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Results
Factors in the Cost of Corrosion for Naval Vessels
Clayton, Norman J. (David A. Shifler, NSWC) | Needham, William (NSWC) | Shifler, David A. (NSWC)
ABSTRACT The United States Navy operates and maintains over 300 ships and submarines in a highly aggressive marine environment. The corrosion of ship structures and shipboard systems and components in this environment is one of the biggest contributors to the Navy?s maintenance costs. This paper will provide an overview of the marine environment as it affects naval vessel corrosion problems, and provide several examples of major corrosion cost drivers according to a hierarchical work breakdown structure of ship structures and functional systems. The maintenance documentation and data collection processes at the organizational, intermediate and depot levels will be presented, along with an assessment of their ability to be used to identify and extract material, labor, and incidental costs associated with corrosion prevention and repair. This overview will discuss the difficulties in gathering corrosion data and in the use of existing data for determining the cost of corrosion. A quantitative measure of the cost of ship corrosion to the Navy must be based on the extrapolation of limited data qualitatively derived and assessed by knowledgeable corrosion engineers in conjunction with Fleet maintenance personnel. A methodology that has been successfully demonstrated for addressing corrosion costs based on limited quantitative input from the naval maintenance community will be presented. INTRODUCTION People and organizations involved in corrosion prevention, control, and repair activities in all types of industries have always required reasonably accurate estimates of the costs of corrosion in order to provide persuasive cost/benefit analyses. On a problem-specific or company-specific scale, the current cost of a particular corrosion problem is required to perform life cycle cost (LCC) estimates or return on investment (ROI) calculations to help choose between one or more possible corrective actions. On a much broader industry-wide or national scale, estimates of the cost of corrosion can be used to demonstrate the impact of corrosion on the industry or economy, and the need for investment in facilities, training, research, and policy. For these reasons, the results of the United States national cost of corrosion studies are widely publicized and frequently cited in the introduction of many corrosion engineering papers and articles. There have been three such studies since 1975, with the most recent concluding in 2001 and publicized in 20021-3. A summary publication was produced to accompany the recent 2001 study4. There were two main approaches taken in the 2001 study4: summing the incurred or expended costs spent on corrosion control methods and contract services, and determining the costs for specific industry sectors. The corrosion control methods approach included the costs of coatings application, and the use of corrosion resistant materials, corrosion inhibitors, and cathodic protection, while contract corrosion control service costs included engineering, research and development, and training. The industry-specific approach divided industry into five categories containing 26 sectors. The actual data collection focused on direct costs, defined as those incurred by owners or operators of structures, equipment, or facilities, the manufacturers of products, and the suppliers of services. Indirect costs were estimated, as they are more complex and variable according to the industry sector. Indirect costs include accelerated depreciation and various intangibles. For military assets, decreased readiness, similar to downtime in a production industry, and degraded mission capability are key factors. Indirect military costs also include the cost of building and maintaining corrosion control facil
- Materials > Metals & Mining (1.00)
- Materials > Chemicals (1.00)
- Government > Regional Government > North America Government > United States Government (1.00)
- (2 more...)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
ABSTRACT The free flood areas of underwater vehicles pose a significant and expensive corrosion problem to operating forces. These areas undergo an alternating cycle of wetting and drying in a closely confined area that has regions of relatively stagnant seawater and other regions of high turbulence. The corrosion induced damage requires constant upkeep by ship.s force and frequent expensive maintenance action by depot personnel to effect periodic full restoration. Modifications to the superstructure area of underwater platforms are contemplated that will reduce the accessibility of this region for periodic maintenance. An improved coating system is therefore needed to increase the longevity of the current system from about 5 years to 20 years, corresponding to the mid life major overhaul availability. A three-phase program of coating evaluation was developed to address this need. This report provides the results of the first two phases of the program. The first phase consisted of the development of key attributes necessary for an improved coating system and the screening of available commercial coating products. The second phase consisted of a series of mechanical properties testing and corrosion testing to select out the best candidates for a final phase of at sea and long term corrosion performance testing. INTRODUCTION The free-flood areas of underwater platforms are highly susceptible to corrosion. This is due to a number of contributing factors. These areas are subjected to alternating cycles of wetting and drying with seawater, the worst kind of immersion service. Cyclic immersion is one of the most aggressive tests used by corrosion engineers to compare materials and coating systems for their resistance to a seawater environment. In addition, these areas have a wide range of seawater flow regimes, ranging from nearly static to turbulent. The static condition results in the creation of localized corrosion cells that are autocatalytic in that they create an increasingly corrosive environment, ultimately creating deep pits and/or crack initiation sites at crevices. The turbulent condition results in the gradual eroding of protective coatings and/or films that then exposes substrate bare metal to electrochemical and erosion- corrosion degradation. The free flood areas are subject to extremes of temperatures and pressures. Finally, the free flood area is held rigidly in place with an extensive system of stiffeners, plates and fasteners. This creates a complex geometry with myriad sharp corners and edges that serve as corrosion initiation sites due to the difficulty in applying protective coatings in these locations. The coating system originally specified for the free flood areas of underwater platforms is the epoxy-polyamide paint manufactured according to MIL-DTL-24441. It is an excellent general-purpose paint, but it is not a very good paint for this application. Due to the uniquely aggressive environment in these areas, it starts to break down and is in need of touch up repair after as little as six months of service. This requires frequent access to the area by Ship.s Force or Intermediate Maintenance Activity (IMA) personnel to effect repairs. The coating system must be completely removed and recoated at approximately 5-year intervals to prevent significant metal loss due to corrosion. Redesign of the superstructure will result in a reduction in the accessibility of the free flood area for coating touch-up and repairs. Over the last several years, the development of high solids epoxies has significantly extended coating longevity for immersion service applications, resulting in a substantial cost savings to the N
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)