Cathodic Protection for Life Extension of Existing Reinforced Concrete Bridge Elements (2009)

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34 Problems with cathodic protection system application have been experienced in all aspects of the application process, from selection of the appropriate system through installation to the regular monitoring and maintenance of the systems. Each phase of the application process is discussed in this chapter to ascertain the areas in most need of improvement. SELECTION OF A CATHODIC PROTECTION SYSTEM The results of the survey conducted in this effort indicate that, in general, agencies do perform visual, crack, and delamina- tion surveys during routine bridge inspection, which provides them with information to determine if corrosion has been ini- tiated in their structures and whether it needs attention. Once corrosion-induced damage reaches a certain threshold, which is probably different for each state, a corrosion condition eval- uation is performed that generally includes chloride ion con- tent analysis and half-cell potential testing. Such data would provide a good idea of susceptibility to future corrosion in sound areas. If chloride ion distribution at the steel depth has either exceeded or is close to the threshold and the top layer of the sound concrete has high levels of chloride ion concen- tration, the reinforced concrete element is a good candidate for cathodic protection. However, judging from the response to survey questions, it appears that the quantity of damage is considered by most agencies to be the determining factor. Although the quantity of damage is a good indicator of what is happening, waiting for a certain level of damage to occur increases the total cost of repair. If instead of quantity of damage chloride ion content is used, the structures would be prioritized earlier for installation of a cathodic protection system and would result in lower total cost of repair. Between 55% and 60% of the responding agencies have some form of standards, procedures, protocols, or methodology for conducting corrosion condition evaluations, analyzing the data, and using the data to select alternatives for repair and reha- bilitation. This means that a good number of them either do not need or do not have a standardized procedure for implementing this or other technologies. It is reasonable to expect that the standards, procedures, and protocols used by the agencies vary; whereas some may be in need of an update, others may be the state of the art. Several attempts have been made to develop a protocol or a decision matrix that can be used to identify alter- natives that are likely candidates for the particular project based on corrosion condition survey results. The latest in the series is the Manual developed under an NCHRP study that documents a methodology for conducting corrosion condition evaluations and selecting alternatives based on its results (48). In addition to determining the applicability of cathodic protection for a particular structure, it is also necessary that the corrosion condition data provide information on whether galvanic or impressed current cathodic protection will be required. The results of the survey indicate a trend toward the use of galvanic cathodic protection systems. Galvanic cathodic protection systems have a current delivery limit that is controlled by the type of anode and the environment and may not provide sufficient current in certain applications. At the start of the industry, in the 1970s, the E Log I test was used to determine the current requirement. Owing to equip- ment and time requirements, this test is rarely used today. Experienced practitioners use all or some combination of chloride ion distribution, severity of the environmental expo- sure, half-cell potential survey results, corrosion rate measure- ments, electrical conductivity measurements, and quantity of damage information to ascertain if galvanic or impressed cur- rent systems will be required. Therefore, it is imperative that agencies either use in-house personnel with appropriate skill sets or hire a consultant with the requisite qualifications and experience to make the selection decision. DESIGN OF SYSTEM Proper design of a cathodic protection system is paramount. Good design guidelines and criteria will ensure that system designs meet some minimum standard. The available guide- lines and criteria for cathodic protection on reinforced con- crete structures are not sufficient. At present the following two documents are available: 1. NACE SP0290-2007 Standard Practice for “Impressed Current Cathodic Protection of Reinforcing Steel in Atmospherically Exposed Concrete Structures,” devel- oped by the National Association of Corrosion Engi- neers, published in 2007. 2. Guide Specification for Cathodic Protection of Concrete Bridge Decks, developed by a joint committee of AASHTO, AGC, and ARTBA, and was published 1994. CHAPTER FIVE PROBLEMS ENCOUNTERED WITH CATHODIC PROTECTION SYSTEM APPLICATION

35 The NACE standard is the more recent document and pro- vides broad guidelines as to what might be considered during design and relies on professional experienced personnel to make the decisions. The AASHTO document does go into design detail for each type of system; however, many of the newer systems are not included and some of the included sys- tems are no longer used. Neither of the documents provides a basic template for project specifications that might be used as a basis by designers. Only six agencies from among those that responded to the survey have a standard for design and/ or construction specifications governing the use of cathodic protection on reinforced concrete bridge elements. Another document that is presently being developed by NACE is a Recommended Practice for Sacrificial Cathodic Protection of Reinforcing Steel in Atmospherically Exposed Concrete Structures. The Europeans in 2000 have recently published the standard EN 12696:2000 for implementation of cathodic protection technology. The state of Missouri identified the need for a new guide specification and suggested that if one could be provided that the DOTs could ratify the use of NACE standards and recommended practices. Once a decision has been made as to which type of cathodic protection system is to be used, the anode material and con- figuration needs to be selected. Based on the results of the survey, it is clear that for a majority of the agencies, agency staff designs these systems. Some agencies are assisted by a consultant, although fewer require a consultant to design the system with assistance from either a NACE-certified Cathodic Protection Specialist or the material manufacturer or supplier. Even for agencies that have a well-established and experienced staff to handle cathodic protection issues, good information on all materials and configurations may not be available and when a need arises for a material or config- uration other than what they have previously used, they must rely on information from material manufacturers and suppli- ers. Information from material manufacturers and suppliers can be valuable; however, the agency must have the exper- tise to evaluate that information. FDOT stated that “many agencies are reluctant to accept the technology because there have been too many overzealous sales representatives and they do not have in-house expertise to evaluate the proposed systems.” Texas reported that they do not have the requisite skill sets and “all we really know is what the sales people tell us.” A consultant stated that designers allow “material or other commercial considerations to push design.” That would only be possible if the designer is not an independent party and has commercial interests in the materials or supplies for cathodic protection systems. Some earlier specifications required that the designer not have any vested interest in the manufacture or supply of cathodic protection materials. When the first applications of cathodic protection started, FHWA and local DOTs were performing research and exper- imenting with various anode materials and configurations. As funding for such research dried up, users depended more on information provided by the material suppliers and manufac- turers, which may not always be considered from an indepen- dent source. For many of the newer materials, very little infor- mation from independent sources is available. A well-defined test method or guidelines for evaluating anode materials and their various configurations is required. The evaluation of the anode materials and configurations might be done by the agen- cies themselves or by independent research and testing groups. At present, the primary indicator of success used by many sales groups is the number of applications of the particular material and its acceptance by other agencies. Often, there are no hard data or sufficient length of operation to ascertain the performance and the long-term durability of the material. Therefore, this method of acceptance of an anode material based on sales figures can be flawed. Not only might the per- formance and durability of the anode material be considered but its applicability to the subject project could be evaluated. In an interview, the Manager of DP-34 Cathodic Protection for Reinforced Concrete Bridge Decks stated that after FHWA involvement in the cathodic protection industry was reduced in 1989, many agencies had not yet acquired sufficient expertise in the technology and became dependent on vendors and mate- rial suppliers for all aspects of the use of the technology. He stated that “It was a free for all and many materials which were not ready for use were pushed into the marketplace.” He also indicated that the lack of competition in the industry is a prob- lem. He presented the example of the ferex anode. As soon as the material was identified as having good properties to serve as an anode material, the sales and marketing teams pushed the material on numerous bridge structures (at least 50) without verifying the performance or the durability of the material in concrete. Almost of all of these systems failed. Missouri reported them failing between 0 to 5 years, California reported that they failed between 6 to 10 years, and in South Dakota the systems failed immediately after installation. A consultant involved in the use of this system believes that the ferex anode failed because it becomes brittle in concrete, subsequently cracks and the inner copper core becomes exposed. The cop- per core is not a satisfactory anode material and it corrodes rapidly at the application of current and the anode quickly fails. Missouri concurred with this observation and stated that this anode material was not suited for use in concrete. The manager of DP-34 believes that some of the newer anode materials making their way into the marketplace may have similar problems. Even when well-established anode materials and configu- rations are selected, the design parameters need to be properly established. The present design protocols only require the design to limit the voltage drop along the anode material; they do not provide any mechanism for or require the calculation or estimation of other system parameters. Mathematical mod- els are currently available for such calculations and estima- tions (49). The design of the cathodic protection system on the Benjamin Franklin Bridge in Philadelphia did not properly estimate the system requirements. The overall resistance of the system came out to be too high and the rectifiers specified

for the project cannot provide the required current. To reduce the resistance of the circuit and keep the system partially oper- ating, the owner has to regularly spray water on the underside of the approach slabs to reduce system resistance. Design could also include the impact of other systems present on the structure. For example, the cathodic protection system on the bridge carrying I-64 in Norfolk, Virginia, can- not be operated owing to supposed interference between the rectifiers and other electrical systems on the bridge. This sys- tem was installed to protect approximately 400,000 square feet of the deck surface area. Upon energization of the sys- tem, it was observed that the rectifier cards were failing with- in weeks. When operational, the system was providing ade- quate protection. The cause of the burnout of the rectifier cards was not confirmed; however, several theories were put forth by the involved parties including short circuits, ground- ing problems, interference from alternating current on the bridge for lighting, etc. (34). A review of the impact of the cathodic protection system into the bridge electrical grid was never conducted. In another example, an impressed current cathodic protection system on a bridge deck or decks in New Jersey failed to provide corrosion control because the design- ers had not included the impact of corrugated metallic forms present at the bottom of the bridge deck(s). Owing to its large surface area, a majority of the cathodic protection current was received by the corrugated forms and an insufficient amount was received by the reinforcement. The failure of the zinc foil with adhesive anodes on the hammer heads of the James River Bridge and the Route 58 eastbound lane over Leatherwood Creek (both in Virginia), was attributed to the orientation of the panels of zinc in the vertical direction, which allowed water to flow along the joints and enter the space between the anode and the adhesive resulting in dis- bondment (34). Placement of rectifiers on bridge decks where they are susceptible to lightning strikes required the Virginia DOT to keep replacing several control cards every year on the James River Bridge when the conductive paint system was installed on the hammerheads. The rectifiers had alternating current and direct current lightning arrestors; however, these arrestors were destroyed after the first lightning strike and the control cards were damaged during subsequent strikes. The project manager for DP-84 indicated that in several projects in which DP-84 was involved, rectifiers suffered damage from light- ning strikes. Thus, design could also include a careful selec- tion of the placement of the rectifiers and protection against lightning and vandalism. In addition to good design, a detailed set of specifications is required for installation. The specifications would take into account the actual condition of the structure. In one project in Florida, the zinc expanded mesh system in a jacket failed to provide adequate cathodic protection. Analysis of the failure indicated that the project specifications did not provide any instructions to remove the existing jacket and the new jacket 36 had been installed on top of the existing jacket and therefore the cathodic protection system was unable to function. INSTALLATION AND QUALITY CONTROL Proper installation is necessary for the success of any system. Therefore, qualified individuals must be used to install cathodic protection systems. If qualified installers are not available, then the installers might be required to obtain assistance from qualified consultants who can provide guidance and quality control. A qualified quality control and quality assurance provider must be included in the installation process. There are several examples of systems that are nonoperational from the time of installation. On the underside of the roadway of the Brooklyn Battery Tunnel, a mixed metal oxide mesh anode was installed and encapsulated with shotcrete. Improper installation resulted in the shotcrete disbonding from the underside of the roadway at many locations. The problems were not identified during installation. This multimillion dollar system had to be dis- carded as it was not fully functional (50). A similar problem was encountered on the Queen Isabella Causeway in Texas; however, owing to good quality control, the encapsulation was properly installed after three attempts and the system func- tioned as expected. Similarly, during installation of a mixed metal oxide mesh system on the top and the bottom surface of the historic arches of the Jefferson Street Memorial Bridge in Fairmont, West Virginia, a trained and experienced inspector was able to detect the slight variation in the color of the anode, which implied that the mixed metal oxide had not been sin- tered to the titanium expanded mesh. The supplier denied it at first and had the contractor install the defective material. Test- ing of the suspect mesh verified the lack of mixed metal oxide on the mesh and it cost the contractor $500,000 to correct the problem. The last reported inspection, after 5 years of opera- tion, indicated that the system is functioning as designed. Electrical shorts between the anode and the reinforcing steel are the most common problems encountered in the instal- lation of these systems. A rigorous testing schedule must be maintained to ensure that there are no shorts, especially in impressed current systems. Many systems have failed as a result of the presence of shorts. MONITORING AND MAINTENANCE The respondents in the survey have made it clear that monitor- ing and maintenance of the cathodic protection system is too burdensome and that most agencies are finding it difficult to cope with this process. Initial cost and monitoring are the fac- tors that discourage the application of cathodic protection sys- tems. Of the twenty-four respondents who have at least one cathodic protection system, only 10 monitor them as summa- rized in Table 17 in chapter four. Therefore, 14 agencies do not monitor their cathodic protection systems. Among the respon-

37 dent states, only five monitored all of the systems, with another four monitoring only some. The province of Ontario indicated that owing to downsizing of the government and the outsourcing of maintenance, it is concerned about its ability to monitor and maintain impressed current systems and are more inclined to use galvanic systems in the future. Texas does not believe it can monitor and maintain the systems and therefore does not use them. Utah had a total of seven systems, all of which failed because they were not able to monitor and main- tain them and also because personnel involved with those pro- jects are no longer with the department and very little if any information is now available. Only nine agencies indicated that they have at least one person to monitor their cathodic protection systems and five believed that they had sufficient staff to monitor all of their systems. Monitoring and mainte- nance being a significant burden was selected by the most respondents (12) as a reason for not selecting cathodic protec- tion systems in the future as noted in Table 21. Ohio, which had started to use cathodic protection systems in the 1980s, has lost all personnel who were familiar with the systems and at present even status information on these systems is not available to the agency. Site visits by the SHRP team before 1992 uncovered some systems that were believed by the agencies to be oper- ational, but had either failed or were powered off (51). The owners did not have the correct information on the systems in their jurisdiction. Under FHWA Demonstration Proj- ect 84, similar experiences were discovered in several states. Agencies believed that their systems were opera- tional when, in actuality, they were not. In one instance, the present staff of the agency did not even know that they had a cathodic protection system in their jurisdiction. Table 22 summarizes the responses to the question that asked if the agency was aware of the status of the cathodic protection systems they have. Seven of the 22 respondents to Question 42 (Table 23) indicated that they had less than 5% of their cathodic protec- tion systems operational. In Question 47 (Table 24), most respondents believed that the failure of their cathodic protec- tion systems could be attributed to insufficient current output by the system owing to improper settings. Improper current settings are a symptom of inadequate monitoring and main- tenance and can be easily rectified and not be a reason for the inadequate performance. Many of the disappointing experiences have resulted from failure of systems as a result of insufficient monitor- ing and maintenance; many agencies simply do not have the resources. Some agencies installed systems for non-technical reasons. As their understanding of the technology and their confidence in its ability to provide protection were inadequate, sufficient motivation did not exist to allocate the necessary resources. In some instances, the agencies did not appreciate Reason No. of Respondents Cathodic protection system did not work at all Cathodic protection did not stop corrosion and concrete repairs were required after cathodic protection installation within the first 5 years 0 Cathodic protection components failed and could not be maintained 7 Monitoring and maintenance was a significant burden 13 The agency does not have the resources to monitor and maintain the cathodic protection system 7 The technology is not well understood by the agency 3 The consultants are not well versed in the technology to recommend it to the agency 1 Applicators and contractors that do business with the agency do not have any experience with the technology 2 Experience of other agencies suggest cathodic protection is too complicated, does not work, is too expensive, and requires significant monitoring and maintenance 1 Agency staff with experience in cathodic protection has retired or have been promoted and new staff have no experience with cathodic protection 2 Cost of cathodic protection was relatively higher then other options 10 3rehtO Note: Table based on results of Question 31 of the survey. 3 TABLE 21 NOT INCLINED TO USE CATHODIC PROTECTION IN THE FUTURE oNseYnoitseuQ Is the current status of operation of all or some of the cathodic protection systems available to the agency? 11 11 While they were operational, did the cathodic protection systems stop corrosion and extend the remaining service life of the reinforced concrete component? 15 2 24?denimretedneebesuacasah,tonfI Note: Table based on results of Questions 41, 44, and 45 of the survey. TABLE 22 STATUS AND OPERATION OF CATHODIC PROTECTION SYSTEMS % Cathodic Protection Systems No. of Responses 5 7 20 0 40 2 60 2 80 4 100 7 Note: Table based on results of Question 42 of the survey. TABLE 23 PERCENT OF SYSTEMS OPERATIONAL

the need for monitoring and maintenance. The Technical Committee of NACE reported that “In many cases the way CP [cathodic protection] is sold today, the client/owner is not informed of the need for future maintenance of the CP System. The client/owner must know up front that an inspection/monitoring program is required. This must be addressed in the scope of work. This area should be addressed in a NACE document” (52). PERFORMANCE AND DURABILITY OF SYSTEM COMPONENTS Performance and durability of the anode materials is crucial to the overall success of the cathodic protection systems. All anodes have some performance and durability limitations; for example: • Conductive polymer material used as secondary anodes is susceptible to acid attack, • Conductive paint can weather within 5 to 10 years depending on the exposure conditions, • Mixed metal oxide anodes when operated above 10 mA/ft2 of anode surface area can generate chlo- rine, which can result in acid attack of the concrete, • Zinc anodes can passivate in certain environments, • Ceramic anodes can have low contact resistance and if the gasses are not vented properly can result in acid attack, • Adhesive in the zinc foil anodes can dissolve and loss of bond can occur if water infiltrates, • Coke breeze systems can suffer from high resistance due to loss of coke around anodes and corrosion of wire connectors, and • Arc sprayed zinc and aluminum–zinc–indium alloy may experience bond problems, etc. 38 Therefore, anode materials and the configurations in which they are used must be selected, designed, and installed in accor- dance with the best practice and the system operated within safe operating ranges. The survey queried the respondents on time to failure of most commonly used cathodic protection systems. The pri- mary reason for this question was to try and ascertain the experience agencies have had with cathodic protection. The question did not distinguish between premature failure and end of service life. Therefore, some agencies reported both and some responded only if the systems were considered to have failed prematurely. In reviewing the durability of anode materials, it is impor- tant to understand that whereas some agencies have reported failures for certain systems others have very successfully applied them. Many failures of cathodic protection systems occurred when (1) experimenting with new systems; (2) agen- cies installed systems without requisite experience and knowl- edge; (3) systems were not matched to the structure or the environment, improperly designed, or incorrectly installed; and (4) systems were not monitored or maintained appro- priately. A distinction must be made between designed consumption or weathering of an anode and durability. For example, when arc sprayed zinc is completely consumed, it does not signify failure of the system; it is simply time to replace the anode. However, if the anode debonded or became passive then it would be considered a failure. As discussed in chapter four, the ferex anode systems did not exhibit sufficient durability for use in reinforced concrete structures and failed within 5 years, which was reported by several respondents. Missouri reported failure of conductive polymer systems at 0 to 5 years when carbon fibers were used as the primary anode. However, the conductive poly- mer anode systems using platinum as the primary anode have lasted between 21 and 25 years. Missouri now only uses plat- inum as the primary anode in conjunction with conductive polymer anodes. Failure of the conductive coke asphalt system was reported by four agencies, Missouri (11 to 15 years), North Carolina and Virginia (0 to 5 years), and Ontario (6 to 10 years). The failure in Virginia was judged to have resulted from acid generation at the anode. In addition, coke asphalt systems are susceptible to damage during replacement of the riding surface (some operational systems have been lost during replacement of the asphalt riding surface). This is an inher- ent flaw in the design of this type of system and it is not used any more. Failure of a zinc foil with adhesive system was reported by five agencies; three had experienced failure in the 0- to 5-year time frame and two in the 6- to 10-year time frame. Florida, Illinois, and Missouri reported failure of the adhesive and loss of bond. High rate of anode consumption at the edges was Reasons for Failure No. of Responses Failure of cathodic protection components resulted in the system being not operational for more than 20% of the time 8 Cathodic protection system not putting out sufficient current owing to improper design 0 Cathodic protection system not operational owing to failure of one or more components 1 Cathodic protection system not putting out sufficient current owing to improper settings 10 Cathodic protection system did not operate owing to deficient design 2 Cathodic protection system not installed as designed 1 Anode not appropriate for the application 0 Vandalism damaged system components 5 5deifitneditoN Note: Table based on results of Question 47 of the survey. TABLE 24 REASONS FOR FAILURE OF CATHODIC PROTECTION SYSTEMS

39 The durability of the rectifier is dependent on several factors. As discussed earlier, lightning strikes on a rectifier are a significant problem and 10 agencies noted that to be one of the most important problems. The rectifying ele- ment, the control cards, and the remote monitoring units were identified by the agencies to be the components most susceptible to failure in the rectifier. Their responses to this question are tabulated in Table 28. In the interview, Missouri indicated that certain rectifiers have performed better than others and have been operational for the entire service life of the system. Vandalism is also an issue that must be considered during design. Placing system components out of reach of vandals is essential. At least one agency has reported the failure of a system as a result of vandalism. In one instance, it was found that homeless people living under a bridge had cut the con- duit and wires for the cathodic protection system in an effort to obtain power for their heaters and television sets. North Carolina installed five different types of impressed cathodic protection systems, the mixed metal oxide mesh, con- ductive paint, conductive polymer, conductive coke breeze, and aluminum–zinc–indium alloy, on five different bents and all of them failed within one year. The mode of failure for each of the five systems was listed as “whole system failed.” In the rectifier experience section they indicated that they had problems with the rectifier and the control cards. They also commented that these systems were not considered “tough reported by Oregon. Missouri indicated that in year 1 the bond failure was noted, and by year 4 the anode was consumed. This anode is no longer available. Florida reported failure of the localized (hockey puck) zinc anodes in 0 to 5 years, as the anodes did not provide adequate protection in their application. Most agencies indicated that on average cathodic protection systems were operational for 5 to 15 years. Three agencies, New Brunswick, Missouri, and Washington State, indicated that their systems lasted more than 15 years. A summary of the responses to this question is provided in Table 25. It may be noted that with a few exceptions, not many agencies have systems old enough to have been operational for more than 15 years. The rectifier on an impressed current system can often be the weakest link and requires the most maintenance. Several agencies that reported failure of various kinds of systems indicted that the failure had occurred as a result of the fail- ure of the rectifier. It was selected by the greatest number of respondents to require the most maintenance (Table 26). Cables, wiring, and conduits were also identified by the same number of respondents. However, the rectifier is easy to repair or replace and is not a fatal flaw. The cable, wiring, and con- duit failure, where they are embedded in concrete, could turn out to be a fatal flaw. A maintenance frequency of once a year was experienced by the most number of respondents as the summary in Table 27 indicates. Length of Operation No. of Responses Less than 1 year 2 1 to 5 years 3 5 to 15 years 15 Greater than 15 years 3 Note: Table based on results of Question 43 of the survey. TABLE 25 LENGTH OF OPERATION OF CATHODIC PROTECTION SYSTEMS .oNtnenopmoC 6reifitceR 3tinUgnirotinoMetomeR 1edonA 6tiudnoCdna,gniriW,elbaC 1slleCecnerefeR 0seborPtnerruC Concrete Overlay or Backfill Material Used to Encapsulate the Anode 1 Note: Table based on results of Question 48 of the survey. TABLE 26 CATHODIC PROTECTION COMPONENTS THAT REQUIRE THE MOST MAINTENANCE Frequency No. Once a week 0 Once a month 1 Once a quarter 0 Once every six months 2 Once a year 7 Once every two years 2 Once every five years 4 Note: Table based on results of Question 49 of the survey. TABLE 27 FREQUENCY OF CATHODIC PROTECTION COMPONENT MAINTENANCE .oNtnenopmoC Rectifying Element Failure 8 7eruliaFdraClortnoC 01sekirtSgnithgiL Remote Monitoring Unit Failure 6 6rehtO Note: Table based on results of Question 52 of the survey. TABLE 28 RECTIFIER COMPONENTS MOST SUSCEPTIBLE TO FAILURE

40 Factors No. of Responses Better understanding of the technology by agency staff 15 4stnatlusnocehtfonoitacudE Trained applicators and contractors Reduction in cost of the cathodic protection system 22 Availability of consultants to monitor and maintain cathodic protection systems 9 Improved technology to monitor and maintain systems 20 Improved quality of the system components that would reduce the frequency of repair and maintenance of cathodic protection components 17 11ngiseddevorpmI Technical assistance in selection of appropriate cathodic protection systems for each application 13 8evobaehtfollA Note: Table based on results of Question 53 of the survey. 4 TABLE 29 FACTORS THAT WILL ENCOURAGE APPLICATION OF CATHODIC PROTECTION SYSTEMS enough for severe bridge environments.” This is in contrast with the experience of other states such as California, Florida, Missouri, and Oregon and in Canadian provinces such as Alberta, New Brunswick, and Ontario, who among them have a total of 464 bridge structures with cathodic protec- tion systems. A majority of all systems in Florida are in the marine environment. Many of the systems in the northeast- ern provinces of Canada are in very aggressive marine and deicing salt environments. Missouri itself has mixed metal oxide and conductive polymer anode systems that have been operational for at least 19 years. Many of the problems and failures of cathodic protection systems discussed previously are symptomatic of the evolution of anode materials and the process of learning the material interactions and limitations. With the exception of the con- ductive coke asphalt, ferex anode, and the zinc foil anode, all other anodes are still successfully being used. Several differ- ent types of systems, both galvanic and impressed current, have been in operation for approximately 20 years. INITIAL AND LIFE-CYCLE COST A majority of the respondents indicated that the initial cost of the cathodic protection systems is relatively high. Many are not convinced that the cost-benefit ratio is favorable. Some agencies indicated that they would like to see documentation of performance for each type of cathodic protection system and a listing of both initial and operating costs. Some indicated that the quality of the products available needs to be improved and the cost lowered for cathodic protection to be an attractive alternative for them. Several also indicated that more innova- tion and competition in the marketplace is desired. The second generation of bridge structures (bridges built after the 1970s) include improvements to design such as an increase in cover, lower permeability concrete, use of epoxy- coated rebars, use of admixed corrosion inhibitors, etc. Cali- fornia uses a polyester concrete wear surface on bridge decks that can be expected to provide a reasonably good level of waterproofing and it can also be replaced overnight with min- imal traffic delays. These techniques do provide a reasonable extension in service life. Therefore, on this generation of struc- tures, the need for cathodic protection will occur at a much later date. If we use the solution to Fick’s Second Law of Dif- fusion and estimate the impact of cover and diffusion coeffi- cient on time-to-corrosion initiation, we find that the increase in cover results in an exponential increase in time to corrosion. Similarly, the impact of improving the permeability, and to some extent diffusivity, also increased time-to-corrosion initi- ation exponentially. When both are combined the impact is more dramatic. Most agencies are very comfortable with barrier sys- tems such sealers, concrete overlays, and waterproofing membranes. The initial costs of cathodic protection will generally be higher compared with these technologies. The distinguishing factor between cathodic protection systems and barrier systems is that at the end of the service life of the cathodic protection system there is no corrosion- induced damage. Whereas barrier systems gradually fail and at the end of their service life, some chlorides have migrated into the concrete and corrosion-induced damage has occurred. CATHODIC PROTECTION MARKET The size of the present cathodic protection market is not suffi- cient to generate competition and drive innovation. There are only a few vendors and they do not necessarily focus on the same market segment and therefore competition is virtually non-existent. The sale of the system is dependent on the own- ers already having faith in their products or their sales people convincing them of the benefits of its use. Even the consulting arena is quite limited as manufacturers and installers find it easier to sell design-build projects. The lack of demand for post-installation services also is not very helpful to the growth of the industry. The majority response from the industry indi- cated that the industry is in decline. However, one vendor noted that they expect to install cathodic protection systems on 200 bridges in the next five years. They also indicated that they have been involved with the either the supply of materials, installation of the systems, or providing consulting and engi- neering services for cathodic protection on 1,350 bridges since 1980. Because the number of structures reported by state and provincial agencies is less than half that figure, it is assumed that many of those structures are located outside of North America or are not owned by state and provincial agencies. As this vendor is a large international corporation, their sales fig- ures and future projections are a clear indication of where the

41 rest of the world is going with this technology. In North Amer- ica, the cathodic protection industry for bridge structures is somewhat weak. These numbers also provide insight into the marketplace in terms of monopoly and lack of competition. When agencies were questioned as to which factors will encourage the application of cathodic protection technology, reduction in cost was cited by the greatest number of agencies. In the summary of the responses presented in Table 29, reduc- tion in cost is closely followed by improved technology to monitor and maintain, improved quality of system components, improved understanding of the technology, and technical assis- tance in selection of appropriate cathodic protection systems. Thus, for the growth of the market, more innovation and com- petition is required to reduce costs and improve the monitoring systems and quality of the components. The industry and tech- nical associations will have to do more to provide better direc- tion in the selection process and design of the systems.