Ways to reduce the intensity and corrosion rate of metal products

Products made of metal are necessary in many industries, including the building and automotive industries. Nonetheless, corrosion is one of the main issues these industries deal with. Metal can corrode over time due to exposure to chemicals, moisture, and environmental factors, weakening its structure and reducing its lifespan. Fortunately, there are a number of practical methods for lowering the severity and rate of corrosion, guaranteeing the continued dependability and durability of metal products.

Applying protective coatings is one of the most popular ways to prevent metal from corroding. By acting as a barrier, these coatings stop corrosive substances from getting to the metal surface. For example, paints are commonly used due to their ease of application and adaptability to various environmental conditions. Inhibitors found in specialized anti-corrosive paints neutralize corrosive agents and add another layer of defense.

The application of galvanization is another successful strategy. Zinc serves as a sacrificial metal in this process, and it is applied on top of the metal. Zinc shields the base metal from corrosion because it corrodes more readily than the underlying metal. In outdoor structures and environments with high exposure to chemicals and moisture, galvanized metal is frequently utilized.

Effective design and routine maintenance are also essential for minimizing corrosion. It is possible to detect and treat early indications of corrosion before they worsen by making sure that metal products are routinely inspected and maintained. Furthermore, metal structures last a lot longer when they are designed with corrosion prevention in mind, such as by avoiding crevices where moisture can collect.

Protective coatings, galvanization, and proactive maintenance are three strategies that industries can use to successfully lower the intensity and rate of corrosion in metal products. In the long run, this not only increases the products’ lifespan but also lowers costs and improves safety.

Classification of species of rust

Signs of corrosion are categorized as follows:

1. In terms of uniformity. More uniform, superficial corrosion (at which the thickness of the product walls decreases the same degree) and uneven, focal corrosion, which is characterized by the occurrence of damaged points or ulcers on a steel surface.
2. By the orientation of the action. Electoral corrosion is found, in which only certain components of the metal structures are affected, and contact, destroying a certain metal (for bimetallic compounds).
3. In terms of its action, such types of corrosion as intercrystalline, destructively acting along the boundaries of steel grains (with gradual spread deep into), and voluminous, affecting the entire surface at the same time are known.

If the metal’s contact surface is additionally impacted by stretching stresses, an environment that is chemically aggressive, and unfavorable temperature and humidity fluctuations, the intensity of the corrosion increases dramatically.

Because of the cracking between neighboring crystallitis and their blocks, the intensity of the corrosion increases several times. Steel is even more aggressively affected by external stretching stresses.

Mechanisms of the emergence and development of corrosion phenomena

Since most steel surfaces are exposed to water, aqueous solutions of salts, acids, and alkalis, and environments with a certain degree of humidity, the most common mechanism for rust formation is electrolysis. The only exception is furnace corrosion, which happens in heating device metal structures and causes surface destruction as a result of high-temperature rust scale formation.

Electrolytic

The hydrate of iron oxide Fe (OH) 2 is the end result of steel iron hydration through electrolytic corrosion in the presence of oxygen. We refer to this phenomenon as anode-type corrosion. However, the procedure doesn’t stop there. The iron oxide hydrate is an unstable material that rapidly breaks down into different iron oxides when exposed to water or water vapor.

• At elevated temperatures, the FEO iron is formed mainly;
• with indoor or slightly higher – iron oxide Fe2O3;
• at intermediate (in the temperature range +250 … +450 ° C)-magnetic oxide-oxy iron FE3O4.

Regardless, when steel rusts, the only colors that can indicate this phenomenon are reddish-brown or grayish-yellow.

In the presence of acids

The process by which rust forms in the presence of acids, acidic solutions, or oxygen-free liquid media is slightly different. Here, the formation of hydrides—iron compounds combined with hydrogen—causes an anode dissolution of steel. However, the latter are chemically unstable materials that oxidize quickly in humid environments and form rust of a different kind, albeit more loose. Iron hydrides decompose more quickly in environments or the atmosphere that contain sulfur compounds.

In the presence of loads

The third scheme states that corrosion happens when there are outside loads on the contact surfaces. Here, lubrication is a necessary third component in addition to the two conventional ones. Since oxygen and hydrogen are always present in organic compounds, mechanochemical oxidation reactions of lubrication start to flow when the temperature of the compound increases. They conclude with the fact that a used and partially degraded lubricant starts to actively oxidize the surfaces, forming rust, rather than lowering friction.

Methods for assessing corrosion processes

The type of corrosion phenomenon determines the degree of corrosion in relation to steel. usually start with rust on the surface being visually detected.

You can fairly accurately assess the extent of surface damage and the strength of corrosion processes using a standard microscope or even magnifier.

The degree of damage is more precisely determined by the so-called corrosion indicators. With their assistance, you can learn:

• loss of the mass of the product due to corrosion;
• reduction of the linear size of the part or design;
• The intensity of damage depending on the time of stay of the part in the corrosion-active environment.

There is a qualitative evaluation of the rust’s presence in addition to a quantitative one. Its indicators are variations in the steel’s microstructure. They thus recognize electoral corrosion or inter-qurystalline corrosion. Much less frequently, the amount of hydrogen released or the shift in the medium metal’s chemical composition control the intensity and rate of corrosion.

The following specific corrosion indicators have an impact on the corrosion rate:

1. Integral corrosion characteristic. It is calculated as the loss of a mass of steel product in a year, divided into a surface area on which rust appeared. At the same time, the steel surface underlying the surface is considered one on which there are even single damaged points.
2. Linear corrosion. Calculated depending on the density of the part and thickness of the layer of the product that corroded over the year.

Which value should be used instead? An integrated evaluation of corrosion processes is preferred if the part can be precisely weighed before and after it operates, or if it can be used to assess changes in the chemical composition of the solution in which the part operated. They assess the effectiveness of contact lubrication in particular. It is better to use the second parameter if the part is only checked a few times a year or if an evaluation of the severity of corrosion phenomena needs to be done right away.

Determining the speed of corrosion processes

Corrosion indicators aid in assessing how severe unfavorable changes are. Use the idea of "metal corrosion" to accomplish this. It can be assessed using two distinct attributes that are subject to change over time.

The following quantitative traits can be used to install corrosion indicators:

• on the area of ​​the corroded surface;
• by total loss of mass;
• by changes in density;
• by the time spent by the part or structure in the corrosion environment (day);
• to reduce thickness.

Simultaneously, the following numerical standards could be used to evaluate the type of steel corrosion over a given duration:

• Absolute corrosion losses in area;
• change in linear dimensions of the product;
• linear corrosion resistance;
• corrosion rate;
• linear corrosion rate (millimeters per year);
• total corrosion resistance or durability.

In actuality, the technique used to protect the metal surface determines which criterion is used. It can be coated in protective coatings or painted with atmospheric paints. An evaluation of protection effectiveness can be made more precisely if corrosion progresses uniformly.

If the product’s rust formation varies in intensity across different areas, you should only select the best protection strategy when the part is subjected to external stretching stresses. Subsequently, as time passes, the surface’s appearance and certain physical properties—namely, electrical resistance and thermal conductivity—also alter.

Corrosion testing of metals

Climate variables such as temperature, the make-up and relative humidity of the surrounding air, and the way external loads are distributed are examples of corrosion indicators. It is also essential to consider the amount of precipitation, potential air pollution, and how the lighting changes throughout the day. For instance, corrosion processes are sharply triggered in areas of flue waste emissions close to chemical plants and metallurgical production, where there is also a sharp rise in the percentage of SO2.

Quantitative corrosion on time dependences can be used as markers of corrosion activity:

1. Linear – most often this is characteristic of metal surfaces that do not have a protective coating.
2. Exponentially decreasing – occur with acid corrosion of conventional metals and alloys.
3. Exponentially increasing – when there is a protective coating on the surface of the part.

Under these circumstances, the intensity of rust formation decreases:

• small wind speed;
• reduced cyclicity in time of changes in the indicators of relative humidity;
• The nature of the effect of the corrosion-active medium on the surface.

There are no conditions for mixing the flow that washes the steel’s contact surface when the wind is weak or nonexistent. Throughout the year, there are extended periods of both high and low humidity, which allows the surface rust film to form, swell, and separate from the base metal. Although the surface thickness will decrease, the corrosion processes must "start" first, which takes time and appropriate conditions (wind or occasionally changes in the chemical composition of the air).

Steel can absorb moisture, acid, or alkali in the form of drips or jerky. The first approach is typical of regions that see higher levels of precipitation, while the second is appropriate for situations where a metal structure or part operates in an unfavorable environment.

For metal products to remain functional and last longer, their intensity and rate of corrosion must be reduced. The use of superior protective coatings is one practical strategy. By acting as a barrier, these coatings keep corrosive materials and moisture from getting to the metal surface. The protective properties of these coatings can be greatly improved by timely reapplication and routine maintenance.

One more crucial tactic is to apply corrosion inhibitors. These chemicals slow down the corrosion process when they are applied directly to the metal or added to the surrounding environment. Particularly helpful in industrial settings where metals are subjected to challenging conditions are corrosion inhibitors. To add an additional layer of protection, they can be mixed into paints or applied separately.

Corrosion mitigation also heavily depends on the choice of materials. Selecting metals and alloys with inherent corrosion resistance can help you avoid needing constant upkeep and repairs. For example, alloys made of aluminum and stainless steel are well-liked because they naturally resist corrosion.

Controlling the environment is another useful strategy. Corrosion rate can be reduced by limiting exposure to corrosive substances like chemicals, saltwater, and harsh weather. This can be accomplished by handling metal products with care, using dehumidifiers, and managing the surrounding environment.

Protective coatings, corrosion inhibitors, careful material selection, and environmental control all work together to provide a comprehensive approach to corrosion reduction. By putting these tactics into practice, metal products’ performance and durability can be greatly enhanced, which will eventually result in lower costs and more dependability.

One of the most effective ways to reduce the intensity and rate of corrosion of metal products is to apply protective coatings, like paints and sealants, which serve as barriers against chemicals and moisture. Early detection of corrosion through routine maintenance and inspection enables prompt repairs. Furthermore, metal structures can have a much longer lifespan when corrosion-resistant materials, such as stainless steel or galvanized metal, are used, and appropriate design principles are used to reduce the amount of dirt and water accumulation. By using these techniques, metal products’ integrity is maintained and long-term replacement and repair costs are reduced.

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