There are reasons why the study of is very important to modern structures. Some of the primary reasons are; safety, economics, and conversation. In the past, has done lots of damages that could be expected from it. It had contributed to the premature failure of bridges or structures due to negligence leading human injuries and loss of life.
Research has shown that some of the industrial equipment operational failures could be attributed to unnoticed taking place on the vital parts of equipment. While other factors could contribute to the mechanical failures of equipment, serves as the hidden source for some of them.
Some years back, the National Institute of standards and Technology (formerly the National Bureau of Standards) estimated that the annual cost of in the United States was in the range of $9 billion $90 billion. A figure later confirmed by other organizations including the National Association of Engineers.
Some of the corrosions included in the estimate are; corrosion from chemical processes, corrosion of highways and bridges from deicing chemicals, corrosion of steel fences, atmospheric of various outdoor structures such as buildings, bridges, towers, automobiles, and ships and other structures exposed to the atmospheric environment.
From overall records of corrosion-protection approach, it had been found that the cost of protection against atmospheric is approximately 50 percent of the total cost of all protection methods.
By definition, is the degradation of a material’s properties or mass over time due to environmental effects. The tendency of materials’ compositional elements to return to their most thermodynamically stable state gives rise to gradual degradation known as .
The degradation process for metallic materials means the formation of oxides or sulfides, or other basic metallic generally considered as ores. Meanwhile, only inert atmospheres and vacuums can be considered free of for most metallic materials.
In the absence of means of protection, iron, and steel corrode in the presence of both oxygen and water. If either of these materials is absent, may not take place. Experiments have revealed that rapid may take place in water and the rate of the is proportional to the following; acidity or velocity of the water, the motion of the metal, increase in the or aeration, the presence of certain bacteria, or other less prevalent factors. However, the process can be retarded using the application of protective layers and films.
The high alkalinity of water also reduces the rate of on steel surfaces. The amount of is controlled by either water or oxygen which are essential for the process to take place. For instance, steel will not corrode in dry air and is negligible when the relative humidity of the air is below 30% at normal or reduced temperatures. The prevention of by dehumidification is based on this.
The fact is that all structural metals corrode to some degree in natural environments. However, bronzes, zinc, brasses, stainless steels, and aluminum corrode so slowly under the condition in which they are placed that they are expected to survive for long periods of time without protection.
Corrosions such as these, follow the basic laws of thermodynamics. It is an electrochemical process such that under controlled conditions it can be measured, repeated, and predicted. Since it is governed by reactions on an atomic level, processes can act on isolated regions, uniform surface areas, or result in subsurface microscopic damage.
Originally posted 2018-10-22 11:02:23.
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