CORROSION |
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Stress Corrosion Corrosion Fatique Fretting Corrosion Heat Treatment |
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List of Agent |
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Acids. In general, moderately strong acid will corrode most of the alloys used in airframes. The most destructive are sulfuric acid ( battery acid ), halogen acids ( hydrochloric, hydrofluoric and hydrobromic ) and organic acids found in the wastes of humans and animals. Alkalies. Although alkalies as a group are generally not as corrosive as acids aluminum and magnesium alloys are exceedingly prone to corrosive attack by many alkaline solutions unless the solutions contain a corrosion inhibitor. Particularly corrosive to aluminum are washing soda, potash ( wood ashes ), and lime ( cement dust ); however, one alkali, amonia, is excepted because aluminum alloys are highly resistant to it. Magnesium alloys also are resistant to alkaline corrosive attack - they develop a protective film when exposed to caustic alkaline solution. Salts. It is difficult to generalize about salts, are corrosive agents. However, most salt solutions are good electrolytes and can premote corrosive attack. Some stainless steel alloys are resistant to attack by salt solutions but aluminum alloys, magnesium alloys and other steels are extremely vulnerable to some solutions containing salts. Exposure of airframe materials to salts or their solutions is extremely undesirable. The Atmosphere. The major atmospheric corrosive agents are oxygen and airborne moisture, both of which are in abundant supply. Corrosion often results from the direct action of atmospheric oxygen and moisture on metal, and the presence of additional moisture often accelerates corrosive attack, particularly on ferrous alloys. However, the atmosphere is also cluttered with many other corrosive gases and contaminates. Two specific type industrial and marine atmospheres are unusually corrosive. Industrial atmospheres Contain many contaminants, the most common of which are partially oxidized sulfur compounds. When these sulfur compounds combine with moisture, they form sulfur based acids that are highly corrosive to most metal. In areas where these are chemical industrial plants, other corrosive atmospheric contaminants may be present in large quantities, but such conditions are usually confined to a specific locality. Marine atmosphere. Contain chlorides in the form of salt particles or droplets of salt-saturated water. Since saline moisture is electrolyte, it provides an excelenct medium for corrosive attack on aluminum and magnesium alloys which are vulnerable to this type of environment. Water. The corrosivity of water will depend on the type and quantity of dissolved mineral and organic impurities and dissolved gases ( particularly oxygen ) in the water . Physical factors such as water temperature and velocity also have a direct bearing on the corrosivity. The most corrosive of natural waters. ( sea and fresh waters )are those that contain salts. Water in the open sea is extremely corrosive, but waters in harbors are often even more so becouse they are contaminated by industrial waste and are diluted by fresh water. The corrosivity of fresh water varies from locality to locality due to the wide variety of dissolved impurities that may be present in any particular area. However, soft water and rain water are usually considered to be very corrosive. Hard waters tend to be less corrosive to most metals because they are alkaline, but some metals such as alloys of aluminum and magnesium seem to be allergic to alkaline waters and corrode readily. read more...
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List of Agent |
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| Corrosion of fereous metals. | ||||
| One of the most familiar types of corrosion is ferrous oxide,.. | ||||
| Corrosion of aluminum and aluminum alloys. | ||||
| Corrosion attack on aluminum surfaces is usually quite obvious,. | ||||
| Corrosion of magnesium alloys. | ||||
| Magnesium is the most chemically active of the metals used,. | ||||
| Treatment of titanium and titanium alloys. | ||||
| Attack on titanium surfaces is generally difficult to detect | ||||
| Protection of dissimilar metal contacts. | ||||
| Certain metals are subject to corrosion when placed in contact with other metals | ||||
| Processes and materials used in corrosion control | ||||
| Aircraft parts are almost always given some type surface finish | ||||
| Chemical treatment. | ||||
| Parco Lubrizing in a chemical treatment for iron and steel parts | ||||
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Copyright @ 2007 |
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