47、ectrolyte interface that is the sum of the corrosion potential and the cathodic polarization. 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; i
48、n prestressed concrete cylinder pipe (PCCP), the prestress is introduced by tensioning the prestressing wire helically around the concrete core or steel cylinder. Rectifier: An electrical device for converting alternating current (AC) to direct current (DC). Reference Electrode: An electrode having a stable and reproducible potential, which is used in the measurement of other electrode potentials. Reverse-Current Switch: A device that prevents the reversal o
