One of the most common materials used in industry and construction is metal. Even with the advent of technological fiberglass and composites, its unique combinations of operational properties do not lose relevance. Nevertheless, factors such as aging of the metal, the effect of fatigue, corrosion, and other fracture processes limit its application, forcing technologists to seek means to increase the structure's durability.
Aging process
Under the aging of metal alloys and pure elements refers to a change in their performance. Over time, designs and parts change in their structure, which is reflected in performance. It is believed that the aging process of the metal has negative consequences, although it also determines the increase in certain useful technical and physical properties. For example, the hardness of the material increases, although brittleness also increases. In any case, a change in structure rejects the performance that is being calculated, for example, when developing a project for a building or machinery.
Time is the main cause of aging, but not the only one. A significant role in this process can play external conditions and especially chemical aggressive environments with which the material is in contact. Under normal operating conditions, there is a slow mechanical aging of the metal, against which the atoms of the product undergo diffusion.
Artificial aging
Since this process does not always lead to a complete loss of the operational value of the material, and also contributes to the buildup of some qualities, artificial aging is often used. For example, this technique is applied to aluminum and titanium alloys in order to increase their strength. This effect is achieved by heat treatment. If the natural aging of the metal can occur very slowly even at normal room temperature, then the artificial process requires special hardening. But it is important to consider the fundamental difference between this method and metal tempering technology. Aging under artificially created conditions leads to an increase in hardness and strength, but also contributes to a decrease in ductility.
Aging Prevention
In principle, this process cannot be stopped. But it is quite possible to slow it down or exclude factors that stimulate aging with a varying degree of success. For example, in some industries, metals of individual structures are periodically treated with protective solutions and polishes that minimize the influence of negative operating factors - chemical, temperature, mechanical, etc. As for slowing down the effect of metal aging under normal operating conditions, depending on the type structures or parts, the same heat treatment may be applied. Welders, for example, expose the seams to high temperature at 600-650 ° C. This technique is more closely related to the tempering of metals, but it also reduces the intensity of aging.
Chemical corrosion
The rusting process is more dangerous for metals in terms of changing technical and physical qualities. Corrosion can occur under the influence of chemical or electrochemical effects on the structure. And if the aging of the metal proceeds slowly, then the speed of the spread of rust can be very high depending on external conditions.
Chemical corrosion processes usually take place in cases where the metal is in direct contact with acid solutions, gaseous media, salts and alkalis. These are the most active corrosion stimulants that are always in the environment, but in different forms. Ultimately, a brittle and friable layer forms on the affected area, the presence of which reduces the durability of the material.
Electrical Corrosion
In this case, the process of spontaneous interaction of metal products with an electrolytic medium occurs. Against this background, the part undergoes oxidation, and the liquid active component is restored. Such processes can occur at contact points between alloys with different electrode charges. If salt or acid solutions are present in such areas, a galvanic pair is formed in which the element with a low electrode charge performs the function of the anode. Accordingly, the high potential makes the metal a cathode.
It is important to note that both aging and metal corrosion can occur even without strong stimulants. For electrochemical rusting, a minimal exposure to an acidic environment, which may be present in enclosed spaces, is sufficient. But most often such processes are subjected to the elemental base of cars. The reason for the occurrence of electrochemical corrosion in such situations may be blockage of carburetor jets, occurrence of fuel valves, irregularities in the wiring of electrical equipment pairs, etc.
Corrosion Control
Most remedies are external coatings, with which the destruction of the structure begins. For this, special spraying, paintwork, powders, enamels and varnish compositions can be used. An effective barrier against corrosion damage is also formed by methods of preliminary galvanizing before putting the structure or part into operation.
More serious training involves doping. Such a modification of the structure, in particular, can change the rate of aging of the metal, both upward and downward. There are also special high-tech methods used in industries and in industry. These include faeolithization, deaeration and thermal treatment.
Conclusion
The listed processes of destruction and changes in the structure of metals are only part of those phenomena that can affect the characteristics of the material. A special place among them is the effect of fatigue. This is a process in which gradually accumulated damage causes an increase in stress in the structure, which subsequently leads to the loss of operational properties. But unlike metal aging, its fatigue is almost always caused by external physical influences.
In order for none of the processes considered to have a negative impact on the structural resistance of the product, its susceptibility to the influence of certain factors should be initially evaluated. For this, technologists develop special methods for controlling the workpieces, indicating their weak and strong technical and physical qualities for the design materials.