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In other terminology, corrosion is the wearing away of metals due to a chemical reaction. By 1975 the cost of corrosion on automobiles was estimated to be $16 billion, roughly 20% of the total cost of corrosion that year. In order to evaluate new and existing supplies for use in automotive applications, many accelerated test procedures were developed. Accelerated test procedures include those that were performed in laboratory cabinets and on specifically designed proving grounds. Laboratory cabinet testing is a relatively inexpensive way to obtain corrosion performance on components and to compare alternative materials. Proving ground testing is considerable more expensive, but allows one to evaluate all of the materials as a complete system, including typical input stresses that a vehicle experiences. Of course, service exposure data would be necessary to correlate the field testing to the intended service environment. Certain metals are more intrinsically resistant to corrosion than others, either due to the fundamental nature of the electrochemical processes involved or due to the details of how reaction products form. If a more susceptible material is used, many techniques can be applied during an item's manufacture and use to protect its materials from damage. Successful organisations cannot tolerate major corrosion failures, especially those involving personal injury, fatalities, unscheduled shutdowns and environmental contamination. Typically, once a system, a plant or any piece of equipment is put into service, maintenance is mandatory to keep it operating safely and efficiently. This is particularly true for aging systems and structures, many of which may operate well beyond the original design life. Accelerated Corrosion tests are tests that are used to evaluate a material or system for long-term performance in a reduced timeframe . Test methods vary depending on estimated service (simulate this environment) , tests can incorporate single or multiple factors and are designed to stress samples to determine performance in a reduced period. Characterizing deterioration of reinforced iron structures caused by the corrosion of steel bars is a major problem in predicting service life. Normally, the galvanostatic method is used for accelerating steel bar corrosion in concrete. The surface characteristics of the corroded steel bar, however, are found to be different when the corrosion is induced by galvanostatic method or by natural environment. Recently, an artificial climate environment has been used to accelerate reinforcing bar corrosion in concrete. This method is becoming important in assessing the durability of concrete structures because of the similarity in surface characteristics of the corroded steel bar under natural and artificial climate environments. How do these Tests Benefit? Tests are used as a decision making tool , highlight potential deficiencies in a material or system , make easy to evaluate an alternative or replacement materials , and allows for system changes before production/implementation
Article Source: http://www.bharatbhasha.net Article Url: http://www.bharatbhasha.net/science.php/210028 Article Added on Monday, February 1, 2010
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