Attention should be paid to fatigue vibration corrosion and its prevention methods

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Moiré corrosion is also a special form of wear corrosion; it refers to the degradation that occurs at two surfaces in contact under load due to vibration and sliding (repeated relative motion), and is also known as micro-vibration corrosion. The damage caused by vibration-induced corrosion is extremely severe; it not only destroys precision metal components, but the resulting oxidized rust also causes those components to become stuck. Furthermore, it leads to contact surfaces exceeding allowable tolerances, and the corrosion pits that form can result in fatigue fractures. The most common example of fatigue corrosion is between the bearing races and the shaft, and it also occurs in engine components, locomotive parts, and components connected by bolts. Its necessary condition is repeated relative motion; a displacement as small as 10-8 cm can cause damage. For example, in long-distance railway and ship transportation, car axles are subjected to loads on their surfaces and experience continuous mild vibrations, which leads to fatigue corrosion. It does not occur on a surface in continuous motion. In a car moving normally, this type of corrosion does not occur because the relative motion between the bearing surfaces (rotation) is very large. The cause of abrasive vibration corrosion is that the abrasive vibration effect destroys the metal protective film, causing the exposed metal to oxidize rapidly; wear and oxidation occur repeatedly, thereby exacerbating the damage. Furthermore, the metal surface undergoes cold welding or melting due to compression; subsequently, as a result of relative movement, metal particles break off and oxidize rapidly. Both produce oxidative rust particles that damage the metal interface. Oxygen is important in fretting corrosion, but there are also some types of fretting corrosion that do not require oxygen. Protection methods include applying lubricating grease to the contact surface, which reduces friction and eliminates oxygen; it is even more effective if the surface is phosphated as well. Cemented carbide can also be used, along with shot peening or cold working, to increase surface hardness, etc.