Corrosion prevention and control pdf
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Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Much of the chapter is dedicated to the choices made by designers and maintainers of steel bridges based on the synthesis survey and supplemental literature.
Subsequent sections of this report go into greater detail regarding uncoated steel weathering grades and stainless steels and coated steel including liquid coatings, galvanizing, and metallizing. Corrosion-Prevention Options When one considers corrosion-prevention options for bridge structural steel, it is helpful to recognize the corrosion-prevention mechanism, degradation of that protection, and even- tual repair or maintenance needs. Table 1 provides an overview of four primary corrosion- prevention strategies.
Later sections of this report discuss coated and uncoated steel options in more detail. Designing for Corrosion Prevention Figure 2 graphically presents the responses provided by designers regarding the most com- monly used corrosion-prevention technologies. Based on the survey, zinc-based coating systems and weathering steel are the most common corrosion-prevention schemes. Figure 3 shows the average percentage of bridges designed with some use of each technology assuming the midpoint of the percentage range for each response category.
Of the states responding to the design section of the survey, a slight majority addressed cor- rosion differently based on environmental or operating conditions. Issues that are typically considered included average daily traffic, difficulty of access, climatic conditions humidity , use of deicing salts, proximity to the coast, height above water, tunnel-like conditions, ownership state versus C H A P T E R 2 Corrosion Prevention and Control for Steel Bridges.
Protection Mechanism Functional Mode of Degradation Repair Methods Coated steel Protective film isolates steel from corrosive elements Protective coating is breached, typically caused by mechanical damage, weaknesses in the applied film e. Maintenance painting or coating removal and replacement Uncoated weathering steel Forms corrosion patina, which reduces steel corrosion rate to a tolerable level Corrosion patina becomes damaged or disrupted because of local exposure conditions or mechanical damage.
Painting or steel replacement Galvanized steel Metallurgically bonded zinc protects steel through barrier and sacrificial mechanisms. Galvanizing corrodes, reducing the zinc thickness.
Maintenance painting or thermal spray application Metallized steel Sprayed metal coating zinc, aluminum, or alloys thereof mechanically bonds to and protects steel through barrier and sacrificial mechanism Metallizing corrodes or undercuts at weaknesses in the applied film e. Maintenance painting or thermal spray application Table 1. Representative corrosion prevention methods for steel bridges.
Figure 2. Survey results for corrosion-prevention technology usage. Corrosion Prevention and Control for Steel Bridges 9 Four respondents from Kansas, New York state, Connecticut, and Maryland reported using specific corrosion allowances in new bridge design for weathering steel structures; one of those respondents Maryland also indicated corrosion allowances for painted steel structures are used.
The most common innovative practice reported by bridge designers was the use of metallizing or galvanizing. Florida reported a great interest in coatings with improved gloss and color retention. The most common reported research need by designers included issues related to maintenance decision making when to replace coating system, how to cost-effectively maintain, how much corrosion can be tolerated when aesthetics are not a concern.
A better understanding of the effects of deicing salts and the need for less-corrosive deicing materials was also a reported research need. Alternatives with sig- nificantly e. Generally, if an analysis shows that a strategy is cost-effective in one situ- ation, it is presumed to be cost-effective in similar situations. Most of the states did not require corrosion maintenance procedures as part of the design, although one state Rhode Island indicated designers are required to provide recommended corrosion maintenance procedures for coated steel structures.
Figure 4 shows how frequently designers and maintainers consider corrosion as the limiting factor for the service life of steel bridges. Maintainers consider corrosion to be a more significant Figure 3. Most popular corrosion-prevention technologies. Roughly one-third of the designers responding said corrosion was the limiting factor for design service life of steel bridges most of the time versus roughly one-half of the maintainers.
Warranties for Corrosion Control Corrosion-control warranties are sometimes used to help ensure the quality of industrial paint- ing projects including bridges.
A report discussed warranty clauses for bridge paint con- tracts in considerable detail Chang and Georgy b. As a practical matter, warranties are usually written for a time period considerably shorter than the anticipated coating service life e.
Warranties generally require painting contractors to repair coating breakdown above some level during the warranty period. There appears to be a wide range of details behind the warranty requirements. For example, some warranties have relatively detailed criteria clarifying the type of unacceptable defects and the affected area thresholds that invoke the need for repair. Others have more gener- alized statements.
Some warranties explicitly call for an inspection by the DOT and contractor, whereas others are silent on the issue. Figure 5 shows that most of both maintainers and designers do not believe warranties effec- tively extend the life of steel bridge corrosion prevention. Only one designer respondent Maryland reported using warranties specific to corrosion prevention in new bridge construction contracts.
Survey results regarding corrosion as a life-limiting factor for steel bridges. Corrosion-Control Maintenance Corrosion-control maintenance primarily involves cleaning and painting bridges. The use of galvanizing and metallizing topped the list of reported innovations.
Also included were removal of pack rust with ultrahigh-pressure water jetting, innovative surface preparation methods vapor blasting and laser paint removal , and innovative coating chemistries including fluoropolymer, calcium sulfonate, and waterborne acrylic. One respondent reported that the agency requires inspectors to perform an electrical holiday test on representative coated areas to reduce the num- ber of pinholes and defects. Maintainers reported success with drain extensions, bridge washing, and preventive maintenance programs.
Challenges exist with overcoating and the cost of inspect- ing spot-coating work. The decision to perform maintenance is most commonly a condition-based decision. For both painted and unpainted steel bridges, users identifying as maintainers reported that inspec- tion recommendations and coating condition code most commonly drive corrosion mainte- nance.
The survey results suggest that routine inspections are generally adequate for identifying corrosion maintenance needs on both coated and uncoated steel structures.
In some cases, the supplemental inspections were used to populate a condition database separate from Figure 5. In other cases, the supplemental inspections were intended to define maintenance needs for planning and execution more thoroughly. For those who addressed corrosion differently based on environmental or operating conditions, most did so based on assessments of the individual bridge rather than through written policies.
Figure 6 shows the various ways that agencies determine budget needs for corrosion mainte- nance. Most users reported that corrosion maintenance competes with other bridge maintenance needs for funding. For bridge painting by contract forces, steel bridge corrosion maintenance competes with other bridge maintenance needs.
Figure 7 illustrates the issues that affect what corrosion-related maintenance actions are taken. Lowest LCC and the availability of federal funding were more likely to drive corrosion-related maintenance decisions than were user impact or lowest construction cost.
Figure 6. Survey responses regarding budgeting for corrosion maintenance. Survey responses regarding corrosion-maintenance decision drivers. Maintaining Coated Steel Bridges Figure 8 shows the percentage of responding agencies that use each of the various corrosion- control technologies when maintaining a coated steel bridge.
Spot repairs with a full overcoat appear to be less com- mon than spot repairs. About half of the states responding performed washing or rinsing to remove contaminants as a maintenance technique. Spot painting and washing were performed in-house by a significant percentage of the states, but contracting work using state specifications was the most common mechanism for performing steel bridge maintenance.
Table 2 shows the range of estimated service life or recurrence interval provided by the respondents. Figure 9 illustrates how frequently various conditions dictate the need to repaint a coated steel bridge. The primary driver is condition-based inspection recommendation or poor coat- ing condition rating versus time-based. It does appear common that corrosion maintenance is performed at least in part to coincide with other work.
Maintaining Uncoated Steel Bridges Figure 10 shows the percentage of responding agencies that use each of the various corrosion- control technologies when maintaining an uncoated steel bridge.
Thirty-eight percent of the respondents reported that they had cleaned and repainted an entire weathering steel structure, although one respondent noted that this occurs infrequently. Washing is performed in-house by a significant percentage of the states, but contracting work using state specifications was the most common mechanism for maintenance painting of uncoated steel. Table 3 shows estimated service life provided by the respondents.
Figure 11 illustrates how frequently various conditions dictate the need to perform corro- sion maintenance on an uncoated steel bridge. The primary driver is condition-based inspec- tion recommendation, poor coating condition rating, or observed steel section loss versus. Agencies reporting that they use various corrosion-control technologies for coated steel bridge maintenance.
Reported service life for coated bridge maintenance strategies. Corrosion Prevention and Control for Steel Bridges 15 How frequently does each of the following conditions contribute to the need for repainting a coated steel bridge? Figure 9. Conditions dictating the need to repaint a coated steel bridge.
Figure Agencies reporting that they use various corrosion-control technologies for uncoated steel bridge maintenance. Reported service life for uncoated bridge maintenance strategies. Conditions dictating the need to maintain an uncoated steel bridge. Relative Cost The cost of various corrosion-prevention schemes is dependent on multiple factors.
Con- sequently, there is not a clear option for the lowest installed cost. Maintenance considerations vary considerably as well, making LCC calculations even more complicated. For the purposes of perspective, a TRB presentation provided the data in Figure 12 Medlock The chart provides the relative cost of a ft continuous two-span bridge with varying corrosion- prevention schemes.
The structure consists of 30, in. The cost does not include abutments, site work, installation, and so forth. Relative fabricator cost for a hypothetical as-delivered steel structure with various corrosion-control strategies.
Of course, each material alternative will have different LCCs that should be considered when designing a bridge. Another study looked at the relative cost and performance of various coating maintenance strategies on a New Jersey bridge over saltwater Ault and Farschon The data suggest a trend toward increased performance with increasing cost, but the relationship has considerable scatter.
Corrosion Prevention and Control
Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Much of the chapter is dedicated to the choices made by designers and maintainers of steel bridges based on the synthesis survey and supplemental literature. Subsequent sections of this report go into greater detail regarding uncoated steel weathering grades and stainless steels and coated steel including liquid coatings, galvanizing, and metallizing.
Corrosion Engineering by Pierre Roberge pdf. Summary: Publisher's Note: Products purchased from Third Party sellers are not guaranteed by the publisher for quality, authenticity, or access to any online entitlements included with the product. The Latest Methods for Preventing and Controlling Corrosion in All Types of Materials and Applications Now you can turn to Corrosion Engineering for expert coverage of the theory and current practices you need to understand water, atmospheric, and high-temperature corrosion processes. This comprehensive resource explains step-by-step how to prevent and control corrosion in all types of metallic materials and applications-from steel and aluminum structures to pipelines. Filled with illustrations, this skills-building guide shows you how to utilize advanced inspection and monitoring methods for corrosion problems in infrastructure, process and food industries, manufacturing, and military industries. Following the same format as the highly successful Volume 1, Volume 2 applies the principles of deformation to the analysis of folds and fractures.
This handbook represents the second edition of a corrosion handbook first published in July by AMMTIAC's immediate predecessor; the. Advanced Materials.
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Corrosion Prevention by Protective Coatings, Third Edition
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