1、 third editionManual of Water Supply PracticesM27External Corrosion Control for Infrastructure SustainabilityM27-Corrosion.indb 1 9/12/13 3:18 PMPrinted on recycled paperAmerican Water Works Association6666 West Quincy AvenueDenver, CO 80235-3098awwa.orgManual of Water Supply Practices M27, Third Ed
2、itionExternal Corrosion Control for Infrastructure SustainabilityCopyright 2014 American Water Works AssociationAll rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information
3、or retrieval system, except in the form of brief excerpts or quotations for review purposes, without the written permission of the publisher.DisclaimerThe authors, contributors, editors, and publisher do not assume responsibility for the validity of the content or any consequences of its use. In no
4、event will AWWA be liable for direct, indirect, special, incidental, or consequential damages arising out of the use of information presented in this book. In particular, AWWA will not be responsible for any costs, including, but not limited to, those incurred as a result of lost revenue. In no even
5、t shall AWWAs liability exceed the amount paid for the purchase of this book.AWWA Senior Manager of Editorial Development and Production: Gay Porter De NileonAWWA Senior Technical Editor/Project Manager: Martha Ripley GrayCover Art: Cheryl ArmstrongProduction: Janice Benight Design StudioAWWA Senior
6、 Manuals Specialist: Molly BeachLibrary of Congress Cataloging-in-Publication DataExternal corrosion.External corrosion control for infrastructure sustainability. - Third edition.pages cm. - (Manual of water supply practices ; M27)Includes index.ISBN 978-1-58321-966-9 - ISBN 978-1-61300-245-2 1. Cor
7、rosion and anti-corrosives. 2. Water-pipes-Corrosion. I. American Water Works Association. II. Title. TA462.E98 2013628.15-dc232013022195Printed in the United States of AmericaISBN-13 978-1-58321-966-9 eISBN-13 978-1-61300-245-2M27-Corrosion.indb 2 9/12/13 3:18 PMiiiContentsAWWA Manual M27List of Fi
8、gures, vList of Tables, viiPreface, ixAcknowledgments, xiChapter 1 Importance of Controlling External Corrosion . . . . . . . . . . . . . . . . . . . . . . . 1Corrosion: Occurrence and Implications, 2Economics of Corrosion Control, 6References, 6Chapter 2 Chemistry of Corrosion . . . . . . . . . . .
9、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Basic Electrochemistry of Corrosion, 7Chemistry of Corrosion in Water Systems, 14Chapter 3 Evaluating the Potential for Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Field and Laboratory Measurements, 26Stray C
10、urrents, 31MIC (Microbiologically Influenced Corrosion), 33Effects of the Chemical Environment on Common Water Pipe Materials, 34References, 47Chapter 4 Corrosion Control and Protection of Buried Pipelines . . . . . . . . . . . . . . . 49Coatings and Linings, 50Cathodic Protection, 52Materials Selec
11、tion, 60Trench Improvement, 60Protective Methods for Specific Pipe Materials, 60References, 65Chapter 5 Atmospheric Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67How Metals Corrode in the Atmosphere, 68Types of Corrosion That Can Be Expected, 70Metho
12、ds of Control, 73Coating Evaluation, 77Stainless Steel in Aboveground Environments, 77References, 77Chapter 6 Corrosion Control of Water Storage Tanks . . . . . . . . . . . . . . . . . . . . . . . . . 79Corrosion of Water Tanks, 79Corrosion Prevention for Water Tanks, 81Conclusion, 86References, 86G
13、lossary, 87Index, 91List of AWWA Manuals, 97M27-Corrosion.indb 3 9/12/13 3:18 PMThis page intentionally blank.M27-Corrosion.indb 4 9/12/13 3:18 PMvAWWA Manual M27Figures1-1 Metals used in a typical gate valve, 31-2 Metals used at a typical water-service-to-main connection, 41-3 Metals used in a pipe
14、-repair clamp, 42-1 The four basic elements of a galvanic corrosion cell: anode, cathode, electrolyte, and electronic path, 82-2 Chemical reactions in a typical galvanic corrosion cell, 92-3 Galvanic cell formed with nonuniform electrolyte and electrodes of a single metal, 102-4 Creating a galvanic
15、cell with a single piece of metal in a nonuniform electrolyte, 112-5 Contrasting conventional current flow with electron movement in a galvanic corrosion cell. Current flow in the electrolyte is by ion transport, 122-6 A typical electrolytic corrosion cell, 132-7 Direct-current transportation system
16、 as a source of current causing electrolytic corrosion, 152-8 Measuring cell voltage with a voltmeter, 152-9 Concentration cell (crevice) corrosion, 192-10 Pitting corrosion (arrows indicate positive current flow), 192-11 Impingement corrosion, 202-12 Photograph of sulfur joint corrosion failure of
17、gray iron pipe caused by a combination of corrosive characteristics of the sulfur joint material used to pack the joint and MIC, 212-13 Stress, fatigue, and fretting corrosion, 222-14 Selective corrosion, 232-15 Dezincification of a brass valve seat, 242-16 Atmospheric corrosion, 243-1 The four-pin
18、system of soil-resistivity testing, 263-2 Use of a single probe for testing soil resistivity, 273-3 Quad-box for testing resistivity of a water-saturated soil sample, 273-4 Testing soil pH, 283-5 Testing for pipe-to-soil potential, 293-6 Failure caused by stray current, 313-7 Example joint bond: coa
19、t exposed wire, thermite weld, and steel after welding, 323-8a Unrestrained joint per AWWA M11 (AWWA C200-type steel pipe), 373-8b Restrained joint per AWWA M11 (AWWA C200-type steel pipe), 373-9 Reinforced concrete cylinder pipe (AWWA C300-type concrete pipe), 403-10 Prestressed concrete lined cyli
20、nder pipe (AWWA C301-type concrete pipe), 403-11 Prestressed concrete embedded cylinder pipe (AWWA C301-type concrete pipe), 403-12 Bar-wrapped concrete cylinder pipe (AWWA C303-type concrete pipe), 414-1 Cathodic protection system (galvanic cell using sacrificial anodes), 524-2 Details of a sacrifi
21、cial anode installation, 544-3 Details of an impressed-current system, 57M27-Corrosion.indb 5 9/12/13 3:18 PMvi AWWA Manual M274-4 Corrosion caused by electrical discontinuity in a cathodically protected pipeline, 584-5 Corrosion of a metal structure in the vicinity of a cathodically protected struc
22、ture, 594-6 Three methods for polyethylene encasement of ductile-iron pipelines, 645-1 Schematic of the four requirements for atmospheric corrosion, 685-2 The effects of orientation on atmospheric corrosion, 695-3 Crevice corrosion or pack rust, 715-4 Stress-related galvanic corrosion of fasteners,
23、725-5 Application of coating system, 756-1 Typical cathodic protection system for ground storage reservoir, 836-2 Typical cathodic protection system for elevated tank, 84M27-Corrosion.indb 6 9/12/13 3:18 PMAWWA Manual M27 vii2-1 Galvanic series of selected metals and alloys (in seawater), 172-2 Typi
24、cal soil corrosion cells resulting from nonuniform electrolyte conditions, 223-1 Soil-test evaluation for ductile-iron pipe (10-point system), 35 3-2 Soils grouped in order of corrosive action on steel, 383-3 Relationship of soil corrosion to soil resistivity, 383-4 Guidelines for use of AC pipe bas
25、ed on pH of acidic soils, 443-5 Corrosion guidelines for AC pipe for soluble sulfate in water and soils, 443-6 Stainless steel alloys and their corrosion resistance, 453-7 Suitable applications for stainless steels, 464-1 Magnesium anode factors, 555-1 Comparison of uniform corrosion rates of differ
26、ent metals in the atmosphere, 70TablesM27-Corrosion.indb 7 9/12/13 3:18 PMThis page intentionally blank.M27-Corrosion.indb 8 9/12/13 3:18 PMixCorrosion control is a practical science that allows relatively reliable predictions of corrosive conditions and, more importantly, effective prevention or mi
27、tigation strategies to control corrosion where economically appropriate. Faced with how best to install and protect a transmission or distribution system to minimize corrosion, todays water utility manager must compare the cost of implementing reliable corrosion protection with the benefit of ensuri
28、ng an extended life for pipelines and appurtenances.Both the technology and the economics involved in external corrosion control are complex, requiring a logical and well-considered approach by utility managers, operators, and consulting engineers, all of whom must be familiar with local conditions
29、and available options. Not all environments are corrosive, not all materials corrode, and there is no single answer to all corrosion problems. In any given situation, the corrective measure selected must be at once the most appropriate for the material and environment involved and eco-nomically feas
30、ible.This manual is addressed primarily to the professional water utility operator, whose objective is to provide safe drinking water to the public. The title has been revised for the third edition to reflect the basic premise that corrosion control is an attempt to extend the useful life of water i
31、nfrastructure. The text is intended to give the reader an understand-ing of how and why corrosion occurs, how the corrosion potential of an environment is evaluated, and how many of the proven corrosion prevention and control measures oper-ate. For readers who believe a review of theoretical concept
32、s of basic chemistry and basic electrical circuit theory is necessary beyond that which is addressed herein, the relevant sections of Basic Science Concepts and Applications* are recommended.Updates in this third edition were made to the figures, tables, and text, including dis-cussion of the effect
33、s of chemical environment on pipe materials, pitting and crevice corro-sion, common water pipe coatings, and recommended protective methods for specific pipe materials. Topics added or expanded on include stray current corrosion, microbiologically induced corrosion (MIC), oxygen-concentration cells,
34、 crevice corrosion of stainless steel, galvanic corrosion, and stainless steel in aboveground environments. New emphasis was placed on using field and lab measurements to determine corrosive conditions. The general principles and examples presented in this manual are not intended to replace the serv
35、ices of a knowledgeable corrosion engineer. However, methodical appli-cation of the principles introducedi.e., determining the cause of corrosion, analyzing its extent, and considering appropriate procedures for prevention or mitigationwill lay the foundation for an effective corrosion control progr
36、am that will benefit the public and the utility alike.In the selection and application of corrosion monitoring, protection, and mitigation materials, the operator must confirm that materials in contact with the water supply have been tested and certified in accordance with the standards and regulati
37、ons relevant to the water utility involved.*Basic Science Concepts and Applications, 3rd ed., American Water Works Association, Denver, Colo-rado (2010), ISBN 9781583217788.AWWA Manual M27Preface M27-Corrosion.indb 9 9/12/13 3:18 PMThis page intentionally blank.M27-Corrosion.indb 10 9/12/13 3:18 PMA
38、cknowledgmentsThis is the third edition of AWWA Manual M27, retitled External Corrosion Control for Infrastructure Sustainability. Members of the Corrosion Committee involved in its develop-ment and approval included the following:Andrew E. Romer, Chair, AECOM, Orange, Calif.David H. Kroon, Vice-Cha
39、ir, Corrpro/Aegion, Houston, TexasGraham E. C. Bell, Secretary, HDR Schiff, Claremont, Calif.Steven E. Cooper, Uni-Bell PVC Pipe Association, Louisville, Ky.Stuart L. Greenberger, Portland Water Bureau, Portland, Ore.John M. Grocki, Splash Inc., Enfield, Conn.David T. Haines, NACE International, Hou
40、ston, TexasSylvia C. Hall, Ameron International Corporation, South Gate, Calif.L. Gregg Horn, Ductile Iron Pipe Research Association, Hoover, Ala.Mike Horton, US Pipe that is, a corrosion reac-tion involves both chemical reactions and the flow of electrons. Two basic types of corro-sion occur in a w
41、ater system: galvanic corrosion and electrolytic corrosion. This section discusses the basic physical configurations and chemistry of each type.M27-Corrosion.indb 7 9/12/13 3:18 PM8 EXtErnal Corrosion Control for infrastruCturE sustainabilityAWWA Manual M27Galvanic CorrosionThe galvanic corrosion pr
42、ocess is identical to the reactions in an electrical battery, in which electrical current is generated by immersing two dissimilar metals, called electrodes, in a chemical solution (electrolyte) and connecting them with an external conducting wire, referred to as the electronic path. Figure 2-1 show
43、s the elements of a galvanic corrosion cell. Note the solid arrows indicating the direction of electron movement and the black/gray arrows indicating positive current flow. Numerous figures throughout the document illustrate corrosion cells of various types. Most of these show electron flow as “e.”
44、Cur-rent flow through the electrolyte is by ion transport and not electron flow. Free electrons do not exist in the electrolyte.In the galvanic cell, corrosion takes place at the surface of the electrode where elec-trons are generated to travel through the metal path. This electrode is called the an
45、ode.The conducting solution (water, soil, or some other chemical solution) is called the electro-lyte. The electrode to which electrons flow is called the cathode. These four elementsthe anode, cathode, electrolyte, and electronic pathmust exist before corrosion can occur.Anode(IronFe)Electrolyte*(H
46、2O)Electron Flow (e)Positive Current FlowCorrosioneeeeElectronic Path* The charge carrier in the electrolyte is ions, not electrons. Cathode(CopperCu)Figure courtesy of NACE International .Figure 2-1 The four basic elements of a galvanic corrosion cell: anode, cathode, electrolyte, and electronic pa
47、thM27-Corrosion.indb 8 9/12/13 3:18 PMChEmistry of Corrosion 9AWWA Manual M27Chemistry. The basic electrochemical reactions occurring in a galvanic corrosion cell are fairly simple. In the cell shown in Figure 2-2, the iron (Fe) anode on the left is corroding. Some of the iron atoms release electron
48、s, which travel across the electronic path and enter the cathode. This loss of electrons changes the iron atoms from elemental iron (Fe) to fer-rous iron (Fe2+) and then to ferric iron (Fe3+), leaving them with a strong positive charge. Some of the molecules of the electrolyte, in this case pure wat
49、er (H2O), are naturally sepa-rated into hydrogen ions (H+) with positive charges and hydroxyl ions (OH) with negative charges. The positively charged iron atoms are attracted to the negative OHions. The attraction causes the iron atoms to leave the anode and enter the electrolyte, where they combine with OHions. As atoms are lost, the metal surface of the anode deteriorates. This deterioration is corrosion. Note that the products of corrosion, Fe(OH)2and Fe(OH)3 , may accumulate on or near the corroded surface.At the cathode, the negatively c
