We use metals on a daily basis in everything from our cars to the bridges we cross. However, corrosion presents one of the largest obstacles to preserving the longevity and integrity of metals. As a result of this natural process, metal corrodes and becomes weaker when it reacts with oxygen and moisture in the environment. Corrosion inhibitors are essential for maintaining the strength and aesthetic appeal of metal surfaces in order to counteract this.
When applied to metal surfaces, corrosion inhibitors are unique chemicals that greatly reduce or even completely stop the onset of corrosion. These inhibitors are available in different formulations and forms, each appropriate for a particular kind of metal and set of environmental parameters. From building to the automobile industry, knowing the different kinds of corrosion inhibitors and how to use them efficiently can save time, money, and resources.
Corrosion inhibitors come in a variety of forms, with distinct mechanisms of action for anodic, cathodic, and mixed inhibitors. While cathodic inhibitors slow down the reduction reactions, anodic inhibitors create a protective oxide layer on the metal surface. Combining the two characteristics, mixed inhibitors offer complete protection. The desired lifespan of the protection, the type of metal, and exposure circumstances all play a role in selecting the appropriate inhibitor.
In real-world applications, corrosion inhibitors are frequently added to paints and coatings to provide both protection and aesthetic enhancement. In order to increase the lifespan of machinery and equipment, they are also added to coolants, lubricants, and other industrial fluids. The cost and effort associated with metal degradation can be greatly decreased by incorporating corrosion inhibitors into routine maintenance procedures, guaranteeing that structures and components continue to be safe and dependable for extended periods of time.
| Types of inhibitors | Use |
| Organic inhibitors | Protect steel and iron from rust in water-based paints. |
| Inorganic inhibitors | Effective in high-temperature environments. |
Atmospheric corrosion protection
In order to shield metals from atmospheric corrosion, two types of inhibitors are utilized: contact type inhibitors and volatile inhibitors, which dissipate and move independently across the metal surface.
The following are high requirements for barrier materials when using volatile inhibitors:
- Materials should be impermeable for inhibitor vapors;
- The packaging should be airtight, otherwise the substance will immediately disappear.
Inhibitors can be used in a variety of ways to stop atmospheric corrosion in metal products:
- the inhibitor is applied to the surface of the metal from water solutions or organic solvents;
- The process of sublimation of inhibitors is carried out on a metal surface from the air in which there is a large concentration of inhibitor vapors;
- A polymer composition is applied to the metal surface, which includes an inhibitor;
- The product is wrapped in inhibited paper;
- A porous media with an inhibitor is directed into a closed space.
In the latter instance, the carriers are "Linopon" or "Linasil." These enclosed adsorbents preserve metals for an extended period of time and guard against corrosion and "bronze disease." Adsorbents also make it possible to preserve products in the event of a sudden change in the environment.
It is advised to use inhibitors for conservation purposes when the humidity is below the critical point and the air is clean. Acidic vapors are not permitted in the room where conservation is being done; these pairs are released during chemical cleaning.
With the development of a strong protective layer, inhibitor adsorption takes some time to happen. The length of time varies according to the inhibitor’s and the processed metal’s characteristics. Products made of metal are thoroughly cleaned of debris and fat before being processed inhibitory, followed by drying.
Note: Do not touch the metal with your bare hands prior to conservation. In the future, rubber gloves will be required for all work.
Protection for steel structures
The most widely used sodium nitrite aqueous solutions, particularly the viscous ones. This solution functions as a contact type inhibitor when applied to the product’s surface (heating systems or other metal structures, for example).
The efficiency of the substance is greatly increased by adding another ingredient (oxyethyl cellulose, glycerin, xylcer, or starch) to the aqueous solution of nitrite, which increases the viscosity of the structure. Specifically, the warranty metal protection period lengthens, independent of weather. Viscous substances prevent sodium nitrite solutions from drying out, prevent salt crystals from adhering to the metal surface, and lower the proportion of substance that sprays when humidity is high.
The most popular solutions to protect cast iron parts are 25% sodium nitrite solution for steel products and 40% solution for other products. A solution that has been heated to 65–85 degrees is used to process the metal. A concentrated inhibitory solution is created when sodium nitrite crystals form on the surface as a result of moisture condensation during storage (for instance, when stored in between technological operations).
The metal passively adopts this solution. To counteract the acidic atmospheric components that come into contact with the condensing moisture, a small amount of soda (up to 0.6%) is added to the nitrite solution. Remember that local corrosion occurs when the concentration of sodium nitrite is lowered to levels below the designated threshold. This factor explains why viscous solutions can be used appropriately for long-term storage.
Nitrite is the volatile inhibitor that is most frequently used with diciscilaxylamine. This material works wonders for cast iron and steel, but it exacerbates the corrosion processes in copper and its alloys, magnesium, cadmium, zinc, tin, and lead alloys. Flying protective materials have no effect on the mechanical properties of plastic, skin, rubber, paints, or varnishes, nor do they alter the resistance of aluminum, nickel, or chromium to corrosion.
Alcohol solutions are used as a form of this inhibitor. There are 1.5–2.5 grams of substance per square meter, and an 8.5% alcohol solution is used. The part is either sealed or kept in a separate area as soon as it is processed.
Protection of copper and its alloys, as well as silver
Benzotriazole, a contact type inhibitor, is used to stop corrosion processes on copper and its alloys as well as on silver. When this material comes into contact with 1 and 2-band copper salts, it forms polymer compounds that are resistant to high temperatures and insoluble in water.
Benzotriazole inhibits the so-called "bronze disease" because insoluble structures are present. Benzotriazole is advised for the protection of both purified objects and those where the decision is made to maintain the original patin or corrosion layer. Moreover, benzotriazole retards the darkening of copper, silver, and bronze items.
Objects are cleaned of fat and mud and then submerged in a 3% benzotriazole solution. You must keep the temperature at least 20 degrees in this situation. The solution needs to be heated to fifty degrees in order to process large objects. After that, a damp h/b cloth is used to wipe and dry the metal.
Be aware that benzotriazole is a substance that causes cancer. As a result, you must prevent the solution from getting directly on your skin. You must wear safety goggles, an apron, and protective gloves when working.
Sulfur is found in the captax. Metals become much more resistant to corrosion after being processed by captors into copper and bronze products. If the solution is between 70 and 80 degrees, 30 minutes of immersion will yield the best results. When compared to benzotriazole, kaptax can have a stronger effect in certain situations.
Chromates are one class of inorganic inhibitors to be aware of. One of the least expensive ways to prevent copper, its alloys, and silver from darkening is through passivation using chromatics. Either a cathode current or no current is used during the passivation process. The protective properties of the formed films are unaffected by large variations in the electrolyte components and surface processing regime used during chromatting. Metals are stored in a chrome acid solution (1 gram per liter) for a few minutes. The developing film is highly resistant to the effects of hydrogen sulfide and salt solutions, as well as humidity.
Products made of silver are pasivated using an overlap in cathode current. In addition, up to 40 grams of potassium carbonate, 20 grams of caustic soda, and 40 grams of sodium brahromate make up the electrolyte. The amounts are divided into one liter of liquid. The exposure duration is 60 seconds, and the current density is 0.1 ampere per square centimeter. The solution is kept at room temperature.
One can successfully passivate silver even with a standard dip in sodium brahromate or chrome anhydride. But it’s important to make sure the solutions don’t contain any unnecessary acids. Double processing yields better results: first using a cathode method, and then dipping in a sodium orphan tonsillitis solution.
Be aware that chromium anhydride and sodium brohromate can harm your skin and respiratory system. As a result, you must handle these materials in a room with adequate ventilation, rubber gloves, and a respirator.
Metal corrosion inhibitors are crucial tools for extending the life and preserving the integrity of various structures and components by shielding metal surfaces from the damaging effects of rust and corrosion. These inhibitors function by creating a shield that keeps corrosive substances and moisture from getting to the metal surface. Inhibitors come in a variety of forms, both inorganic and organic, and they are appropriate for use in various settings. Industries can dramatically lower maintenance costs and improve the longevity of their metal assets by knowing and using the right inhibitor.
Protection when washing
Water washing can cause corrosion processes in the vicinity of the cleaned surface, particularly when cleaning steel or cast iron. At the same time, water rigidity is greatly influenced by how aggressively corrosion occurs. The degree of water’s influence on the emergence of corrosion processes increases with its softness.
The amount of sulfates and chlorides in it also contributes to the activity of corrosion, in addition to salts. In naturally occurring water, their concentration can range from 50 to 5000 mg/liter.
The following water aggression classification is applied:
- A slightly aggressive environment – the concentration of sulfates and chlorides of less than 50 milligrams per liter;
- The average aggressive environment is the concentration of sulfates and chlorides from 50 to 150 milligrams per liter;
- Highly aggressive environment – the concentration of sulfates and chlorides over 150 milligrams per liter.
The following concentrations of salted water are permissible to use, per GOST:
- sulfates – up to 500 milligrams per liter;
- chlorides – up to 350 milligrams per liter.
Hydrazine is one of the reconstitutes used to lessen oxidation during washing. Aquarists connect oxygen to water. The interaction between oxygen and hydrazine removes nitrogen from the aquatic environment without causing any issues or endangering the formation of corrosion.
One gram per liter is the permissible inhibitor level. The process of boiling removes most of the oxygen from the water.
Maintaining the longevity and integrity of metal surfaces requires an understanding of the different types and applications of metal corrosion inhibitors. Significant damage, monetary losses, and safety risks can result from corrosion. The damaging effects of corrosion can be avoided on metals by using the appropriate inhibitors.
In order to stop corrosive substances from getting to the metal itself, corrosion inhibitors function by covering the metal in a layer of protection. Anodic, cathodic, and mixed inhibitors are among the various types of inhibitors; each has a particular purpose based on the environment and the kind of metal that needs to be protected. These factors need to be carefully considered when selecting the right inhibitor.
By effectively extending the lifespan of metal structures and components, corrosion inhibitors improve safety while lowering maintenance costs. The correct inhibitor can make a big difference in a variety of situations, including household projects, automotive maintenance, and industrial applications. To get the best results, always make sure to apply the inhibitors correctly and according to the manufacturer’s instructions.
In conclusion, metal corrosion inhibitors are an effective weapon against the deterioration of metals. You can protect your metal assets and guarantee their longevity for years to come by making educated decisions based on your understanding of their types and applications. Choose the inhibitor that best meets your needs while keeping in mind the unique requirements of your project.
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