Formerly the National Association of Corrosion Engineers, NACE International represents members from 92 countries and is the largest organization in the world dedicated to the study of corrosion. NACE works to protect people, infrastructure, the environment, and the economy from the effects of corrosion by promoting engineering and research. Approximately 100 standards cover subjects such as laboratory corrosion testing, corrosion prevention and blast cleaning.
Introduction Reinforced concrete is a versatile and widely used construction material. Its excellent performance and durability rely on the compatibility of the steel with the concrete surrounding it and the ability of the concrete to protect the steel from corrosion in most circumstances. Unfortunately, corrosion protection is not guaranteed, and can fail if sufficient chlorides (usually in the form of sea salt, deicing salt, or chloride contamination of the original mix) or atmospheric carbon dioxide (CO2) penetrate the concrete and break down the passive layer that protects the steel. This breakdown of the passive oxide layer leads to corrosion of the reinforcing steel if sufficient oxygen and water are available. Regardless of the cause of depassivation (chlorides or carbonation), corrosion occurs by the movement of electrical charge from an anode (a positively charged area of steel where steel is dissolving) to the cathode (a negatively charged area of steel where a charge-balancing reaction occurs, turning oxygen and water into hydroxyl ions). This means that the process is both electrical and chemical, i.e., electrochemical. In the case of chloride attack, patch repairs are only a local solution to corrosion, and repairing an anode can accelerate corrosion in adjoining areas. One solution to this problem involves applying an electrochemical treatment that suppresses corrosion. Figure 1 shows the basic components of an electrochemical treatment system. The components are a direct-current (DC) power source and an anode (temporary or permanent) usually distributed across the surface of the concrete. Electrochemical methods work by applying an external anode and passing current from it to the reinforcing steel so that all of the steel becomes a cathode. Three electrochemical techniques are used to counter corrosion of steel in concrete. The first of these techniques is cathodic protection. A newer alternative for chloride-contaminated structures is electrochemical chloride extraction (ECE), also known as electrochemical chloride removal (ECR), or desalination, as the process is called in Europe. A method for treating carbonated concrete has been developed and is gaining rapid acceptance as a rehabilitation method for carbonation in buildings and other structures. This is known as realkalization. Chloride removal was the subject of two major studies conducted under Federal Highway Administration(1) (FHWA) contracts in the 1970s.1,2 Both of these studies, as well as follow-up reports, concluded that chloride removed by electrochemical migration is a promising technique for use on salt-contaminated concrete. Further research was undertaken in Norway by a private company, and under the Strategic Highway Research Program(2) (SHRP). As a result of that research a number of patents were published. A list of some of the principal U.S. patents directly relating to ECE is given in the bibliography. The list is not comprehensive and does not include patents from other countries. The chloride ion acts as though it is a catalyst to corrosion, and is not consumed in the corrosion reaction. Chlorides enable corrosion to develop and expand once they are present beyond a threshold level at the steel surface. Because chlorides are negatively charged, the electrochemical process can be used to repel the chloride ion from the steel surface and move it toward an external anode. The ECE process uses an external anode that is installed for the duration of the treatment process. A higher electrical current density is applied than that used for cathodic protection (see NACE Standard RP02903 on cathodic protection and NACE Standard TM02944 for testing embeddable anodes for cathodic protection of atmospherically exposed steel-reinforced concrete). Normally, the ECE system runs for a limited time (typically four to eight weeks), and is then dismantled and removed from the structure. No permanent system is installed. (!) Federal Highway Administration (FHWA), 400 7th St. SW, Washington, DC 20590. (2) Strategic Highway Research Program (SHRP), National Research Council, National Academy of Sciences, Box 289, Washington, DC 20055.
Introduction Reinforced concrete is a versatile and widely used construction material. Its excellent performance and durability rely on the compatibility of the steel with the concrete surrounding it and the ability of the concrete to protect the steel from corrosion in most circumstances. Corrosion of the steel reinforcement does not occur, despite the presence of moisture and oxygen in the concrete pores, because of the alkalinity of the concrete pore water creating a passive oxide film on the reinforcing steel. Unfortunately, corrosion protection is not guaranteed and can fail if sufficient chlorides (usually in the form of sea salt, deicing salt, or chloride contamination of the original mix) or atmospheric carbon dioxide (CO2) penetrate the concrete. This leads to the breakdown of the passive layer that protects the steel. This breakdown of the passive oxide layer leads to corrosion of the reinforcing steel if sufficient oxygen and water are available. Regardless of the cause of depassivation (chlorides or carbonation), corrosion occurs by the movement of electrical charge from an anode (a positively charged area of steel where steel is dissolving) to the cathode (a negatively charged area of steel where a charge-balancing reaction occurs, turning oxygen and water into hydroxyl ions). One solution to carbonation-induced reinforcement corrosion involves applying an electrochemical treatment that suppresses corrosion. Figure 1 shows the basic components of an electrochemical treatment system for realkalyzing concrete. The components are a direct-current (DC) power source and a temporary anode distributed across the surface of the concrete encased in a conductive medium or electrolyte. Electrochemical methods work by applying an external anode and passing current from it to the reinforcing steel so that all of the steel becomes a cathode. Three electrochemical techniques are used to counter corrosion of steel in concrete. Cathodic protection can be applied by impressed current or galvanic anodes. Electrochemical chloride extraction (ECE) uses a temporary anode and high current over a period of 4 to 6 weeks (see NACE Publication 011011). Realkalization is a method for treating carbonated concrete. It is similar to ECE but takes approximately one week and is gaining rapid acceptance as a rehabilitation method for carbonation in buildings and other structures. Both ECE and realkalization use currents up to about 1 A/m2 (0.1 A/ft2) of steel surface area.
Introduction Over the past several decades the corrosion of steel reinforcement embedded in concrete structures has received considerable worldwide attention. In theory, concrete and reinforcing steel are very compatible. They have similar coefficients of thermal expansion. Concrete, because of its highly alkaline nature, creates a protective environment for the steel. Studies have shown that corrosion activity and damage result when critical quantities of aggressive ions penetrate through the concrete pore structure by diffusion and other transport phenomena and reach the embedded steel reinforcement. At this time, the naturally occurring passive film developed by highly alkaline concrete becomes saturated with these ions, eventually breaking down this protective layer. In regions of low resistance, aggressive ions, mostly in the form of salts, attack the passive film and develop localized anodic sites (pits) on the surface of the steel. Immediately adjacent to these anodic sites are oxygen-rich regions that cathodically "fuel" the corrosion reaction. As active corrosion proceeds, the lower pH in and around the anodic sites reduces the passive layer in greater proportions, making it more prone to iron oxide (Fe2O3) development. Because Fe2O3 (rust) is much more voluminous than solid steel, it imparts considerable tensile forces within the concrete matrix and eventually leads to cracking of the concrete cover. There are several approaches that have been used to rehabilitate concrete structures suffering from the effects of corrosion damage. The most widely used approach typically involves removing the damaged concrete in and around the affected area and replacing it to the original dimension. The principal intent of this remove-and-replace approach is to return the form and function of the structure. Although this strategy is widely used, it rarely incorporates the complete removal of contaminated areas that surround the damaged region, and is sometimes regarded as only a short-term solution. Modifications to this technique include expanding the area excavated to include sound but chloride-contaminated or carbonated concrete, or to include areas where the steel-reinforcement potential is more negative than a defined threshold. The remove-and-replace approach is normally broken into two general categories. The first is patch repair, and the second is rehabilitation. Patch repair is a short-term solution that makes no attempt to extend the structure life, but merely restores concrete back to dimension. The rehabilitation technique attempts to return the distressed area to uniformity with the pre-existing conditions and normalizes any conditions of further distress. The rehabilitation technique carries with it some expectation of an increase in service life. In some applications, a corrosion inhibitor is included either as an additive to the repair/replacement concrete mix or as a post treatment. These methods of concrete repair are much more involved than discussed in this report and are well integrated into most structure owner agencies and the civil engineering community. Alternatively, CP applies electrochemistry to halt the corrosion process or reduce it to levels below engineering significance. Cathodic protection is an electrochemical technique used to reduce the corrosion of metallic materials. This is accomplished through the addition of a cathodic current to the metal-electrolyte system so as to increase the rate of the cathodic reaction (the formation of hydrogen [H2] or hydroxide [OH-]) on the metal being protected, and at the same time decrease the rate of the anodic reaction (metal dissolution). The source of this cathodic current is immaterial to the protection process, and can come from direct current (DC), alternating current (AC), or galvanic sources
FOREWORD This technical committee report reviews the corrosion of reinforcing and prestressing steel in concrete structures caused by stray currents. It provides information on the history of stray-current corrosion, the sources of stray currents, the mechanism of corrosion, the effects on structures, and detection and mitigation of stray-currentinduced corrosion on steel in concrete. Also covered are measures taken during the design phase and modelling of the stray-current effects. The report is intended for use by designers of reinforced concrete (RC) structures, professionals dealing with electrochemical techniques (e.g., cathodic protection [CP], realkalization, and electrochemical chloride removal), owners of structures with the potential for reinforcement corrosion caused by stray currents, owners of systems that could generate stray currents to concrete structures, and electrical engineers. Even though much of the information is applicable to metallic structures, this report focuses only on reinforced and prestressed concrete structures.
Introduction Two practical methods of treatment are available to prevent steel frame corrosion: (a) Treating the steel and changing the environment (e.g., removing the facade, applying protective coatings to the steel, and preventing moisture ingress to the facade); or (b) Controlling the corrosion process electrochemically (e.g., with CP). The former is the current standard method of treatment; however, the widespread stripping of a facade is often impractical and prohibitively expensive because of the necessity of removing large sections of masonry to allow access to the steel frame. The removal of masonry is also of particular concern when heritage buildings are involved. In such applications, a conservation strategy for the facade adds considerable value. The principal electrochemical process for controlling corrosion is CP. CP offers many benefits over traditional repairs, including substantial cost savings, minimal disruption to the building occupants, and conservation benefits that are of particular importance in heritage buildings. The CP of steel-framed buildings is possible because the protective current can be passed through the stonework or masonry to the steel through the mortar/masonry contact. However, although the steel and masonry layout details often exist, it is not always easy to determine the connection between the two elements.
Foreword This technical committee report describes current industry practices and gives information on the most commonly used generic coating systems for protection of threaded fasteners used with structural steel, piping, and equipment. The coating system provides a protective barrier between the base metal and the environment to minimize the effect of corrosion. The information presented in this report addresses steel quality, pretreatment processes, coating application, quality assurance/quality control, and test comparisons for evaluating corrosion resistance. This report does not reflect the NACE position on these practices, but rather summarizes existing technology and practices of various manufacturers, applicators, and users. This technical committee report was prepared for the use of engineers, purchasing agents, coating inspectors, and project leaders in any industry having corrosion problems with threaded fasteners. The purpose is to provide information on the various generic coating systems currently available for corrosion protection of threaded fasteners. This technical committee report was prepared by NACE Task Group 148 on Coatings and Methods of Protection for Threaded Fasteners Used with Structural Steel, Piping, and Equipment. It is issued by NACE under the auspices of Specific Technology Group (STG) 02 on Coatings and Linings, Protective: Atmospheric.
Introduction Field investigations by Romanoff and other researchers at the National Institute of Standards and Technology (NIST)(formerly the National Bureau of Standards [NBS])(1) in the 1960s and earlier demonstrated that steel pilings are not significantly affected by corrosion in undisturbed soil, regardless of the soil type and properties.1 On the other hand, recent examinations of steel piles exposed during bridge-pier construction in several states have revealed severe corrosion damage, including complete severing of the piles in corrosive soil strata. The problem appears to be associated primarily with the use of man-made materials such as slag and cinders for fill around the piling. Extensive corrosion damage has also been observed in related structures such as reinforced soil structures in similar environments. (1) National Institute of Standards and Technology (NIST) (formerly National Bureau of Standards [NBS]), Gaithersburg, MD 20899.
General Structure-to-soil potential measurements to determine the effectiveness of CP is sometimes prone to error due to unstable reference cell contact or high soil IR drops. In certain soil environments, effective CP is achieved even at potentials less negative than the applicable criteria (on or off potentials, 100-mV polarization, etc.) because of the low corrosiveness of the soil and its chemistry. CP potential coupons are used to assess the adequacy of CP on pipelines through coupon potential measurements. 1,2,3 These measurements include coupon off and depolarization potential measurements used for alternative criteria mentioned in NACE SP0169,4 such as –850-mV off or 100-mV cathodic polarization. CP potential coupons are also used in situations in which it is not possible to interrupt multiple CP sources or on structures with direct connected galvanic anodes. As in the case of pipeline internal corrosion rate measurements, metal weight loss coupons have been used for soil-side applications in the past to determine the effectiveness of CP. More recently, ER corrosion measurement probes,5,6 typically used for internal corrosion monitoring, have been manufactured specifically for use in soil-side applications. ER probes may be a better indicator of CP effectiveness in areas affected by dynamic stray traction current, telluric current-affected pipelines, and also in areas of alternating current (AC) induction and AC-induced corrosion (ACIC). LPR-type probes measure corrosion rates of metals, but only without CP. The fundamental theory of the validity of LPR requires that the measurements be made at the freecorroding potential of the metal. The measurement technique is invalidated as soon as CP current is applied. In addition, because these probes make electrochemical measurements, they typically need a sufficiently conductive medium in which to make the measurements. (1) Photo courtesy of Naeem Khan, Saudi Aramco, Dhahran 31311, Saudi Arabia. (2) Photo courtesy of Schiff Associates, 431 W. Baseline Rd., Claremont, CA 91711. (3) Photo courtesy of Rohrback Cosasco Systems, 11841 E. Smith Ave., Santa Fe Springs, CA 90670. (4) Photo courtesy of Naeem Khan, Saudi Aramco, Dhahran 31311, Saudi Arabia. (5) Drawing courtesy of Rohrback Cosasco Systems, 11841 E. Smith Ave., Santa Fe Springs, CA 90670, and Naeem Khan, Saudi Aramco, Dhahran 31311, Saudi Arabia. (6) Graph courtesy of Rohrback Cosasco Systems, 11841 E. Smith Ave., Santa Fe Springs, CA 90670.
introduction hvdc transmission is used to carry electrical energy over long distances or to interface two alternating current (ac) power systems that might not be synchronized. hvdc transmission can be performed using monopolar systems, which are typically earth-return systems, or bipolar wire-return systems. in monopolar systems, power is transmitted through a metallic conductor in one direction; see figure 1. (ig refers to current flow in the earth). monopolar earth return systems use the earth as a conductor, and they typically use the sea as the earth return because of its low resistance and its ability to conduct large currents for a sustained period of time. continuous operation of monopolar hvdc transmission systems is prohibited in some countries.
Foreword An increasing number of wastewater structures, systems, and components are experiencing extreme corrosion and deterioration. Hydrogen sulfide (H2S) corrosion and microbiologically influenced corrosion (MIC) are principal contributors to the problems. The purpose of the report is to increase awareness of the problem of corrosion, and to provide a high-level overview of the current state-of-the-practice and current state-of-the-art renewal technologies for rehabilitation, repair, and replacement of existing systems, structures, and components in wastewater systems. This report is intended for use by design engineers, decision makers, and other stakeholders in municipalities who are involved with the management, design, construction, maintenance, and/or operation of potable, sewer, and storm water systems, components, and structures.
foreword an increasing number of wastewater structures, systems, and components are experiencing extreme corrosion and deterioration. hydrogen sulfide (h2s) corrosion and microbiologically influenced corrosion (mic) are principal contributors to the problems. the purpose of the report is to increase awareness of the problem of corrosion, and to provide a high-level overview of the current state-of-the-practice and current state-of-the-art renewal technologies for rehabilitation, repair, and replacement of existing systems, structures, and components in wastewater systems. this report is intended for use by design engineers, decision makers, and other stakeholders in municipalities who are involved with the management, design, construction, maintenance, and/or operation of potable, sewer, and storm water systems, components, and structures.
Foreword The purpose of this technical committee report is to review data on corrosion and corrosion protection of ductile and gray cast-iron pipe from literature in the U.S. and abroad (gray-iron pressure pipe is no longer produced in North America). Throughout this report, gray cast iron is referred to as "cast iron." The following subjects are covered in this technical committee report: • Engineering practices with respect to ductile- and cast-iron pipe; • Reported protective measures and results obtained by their use; • Influence of the different properties of the two types of iron pipe; and • Case histories of installations spanning decades in a wide range of soils. This report provides the user, owner, engineer, contractor, and other interested parties with technical and general information as to the state-of-the-art with regard to understanding techniques and methods used to mitigate corrosion of iron pipe and fittings. It includes discussions of both historical and recent practices in which corrosion is a potential problem. This technical committee report is not a standard, and as such, it does not cover compliance with any particular specifications, although specifications and standards are cited as references. There are a variety of opinions concerning the benefits of various corrosion control systems for cast- and ductile-iron pipe, which are discussed in pertinent sections of this report. Each method or technique presents the designer and the user with numerous factors that have an impact on installation and operating costs. It is intended that the reader use the report in its entirety and use the information as well as the cited resources when he or she makes decisions about corrosion control for his or her particular situation, and that he or she finds this report a useful source of information and an engineering tool in making decisions associated with corrosion protection. This report was originally prepared in 1992 by NACE Task Group T-10A-21, a component of Unit Committee T-10A, "Cathodic Protection." It was revised in 2012 by Task Group (TG) 014, "Corrosion Control of Ductile and Cast Iron Pipe." TG 014 is administered by Specific Technology Group (STG) 35, "Pipelines, Tanks, and Well Casings," and is sponsored by STGs 02, "Protective Coatings and Linings—Atmospheric," 03, "Protective Coatings and Linings—Immersion/Buried," 05, "Cathodic/Anodic Protection," and 39, "Process Industry—Materials Applications." This report is published by NACE under the auspices of STG 35.
Foreword The present trend in establishing an effective level of external metallic surface corrosion control is the application of a barrier coating or adhesive on the metallic surface prior to the application of a thermal insulating material. Experience has shown that there is generally a limited beneficial effect from the application of cathodic protection (CP) to a bare or ineffectively coated metallic surface under thermal insulation. This NACE technical committee report was prepared as an information guide for external corrosion control of thermally insulated underground metallic surfaces and considerations of the effectiveness of CP. This report is intended for those dealing with thermally insulated structures or pipelines. Although pipelines are the primary focus of this report, the principles discussed would be applicable when a thermal insulating material has been applied on or in the immediate proximity of an underground metallic surface. This report was originally prepared in 1992 by NACE Task Group (TG) T-10A-19, a component of Unit Committee T-10A on Cathodic Protection and was reaffirmed with editorial changes in 2006 by Specific Technology Group (STG) 35 on Pipelines, Tanks, and Well Casings. It is published by NACE under the auspices of STG 35.
introduction in the interest of public safety, transit system operators have an obligation to cooperate willingly with utility operators in the mitigation of stray current created by transit operations and assist the utility corrosion engineer promptly in mitigating the adverse effects of these stray currents when these effects are properly demonstrated. generally, all parties are represented on local corrosion control coordinating committees (see the sections titled "new transit systems" and "new utility systems") and fully cooperate with each other in sharing information about the operation of their respective systems. transit operators are normally aware of the technical and economic corrosion control requirements of the utilities and other owners and the laws and regulations under which they must operate. likewise, utility operators, accustomed to controlling corrosion from older transit systems with drainage bonds, recognize the advances that have been made in stray current control through the improved design and maintenance of the modern rail system. installation of bonds to modern rail systems negates the benefits of corrosion mitigation measures designed into the rail systems. if a significant stray current problem develops, the utility and transit engineers typically work together to attempt to mitigate the problem. to protect their own and neighboring structures, rail operators have an obligation to maintain the rail system in such a manner that does not compromise the built-in stray current control. in this report, utility operator refers to the owner or operator of any underground utility structure.
Introduction In the recent past the costs of damage due to corrosion of reinforced concrete have risen dramatically. Concrete structures such as bridges, parking garages, buildings, and marine docks exposed to chlorides from either deicing salts or the local environment are subject to deterioration. Chlorides that are introduced into the reinforced concrete structure initiate corrosion by destroying the passive film that is naturally formed on steel in concrete. The corrosion products of steel occupy several times the volume of the steel itself and exert tensile stresses on the surrounding concrete. Cracking of the concrete develops, and, ultimately, spalling of the concrete takes place. This can render the structure unsound for use.
Introduction Monitoring of cooling tower operation falls into two major categories. The first deals with the monitoring and control that is directed at maintaining cooling water chemistry within defined specifications. This includes both the components introduced by the supply of make-up water and those added to control scale, corrosion, and microbiological activity. The second monitoring activity includes measurements that assess the severity of scaling, corrosion, or microbiological processes during a campaign of operation. The data obtained from the second category of measurements are used to refine the specifications that form the basis for the water treatment strategy.
foreword this technical committee report provides a state-of-the-art overview of the corrosion and corrosion protection activities related to residential and small commercial water heaters used in potable water systems. it is beyond the scope of this report to address all corrosion factors for all residential and small commercial water heaters on a global basis. an effort has been made, however, to describe the most prevalent water heaters used today, with accompanying information on operation and maintenance. this report is also intended as a technical and application resource for the broad range of persons involved with the manufacture, distribution, and installation of water heaters. this report is not intended as a guide for improved or altered manufacturing procedures for water heaters. this technical committee report was prepared by task group (tg) 147, "water heaters: internal corrosion in potable water systems," which is administered by specific technology group (stg) 11, "water and water treatment systems." this report is issued by nace under the auspices of stg 11.
Foreword Effective microbiological control is an important aspect of a successful cooling water treatment program. It has often been said that more cooling water treatment programs fail because of poor microbiological control than for any other single reason. Consequences of poor biological control typically include biological fouling, microbially influenced corrosion (MIC), accelerated decay of cooling tower wood, and potential amplification of disease-causing microorganisms such as Legionella pneumophila. Bacteria, fungi, algae, and protozoa are the microorganism classes of concern in cooling water systems. To control the growth of these organisms, programs employing oxidizing microbicides, nonoxidizing microbicides, and biodispersants are often used. This technical committee report discusses specific technologies used to control these classes of microorganisms. This report provides owners, engineers, contractors, and operators with specific information on the types of organisms found in cooling systems, a list of common chemistries used for their control, and methods that are typically employed to monitor systems. Its intent is not to serve as a guide to set up a microbiological control program, but to assist users in understanding the components of in-place programs and discuss the treatment program typically used to avoid misapplication. While this report includes a list of common technologies used to treat biofouling, it is not meant to be exhaustive. This technical committee report was prepared by Task Group (TG) 151 on Biocide Monitoring and Control Techniques. TG 151 is administered by Specific Technology Group (STG) 11 on Water Treatment and sponsored by STG 46 on Building Systems and STG 62 on Corrosion Monitoring and Measurement—Science and Engineering Applications. It is issued by NACE International under the auspices of STG 11.
Introduction Corrosion of stainless steel, carbon steel, and aluminum takes place to varying degrees under thermal insulation in the presence of moisture. Water and/or steam may enter the insulation space through penetration points in the jacket, by capillary action (wicking) through or around the insulating medium, or through damaged steam coils. The presence of moisture can lead to general corrosion, pitting, and/or cracking. Because the exterior surfaces of the tank car shell and the interior surfaces of the jacket are not normally inspected after the original construction, such corrosion may go undetected for a great portion of the tank car's expected life unless the jacket is removed. The potential for significant corrosion under insulation on rail tank cars can be related to: • operating temperature; • constituents in the insulation that form corrosive solutions when combined with moisture; • the tendency of some insulation material to absorb and/or retain moisture; • the insulation's lack of adhesion to the substrate; and • contact with the commodity being transported. Corrosion was first detected under foam insulation applied to tank cars in the 1960s. Some urethane foams were found to have a propensity to release acids upon exposure to heat and moisture. Consequently, all insulation systems used on tank cars are now subject to corrosion testing in accordance with AAR(1)Specification M-1002, Section 188.8.131.52 This corrosion test is actually designed for foam-in-place (FIP) urethane. In addition to corrosion testing for the insulation system, Section 2.2.12 requires that the exterior surfaces of carbon steel tanks and the interior surfaces of carbon steel jackets be given a protective coating. This state-of-the-art report describes types of insulation and coating systems used on tank cars to provide corrosion control. Temperature limitations are provided for each system.