What is a corrosion inhibitor?

Where and how are metal corrosion inhibitors used?

Statistics say that every year a quarter of the world's metal is exposed to corrosion. For this reason, a lot of money is spent on repairing metal products, communications and other equipment. It is often more cost-effective to completely replace a rusted product than to attempt to repair it.

However, there is a substance that slows down the destruction process - a metal corrosion inhibitor. When answering the question of what corrosion inhibitors are, it is necessary to find out the requirements for them, their types, mechanism of action and application.

Concept and requirements

A corrosion inhibitor is a substance that, in a certain concentration, can suspend or stop the rusting process of parts. The retarder may contain one or several elements that form a whole compound.

The effectiveness of the action depends on two indicators:

1. metal destruction inhibition coefficient;
2. degree of protection during anti-corrosion treatment.

The main requirements for all inhibitors are:

• instantaneous action;
• price and raw material availability;
• resistance to oxidation;
• Stability of action when exposed to temperatures; Effectiveness of action with minimal concentration on the surface of structures.

Types of rust inhibitors

Depending on the type of environment they are divided into:

1. acidic;
2. oil;
3. atmospheric;
4. neutral.

1. The first type of inhibitors is used in acidic environments in small concentrations. As a rule, no more than 5 grams per 1 liter. The essential and active elements of the substance are nitrogen, sulfur, and oxygen, which are used in etching.

A prime example is pickling, which removes scale from steel. The disadvantage of such substances is that the metal loses 5% of its properties when exposed to them.

2. Petroleum environment inhibitors are actively used in oil production. Since oil contains impurities and hydrogen sulfide, it is also a highly corrosive environment. To reduce the aggressiveness of the oil environment, anti-ignition agents and a paraffin-forming mixture are added to it. The product itself, which interacts with oil, is coated with amine-based inhibitors, as well as substances that form a film on it with a water-repellent effect.

3. Atmospheric corrosion inhibitors are divided into:

Volatile agents are salts of organic or inorganic acids, the concentration of which increases near the surface of the part, thereby protecting it. Volatile moderators include benzoates, nitrobenzoates, phosphates, nitrites and others. There are special requirements for the packaging in which they are contained. It must be sealed and impenetrable.

Contact inhibitors are applied to the metal itself, as a result of which a film is formed on it that does not allow moisture to pass through. This type of moderator is not characterized by high evaporation from the surface. Most often, the base used is benzotriazole, which is a carcinogenic substance and requires special care when working with it. Chromates and sulfur-containing captax are also used. These substances are used to process copper, bronze, and silver.

4. Neutral environment inhibitors are divided into three types of agents:

• forming poorly soluble compounds (borates, sodium carbonate, phosphates, silicates);
• with oxidative effects (sodium chromates and nitrite);
• with weak oxidation (for example, tungstates).

Mechanisms of action of rust inhibitors

The substances themselves do not come into contact with the environment. They interact directly with the metal surface.

There are two ways of interaction of an inhibitor with a metal surface:

• adsorption method;
• film formation method.

During adsorption, the volatile substance is concentrated at the surface of the metal and creates a protective environment. Film formation occurs during contact application of the product to the surface of the part. As a result, a water-repellent layer appears on it, preventing the formation of rust.

At the electrochemical level, inhibitors act on the material through three processes.

1. The first process is anodic inhibition. Oxidizing agents such as nitrates, molybdates, silicates, phosphates, and sodium benzoate act as moderators.

Anodic inhibition is effective if oxygen is used in addition to these compounds. It accumulates in significant concentration near the surface of the metal, and the compounds form a protective film. It is necessary that the concentration of anodic substances is not too low. Otherwise, the reverse process may occur, accelerating the destruction of metal structures.

2. The second process is cathodic inhibition. It is less effective than the action of anodic substances. Cathode retarders are able to slow down the rusting process by creating insoluble areas of calcium carbonate compounds on the surface of products. This compound is formed in an alkaline environment. To do this, the part is placed in alkali.

Under its influence, calcium carbonate precipitates and forms a protective insoluble layer. Cathode inhibitors, like anodic inhibitors, are ineffective in an acidic environment.

3. The third process is mixed. The most effective and uniform way to protect metal from corrosion, combining the action of both anodic and cathodic substances. Retarders of the mixed process can be polyphosphates, as well as silicates and chromates.

Where and how are rust inhibitors used?

In general, the use of metal corrosion inhibitors is associated with metallurgy, the oil industry, as well as in the production and repair of equipment. For example, for products made of bronze, silver and copper.

1. Commonly used is Benzotriazole. This contact agent effectively acts on copper and silver products, forming a protective layer that is poorly soluble in water and stable at high temperatures.

Benzotriazole is effective for removing dark stains on copper, silver and bronze items. Typically a 3% benzotriazole solution heated to 50°C is used.

The anti-corrosion treatment process will be more effective if the specified temperature is maintained for 20 minutes. The part, previously cleaned of dirt, is placed in the solution. After cleaning, it must be wiped with a cloth.

Do not forget that benzotriazole is dangerous for the skin. It is necessary to carry out the work wearing special gloves and glasses.

2. Of the inorganic inhibitors, chromates are most often used. This is one of the most accessible drugs to use. The treatment of copper and silver with chromates can be carried out using cathodic current. Or without his participation. In this case, the metal is placed in chromic acid for a couple of minutes. As a result, a waterproof film appears on its surface.

3. Silver is often processed using cathodic current. In this case, an electrolyte is taken containing caustic soda, sodium bichromate and potassium carbonate, distributed per 1 liter of liquid. The resulting solution should be at room temperature. The product is placed in it, and a current with a density of 0.1 ampere per 1 cm2 is passed through the solution for 1 minute.

Silver items can simply be dipped into a sodium bichromate solution. It is important that there are no impurities in the solution. The most effective will be a combination of two processing methods: first treatment with cathodic current, and then dipping the part into a solution of sodium bichromate.

4. Captax has also proven itself in use.

In some cases, it turns out to be more effective than Benzotriazole. This inhibitor contains sulfur. It is enough to immerse copper or bronze in a Captax solution heated to 800C for 30 minutes. This will increase the resistance of the metal product to corrosion.

(1 5,00 out of 5)

Source: https://plavitmetall.ru/obrabotka/ingibitor-korrozii-metalla.html

What you need to know about metal corrosion inhibitors?

The substance-composition, complex in its structure, is [corrosion inhibitor], capable of stopping metal corrosion.

It is mainly used as an additional component of the composition to create a durable coating.

This composition inhibits the processes of changing the electrochemical characteristics of metal objects.

It is used at oil refineries, machine-building factories, and is used in metallurgy.

This composition is necessary for water supply and heating systems, for industrial oils and lubricants.

Corrosion inhibitor class

The composition of metal rust protection is included in a certain class of inhibitors depending on:

• the nature of the reaction to metal: adsorption and passivating substances;
• environmental conditions in which the metal is located: compositions for protecting metal parts from corrosive damage in places with high acidity, as well as in a neutral and hydrogen sulfide atmosphere;
• chemical composition: volatile corrosion inhibitors, organic or inorganic additives to protect the metal;
• features of rust protection: anodic, cathodic, as well as combined chemical compositions.

An agent that slows down the corrosion process acts by changing the state of the metal shell. This occurs due to the formation of a complexly soluble compound or the adsorption of a corrosive composition.

The inhibitor affects the metal in two ways. It can transform the rust formation activity or reduce the size of the area exposed to corrosion.

The resulting layer of inhibitors is thinner than the applied general coating. For example, a class of inhibitors such as passivators for metal tends to envelop its surface with a specific film.

This film reduces the risk of corrosion to a minimum. Passivating components are chromates and nitrates that resist rust formation.

The adsorption substance is absorbed by the outer layer of the metal, which is why a thin film appears, distinguished by special characteristics.

It slows down and sometimes completely prevents corrosion. This dense film covers the metal as a result of its treatment with organic chemistry or PVA.

IMPORTANT TO KNOW: How to phosphate metal at home?

Organic-based composition and inorganic mixtures

Organic-based composition does not absorb products that may rust. The organic matter remains in the top layer of the metallic material, inhibiting the formation of corrosion.

Therefore, it is used by acid etching of rust stains on metal structures of heating systems.

The components included in the organic composition provide a 100% anti-corrosion result. These include aromatic and aliphatic substances.

The composition of corrosion inhibitors of this group includes atoms of sulfur, nitrogen, and oxygen.

The substance of organic acids and salts contains hydroxyl and aminoxyl compounds. They perfectly protect elements of systems where the environment is saturated with acids, oils or electrolytes from rust.

Thiols and sulfides protect metal structures of systems at a high level. This group includes benzotriazole and other aliphatic organic compounds.

Inhibitors that are affordable are amines. They protect the metal in the acidic or aqueous environment of heating systems, negating the reaction of the anodes or cathodes. But their effectiveness is lower than that of thiols.

The structure of inorganic compounds contains anions PO, NO, SiO, as well as cations of calcium, arsenic, and bismuth.

Anode inhibitors, whose nature is inorganic, create a protective shell on the metal surface. The film is very thin, only 0.01 mm. But its density prevents iron from turning into solution.

The film created by phosphates protects metal and steel communications of water drainage systems from corrosive damage.

Cathode inhibitors can form a composition on microcathodes that does not undergo dissolution. This substance creates a protective insulating layer.

Currently, the most well-known cathodic inhibitor is calcium bicarbonate. It forms a shield against electrolytes. The production of this substance does not require much money, so it is inexpensive.

IMPORTANT TO KNOW: Metal cadmium plating technology at home

Dodigen 4482 and M-1 inhibitor

An inhibitor for protecting metal in an acidic environment is dodigen 4482. It is used as a protective agent for gas and oil systems.

This inhibitor is needed when metal structures need to be protected from the dangers of heavy loads, the influence of an acidic atmosphere or heavy use.

The film of dodigen 4482, whose density is very high, creates a good barrier against the attack of carbon dioxide and hydrogen sulfide. This connection is economical and effective in use.

It is very simple to apply it to the surface, and the metal will not be in danger of rusting, since the degree of protection is quite high.

The M-1 inhibitor class is required in order to protect the metal from corrosion at the microbiological and atmospheric level in different climates.

It is needed for reliable preservation and safety of devices in the thermal power industry, that is, for heating systems or other areas of production.

Direct impact on metal surface

This method of protecting metal from danger that threatens it requires the use of various coatings. It can be paint, rubber or metal and is applied by spraying or gumming.

Gumming is the process of protecting equipment with a rubber coating, which is often done during chlorine production.

Manufacturers note that rubber film is characterized by excellent resistance to chemical attack, protecting containers, bathtubs and other chemical equipment from the negative influence of an aggressive environment.

The gumming procedure can be both cold and hot, which is carried out by vulcanization of epoxy and fluoroplastic compounds.

It's not just about choosing the right inhibitor, but also about its correct application. Usually the instructions on this matter contain quite detailed information from the manufacturers.

The galvanic deposition method is very common, and the rapid sputtering method is even more common. It facilitates a large number of tasks.

To obtain a reliable coating that has a number of protective properties, it can be applied to metal and powdered material.

IMPORTANT TO KNOW: Technology for stamping sheet metal parts

How to protect chemical equipment from corrosive effects?

Any metal equipment is at risk of rust stains. It is important to protect all elements of heating systems from rust.

But first they select a high-quality coating, look at the properties of the environment and its aggressiveness coefficient, evaluate the operating conditions and temperature conditions.

Sometimes it can be difficult to choose the appropriate coating class for equipment in a neutral environment, since there is one unfavorable indicator that makes you think long and hard.

A difficult situation can arise when steaming a propane tank, even if it is done rarely, once every two months.

It must be remembered that the protective film must be resistant to a specific reagent.

Experts do not recommend comparing gas-thermal spraying methods with each other. You should not think that the class of one of them will be of higher quality, because each such method is characterized by its pros and cons.

As a result, the resulting film has a density and properties that are different from other coatings, and solves the problems in its own way.

When choosing a composition, after application of which a barrier film will appear, and the method of its distribution on the surface, one must proceed from the specific problem. In the chemical industry, spraying is usually used for routine repairs.

To prevent metal equipment from being in danger of rusting, its surface is prepared for treatment before using an acid corrosion inhibitor.

This is the only way the coating will produce the desired effect. The application of paint and varnish material is always preceded by blasting the surface. It guarantees the creation of a base for paint with roughness.

You can see more and more modern materials on the construction market. Therefore, choosing a means to protect metal structures from their main danger is not easy to make.

But chemists now face another problem: to decide what is more expedient and economical - to protect equipment elements in a timely manner or to completely replace them.

Source: https://rezhemmetall.ru/ingibitor-korrozii-metalla.html

Corrosion inhibitor

• Metal inhibitors
• Compound
• Properties
• Protection
• Application

Translated from Latin, inhibitors are translated as delay. It has found wide application in modern industry.

Metal corrosion inhibitors

The inhibitor is not a specific substance. This is the name given to a group of substances that are aimed at stopping or delaying the occurrence of any physical or physico-chemical processes. For the most part, it is aimed at delaying enzymatic processes.

Inhibitors mainly act in cases where there is a chain reaction or processes with active centers and particles. The inhibitor acts on the active substances. He either blocks them or delays them. In some cases, it reacts with active particles and due to this, free radicals are formed.

Important: The inhibitor should be introduced into the reaction system of two substances in a small amount. It should not exceed the volume of elements between which there should be a reaction.

Composition of corrosion inhibitors

Inhibitors are represented by the following substances:

• Hydroquinone. This inhibitor belongs to the category of oxidation inhibitor.
• Technetium compounds. This inhibitor serves to delay the formation of corrosion on steel materials.
• Nitrogen trichloride. It is used in the reaction of chlorine with hydrogen.

Attention: When reacting chlorine with hydrogen, this inhibitor should be administered in a minimal amount. One thousandth of the total volume of reagents will be enough to stop the interaction process.

Inhibitors can act by two different principles on the interaction of two substances:

• Reversible. At the same time, the inhibitor molecules do not change the molecules of substances that react with each other.
• Irreversible. As a result of this action of the inhibitor, the molecular composition of one of the reacting substances is affected.

Table 1. Physico-chemical properties of corrosion inhibitors

No. Inhibitor brand General characteristics Density at 20 °C, g/cm3, % Viscosity at 50 °C, cSt Temperature, °Pine nitrogen, within resins, no more than mechanical impurities, hardening, auto-ignition flash

1	I-1-A* (TU 38-103246-87)	Viscous dark brown liquid with a characteristic odor of pyridines, almost insoluble in water, soluble in organic solvents, as well as in hydrochloric, sulfuric and other strong acids	1,01,1	7,09, 5	5	0,2	—	—	—	—
2	I-1-V* (TU 38-103-238-74)	Dark brown liquid with a characteristic faint odor, easily soluble in acids and water	1,251,35	—	3,0	—	—	—	—	—
3	"Sever-1" (I-2-A)* (TU 38-103-201-76)	Easily mobile dark brown liquid, soluble in benzene, alcohol, acetone, hydrochloric and sulfuric acids	0,931,05	4,906,65	3,5	0,2	712	-65	+23	+385
4	I-Z-A* (TU 38-403-29-73)	Dark brown liquid with a characteristic odor, highly soluble in polar organic solvents and mineral acids	0,991,07	8,311,0	3,5	0,2	15	-33-45	6	+413
5	I-4-A* (TU 38-403-44-73)	Dark brown liquid with a characteristic odor, highly soluble in benzene, alcohol, acetone, hydrochloric, sulfuric acids and a number of other products	0,941,00	4,96,65	3,5	0,2	37	-50-75	+15	+413
6	I-4-D (TU 38-403-46-73)	Dark brown viscous liquid with a characteristic odor, emulsifies in aqueous solutions, dissolves in toluene, chloroform, carbon tetrachloride and some other media	0,850,95	—	—	—	6595	-12-15	+81	+239
7	"Taiga-1" (I-5-DNA) (TU 38-403-47-73)	A highly mobile dark brown liquid with a characteristic odor, emulsifies in aqueous solutions, dissolves in hydrocarbons	0,920,96	—	—	—	—	-50	+20	+340
8	I-2-E	Easily mobile dark brown liquid with a weak characteristic odor, soluble in water, alcohol, acids	1,01,1	—	—	810	—	-50	—	—
9	"Taiga-2" (I-5-DTM) TU 38-403-78-78)	Highly mobile dark brown liquid, soluble in alcohol, benzene, dichloroethane and other organic solvents	0,870,89	—	—	3,9 4,0	—	-45	—	—
10	I-21-D (TU 38-403-101-78)	Highly mobile dark brown liquid, soluble in alcohol, benzene, dichloroethane and other organic solvents	0,80,9	—	—	5,0	—	-16	—	—
11	I-30-D (TU 38-403-79-76)	Easily mobile dark brown liquid, emulsifies in water, dissolves in alcohol, benzene, dichloroethane	0,85 0,87	—	—	5,0	—	-40	—	—
12	I-K-10 (TU 38-403-68-75)	Easily mobile brown liquid, soluble in water, alcohol, acids	1,061,1	—	—	811	—	-50	—	—
13	I-K-40 (TU 38-403-75-75)	Easily mobile brown liquid, soluble in water, alcohol, acids	0,951,15	—	—

Source: http://lkmprom.ru/clauses/issledovaniya/ingibitor-vliyanie-ingibitora-na-korroziyu-/

What are metal corrosion inhibitors and the mechanism of their operation, types of corrosion inhibitors, basis, properties of corrosion inhibitors

When it is difficult, if not impossible, to protect a metal structure from corrosion using a special coating, the time comes for inhibitor protection. Today you will learn what metal corrosion inhibitors (IC) are and how they work. We will talk about what types of corrosion inhibitors exist and what constitutes their basis. We will also discover what properties of corrosion inhibitors make the compositions indispensable in the fight against it.

Corrosion inhibitors are certain chemical compounds that can increase the corrosion resistance of metals. They are introduced directly into an aggressive environment, in which they exhibit their anti-corrosion qualities.

And since such environments can be different, metal corrosion inhibitors also differ in their properties and mechanism of operation or effect on metal.

Corrosion inhibitors produced by Conferum can exhibit their unique properties either independently or in combination with other drugs and methods.

Properties of corrosion inhibitors

The developers of our company, the leading manufacturer of inhibitors in Russia, give corrosion inhibitors such properties that allow them to create a mechanism of protective action against rust. The main property of corrosion inhibitors is to shield external influences and isolate the metal from the effects of an aggressive external environment.

Protection is provided by the adsorption of a corrosion inhibitor (IC) on the metal surface. By interacting with it at the molecular level, the inhibitor forms a new chemical compound, which in the form of a film covers the entire protected surface. The protective film should be as neutral as possible to external influences; it will not dissolve in this environment.

If these conditions are met, all the unique properties of the corrosion inhibitor will be fully demonstrated.

Finally, to fully understand what corrosion inhibitors are and how they work, it is helpful for you to know that IRs, according to ISO 8044-1986, are chemical compounds that are present in a corrosion system in sufficient concentration to reduce the rate of corrosion.

A prerequisite for their successful operation is that the concentration of any corrosive reagent should not change significantly. That is, a specific corrosion inhibitor, with its properties and qualities, is good in specific conditions. Therefore, if you find it difficult to choose an IC, we recommend contacting an online consultant on our website.

You will immediately receive competent advice.

Types of corrosion inhibitors

It is customary to distinguish the following types of corrosion inhibitors.

Cathodic, anodic and mixed according to their mechanism of action. Under the influence of corrosion inhibitors, the metal surface changes its state due to its adsorption (anodic protection) or forms poorly soluble compounds with metal cations (cathodic protection). In the first case, the active surface area decreases, in the second, the activity of the corrosion process decreases. Mixed types of corrosion inhibitors change the rate of both reactions.

Cathodic corrosion inhibitors are used in large-scale work, as they slow down the active dissolution and corrosion of metal due to a chemical reaction everywhere. Anodic inhibitors are more effective in preventing localized corrosion. To better protect metal from corrosion, it is advisable to use mixed compositions of inhibitors with various additives.

Based on their chemical nature, types of corrosion inhibitors are divided into inorganic and organic.

Inorganic corrosion inhibitors contain inorganic substances that can slow down metal corrosion in an aggressive environment.

The inhibitory properties of such compounds are ensured by the presence of cations (Ca2+, Zn2+, Ni2+, As3+, Bi3+, Sb3+) or anions (CrO2-4, Cr202-7, NO-2, SiO2-3, PO3-4). For iron in an aqueous environment, screening cathodic corrosion inhibitors can be more often Ca(HC03)2, less often ZnSO4, ZnCl2.

The cheapest cathodic inhibitor is calcium bicarbonate Ca(HC03)2. It is most often used for corrosion protection in water supply systems.

Anodic inorganic corrosion inhibitors are often also called corrosion passivators. They form a thin, about 0.01 micron layer of film on the metal surface, which inhibits the transition to corrosion of the metal. Types of film-forming inhibitors include NaOH, Na2C03 and phosphates.

It will be useful for you to know that so-called corrosion passivators can be dangerous if the concentration is incorrectly chosen. They are capable of not slowing down, but rather accelerating metal corrosion. If used incorrectly, they can result in very dangerous pitting corrosion.

Sodium and potassium chromates and dichromates are used as inorganic corrosion inhibitors for iron, galvanized steel, aluminum, copper, and brass in industrial water systems. Sodium hexametaphosphate is widely used in industry. Phosphates and polyphosphates are used as metal corrosion inhibitors in water and refrigeration brines. A greater effect, as evidenced by the many years of experience of the Conferum company, is achieved by using phosphates and chromates together.

Another type of corrosion inhibitors is organic. They contain organic compounds that can slow down metal corrosion. Organic compounds affect the rate of both cathodic and anodic reactions, so they are considered to be mixed-action inhibitors.

Their main difference from inorganic inhibitors is their ability to be adsorbed only on the metal surface. They are not interested in corrosion products. This feature of organic inhibitors is used in acid etching of metals to clean them from rust, scale, and scale.

Organic corrosion inhibitors include aliphatic and aromatic compounds containing atoms of nitrogen, sulfur and oxygen.

The most effective corrosion inhibitors in this series are made from functionally substituted quaternary (tertiary) ammonium compounds (FQACs) with derivatives of nonylphenols, neonols, alkylphenols with a functional group containing imidazoline, triazole, triazine, quinoline, pyridine, which are able to work in conditions of high temperatures in acidic environments.

Volatile inhibitors are a modern means of corrosion protection. They are indispensable for protecting metal structures and products from atmospheric corrosion during their storage and transportation. The operating principle of volatile corrosion inhibitors is based on the evaporation and formation of vapors, which settle on the metal surface, forming a protective nanolayer.

Types of corrosion inhibitors are further divided according to their sphere of influence; depending on their composition, they can work successfully in an acidic, alkaline or neutral environment.

Corrosion inhibitor base

As you now understand, the basis of a corrosion inhibitor is made up of chemical elements that can ensure its anti-corrosion qualities under certain conditions. We must say that the preparations produced by Conferum cannot always be strictly classified as a specific type of corrosion inhibitors.

Our developers, which include the country's leading chemist scientists, actively use a method called synergism. To put it simply and clearly, this is a successful mixture of different types and bases of corrosion inhibitors, which helps to increase the effectiveness of their action.

Synergism ensures the achievement of a greater protective effect than with the separate use of the same inhibitors and helps reduce the cost of manufactured products.

Cooperation with our company and active use of various types of corrosion inhibitors will allow you at least one of:

1.Lengthen the operating time of parts and equipment between repairs. This will reduce repair costs and increase production output by reducing downtime.

2. Reduce the cost of the constructed structure by using carbon and low-alloy steels instead of expensive corrosion-resistant materials.

3.Save fuel by improving heat transfer. Deposits of corrosion products on the walls of heat exchangers worsen their properties and render them inoperable.

4.Reduce losses from leaks of water and other liquids due to corrosion damage to the system.

In your specific conditions, a different effect can be achieved from the competent use of the unique properties of corrosion inhibitors in everyday work.

For example, energy consumption to overcome resistance from scale and other corrosive deposits in hydraulic systems can be reduced after the use of inhibitors. In any case, you now know what metal corrosion inhibitors are and how effective their mechanism of operation is. Know something else too.

There is a widespread belief among experts that for every ruble spent on purchasing corrosion inhibitors, you will receive five rubles in profit.

Anti-corrosion agent for metal surfaces

Protecting steel from corrosion

Protection of main pipelines Alazol

Anti-corrosion coating of metal during storage

Source: http://www.conferum.ru/chto-takoe-ingibitori-korrozii-matallov

Types and use of metal corrosion inhibitors - we describe all the nuances

Inhibitors are substances that suppress or delay the occurrence of a physicochemical process. In metal processing there is rust.

Metal inhibitors are elements that slow down or completely stop the rusting process. Substances are characterized by catalytic and chain reactions involving active particles.

Inhibitors and their main types

What are corrosion inhibitors? These are sulfur, nitrogen or oxygen, used in the form of various groups or compounds, but the development of polymer chemistry annually expands the list of substance inhibitors.

Today, the following types of metal corrosion inhibitors are distinguished:

• working in acid solutions;
• acting in alkaline solutions;
• used in neutral media and water;
• effective in preventing atmospheric corrosion;
• designed for exploration of oil deposits, their production, storage and transportation;
• anti-corrosion agents for secondary processing of petroleum products, as well as those effective against organic media.

These are quite large and conventional groups of substances and compounds. Inhibitors of each group can be divided according to their physical properties, mechanism of action, and method of application. But in general, all inhibitors can be divided into mixed, anodic and cathodic.

This division allows not only to determine their ability to interact with various reactions, but also to successfully determine the functional purpose of reaction inhibitors for a specific type of rust. In this case, chemists are guided by the degree of their influence on partial electrochemical reactions.

Source: https://wizard-aerosol.com/spetsialnye-materialy/chto-takoe-ingibitory-korrozii-metalla.html

Corrosion inhibitor: types, composition and methods of application:

A wide range of mechanical, chemical and electrochemical means are used to protect metal surfaces from corrosion. Most of them are used in direct connection with the target workpiece, which provides an insulating effect. But there is also a separate group of chemical compounds in the form of corrosion inhibitors, the principle of action of which is also oriented towards reducing the activity of the reagent itself, which provokes undesirable processes.

What is an inhibitor?

These are special substances or combinations of certain chemical elements that are introduced into the working environment in sufficient quantities to slow down or prevent corrosion processes. The effectiveness of this protection is assessed by two indicators: the corrosion stopping coefficient and the degree of protection of the metal itself.

In this case, the final effect will depend not only on the chemical compound itself, but also on environmental conditions, including the properties of the reaction, the characteristics of the aggressive environment and the physical and chemical parameters of the metal. Corrosion inhibitors primarily act in cases where a chain reaction occurs between the active center and aggressive particles. The protective compound acts specifically on the active elements, delaying, blocking or destroying them.

The nature of this effect and effectiveness in almost every case are individual, but the schemes are segmented depending on the type of product used.

Inhibitor compositions

Most often, compositions based on sodium nitrite are used, which are added to sodium silicates and phosphates, brines, sodium bichromates, sulfoxides, amines, tannin, etc.

Moreover, when using one or another inhibitor, it is important to take into account that the defense reaction involves its consumption, therefore it is periodically necessary to introduce new portions of the active element into the aggressive environment. For example, a typical composition of a corrosion inhibitor based on sodium nitrite is introduced in a volume of up to 0.05%.

Also, the active groups of compounds behave differently in certain environments. So, if the task is oxidation, then hydroquinone is taken as a basis, and to delay rust processes in relation to steel alloys, the use of technetium is recommended.

Specialized compounds include inhibitors for protection in environments with chlorine and hydrogen. In this case, nitrogen trichloride is used, but in minimal doses. As a rule, a thousandth of the total amount of reagents is enough to stop a negative interaction.

Classification of inhibitors by mechanism of action

The principle and characteristics of the formation of a protective environment are determined by the chemical nature of a specific formulation. In this sense, the following groups of compounds with anti-corrosion effect are noted:

• Adsorption. A monomolecular film is formed on the surface of the protected structure or part, which gradually stops negative electrochemical processes. Among such substances, surfactants are often found.
• Organic inhibitors. They represent products that give a mixed effect. They are able to inhibit anodic and cathodic destructive corrosion reactions. An organic inhibitor is often used in metal etching, facilitating further processes of cleaning surfaces from dirt and scale. At the same time, the structure of the metal itself remains the same and is not deformed.
• Inorganic inhibitors. An extensive group of compounds based on phosphates, silicates and polyphosphates. By combining elements of a chemical composition of this type, it is possible to obtain almost universal means for reducing the intensity of the process of structure destruction. The difficulty lies only in selecting a suitable active element for specific tasks.
• Passivating inhibitors. They form a protective film on the surface of the workpiece, which has a passivation effect. In other words, an oxidation reaction is performed (using nitrites and chromates, for example), in which the corrosion potential is reduced to the positive inactive side.

Neutral media inhibitors

Chemical inhibitors that protect against corrosion in neutral environments are classified as follows:

• With oxidizing properties. Chromates, nitrites and compositions including nitro- and carboxyl elements can be used individually or in combined compositions.
• Agents that promote the generation of sparingly soluble binders, but without oxidative action. These can be solutions of corrosion inhibitors based on borates and phosphates.
• Inhibitors with a weakened oxidative effect. What makes this category different is the content of anions like vanadates and molybdates.

Acid inhibitors

These are substances and elements that reduce the rate of the corrosion process that occurs in acids at a moderate concentration of 5 g/l. The function of anti-corrosion protection of this type is often performed by organic compounds. They are used when etching metals to remove scale from the surface. The effectiveness of rust retardation depends on the characteristics of the specific acid.

A corrosion inhibitor based on sulfur, oxygen and nitrogen is considered the most effective. Cationic inhibitors such as catapina, KPI-9, KPI-1, etc. are used especially for steel, aluminum, zinc and iron products.

Universal means of protecting metal in acid include the compositions KHOSP-10, KI-1, PB-8 and other products that demonstrate high ability for self-protection in aggressive environments.

Atmospheric corrosion inhibitors

This group includes contact and volatile inhibitors. The former are used directly on the metal surface, and depending on the composition, an impregnation effect can be achieved. Contact compositions include compositions containing nitrites, benzoates, etc.

These are mainly inorganic compounds that affect electrode kinetics. As for volatile corrosion inhibitors, this segment includes salts of amines and other weak acids. In particular, nitrites, benzoates, phosphates, etc. can be distinguished among them.

All of them tend to adsorb randomly on the surface of the workpiece, but are in a volatile state under normal temperature conditions.

Cathode and anodic inhibitors

Cathodic-type compositions slow down electrochemical reactions, which can cause corrosive processes due to the dissolution of metals. There is a decrease in the corrosion current as a result of a shift in the stationary potential of the cathode in the negative direction. Slightly soluble chemical films form on the surface of the material and bind to the depolarizer.

In turn, anodic metal corrosion inhibitors are considered more effective, since they also have an oxidative effect. Thanks to their support, a thin layer of passive anodic film is formed, which reduces the area of ​​​​corrosion. In essence, destructive processes are blocked. But it is important to consider that anodes can be dangerous if overdosed.

The rate of corrosion development will be reduced, but the rate of metal dissolution will increase.

Use of inhibitors at home

For general users, the most affordable means of corrosion protection using inhibitors is to apply a primer compound to the target surface.

This is a lightweight inhibitory coating, the effect of which is to prevent direct contact of water or an aggressive solution with the metal surface. Often paints and varnishes contain similar corrosion inhibitors.

Substances used for such purposes are produced in factories. These include red lead for the same primer, solutions of zinc or iron orthophosphates, phosphate coatings, etc.

The use of inhibitors when processing equipment

The most acute problems of protecting technical equipment are in agriculture, where the atmospheric environment negatively affects not just metal surfaces, but specifically welding joints. The tasks of treating vulnerable areas with protective agents are complicated by their location inside cavities.

Therefore, the use of corrosion inhibitors usually occurs as part of planned repairs using preservative compounds.

For temporary protection from biological and atmospheric influences, machines are treated with greases, oils, wax dispersions, gasoline-bitumen compounds, anti-corrosion additives, etc.

Application of inhibitors in the oil and gas industry

Basically, oil and gas pipelines are subject to corrosion damage, but not only. Metal and processing plant structures, downhole equipment, drilling rigs and accessories constantly interact with hydrogen sulfide, carbon dioxide and organic acids. It is obvious that in this case it is necessary to use specialized protective equipment.

In particular, corrosion inhibitors are used in the form of mixtures containing sulfur, nitrogen and methanol. The narrowing of the range of chemically active anti-corrosion agents available for use in this area is due to the fact that inhibitors should not in any way affect the technological processes of oil and gas enterprises (production, collection, preparation, processing of raw materials).

In addition, they must have acceptable toxicity to the environment.

Conclusion

Modern means of protecting materials from negative environmental factors are increasingly focused on subtle physical and chemical reactions and processes that result in changes in the structure of materials. This is precisely the approach that inhibitors demonstrate in the most effective models of protection.

Special solutions sometimes prevent destruction of the metal surface at the molecular level, preserving its performance qualities in its original form. But there are other examples, including penazoline (surfactant) - a corrosion inhibitor that has a dual surface effect.

Like traditional anti-corrosion coatings, it forms a rough, thick film that physically prevents aggressive environments from attacking the metal.

That is, for almost any conditions with a risk of corrosion, modern industrial chemistry can offer a worthy means of protection - all that remains is to correctly calculate the properties of the composition and outline the requirements for its use.

Source: https://www.syl.ru/article/418852/ingibitor-korrozii-vidyi-sostav-i-sposobyi-primeneniya

What are corrosion inhibitors, their types and rules of use

Under the influence of external factors, all materials change some of their properties to one degree or another. One of them that directly affects the destruction of the structure of substances is liquids.

When we talk about corrosion, we mainly mean the contact of various parts or structural elements with water (or media containing it), although there are other types of it - electrical/chemical, gas, and the like.

Such contact can be not only direct (getting wet), but also indirect. For example, in conditions characterized by excess humidity.  

All substances that have a negative effect on materials are called aggressive and, according to the degree of influence (intensity of destruction), are divided into strong, medium or weak effects. Naturally, to extend the life of products it is necessary to take care of their effective protection.

The most common methods are:

• application of protective films (polymers and a number of other chemical compounds);
• surface treatment with a layer of more “stable” metal;
• coating with cement (for example, utility pipes - sewerage, water supply, etc.);
• painting with enamels;
• electrochemical treatment with the formation of a layer of phosphates;
• priming with special compounds.

There are other, more expensive methods. For example, doping. Many of them are applicable only in production, as they require the use of appropriate equipment and are characterized by complex technology.

Inhibitors - what are they?

In the “private” sector, the master’s capabilities are limited. Therefore, in many cases it is preferable to reduce the aggressiveness of the environment using special compounds. Such substances are called “corrosion inhibitors”.

Advantages of the method:

1. Easy to use.
2. The ability to carry out operations without the use of expensive equipment and at all stages of construction or repair.
3. Economical.

We will not bother the reader with reading a description of all the nuances of the ongoing chemical processes. For general information, we just note that corrosion inhibitors are divided into absorption and passivation. In practice, the function of protecting metals is performed either by one product or by several (a mixture of them).

Types of inhibitors

• for acidic environments;
• from atmospheric influence;
• against hydrogen sulfide corrosion;
• for storage facilities and pipelines with petroleum products;
• for neutral environments.

In turn, all groups have an “internal classification”. For example, substances are divided into organic, inorganic and volatile; mixed, cathodic or anodic.

Regardless of its chemical composition, the same product behaves differently in a given aggressive environment.

Main characteristics

1. Pour point.
2. Viscosity.
3. Density.
4. Solubility.
5. Flash point.

Where can inhibitors be used?

It is worth reminding the reader that the term “corrosion” does not only apply to metals. For example, ceramics, polymers and other materials are subject to destruction under the influence of aggressive chemical compounds. But in this case it is customary to use the word “aging”.

Scope of application

We will not consider the issue of using inhibitors on an industrial scale. Subject matter experts know this very well. They are even added to fuels and lubricants to minimize the activity of an aggressive environment. We will note only those “structural elements” that can be protected with the help of special means in the “private” sector.

• Pipe lines, especially sections laid across the territory (outside the building).
• Septic tanks whose tanks are made of metal.
• Roof, walls, foundation.
• Heating systems. To prevent internal corrosion (or “rusting” - there is such a term) of pipes and radiators.

The range of products is quite large. Here are just a few of the types of commercially available products.

"Inhibit"

Used to protect many metals and alloys. It is advisable to treat structures operating in excess humidity, even at temperatures below 0 ºС (down to -40). After application, the product forms a thin film. Before use, it is diluted with almost all available solvents - toluene, white spirit and some others.

Price per package – from 245 rubles.

"RE-Therm"

It is considered a universal product, since the range of applications is very wide - from processing roofing material and pipelines (air ducts) to parts (for example, the underbody) of a personal car. The solvent is ordinary water.

Price – from 480 rubles.

Source: https://masterim.guru/strojmaterialy/ingibitory-korrozii/

Efficiency

The inhibitor efficiency coefficient depends on two indicators. These include:

1. a percentage of corrosion protection equal to “0” means that there is none;
2. The percentage of protection effect indicates a slowdown in the corrosion process.

These indicators make up the overall effectiveness of the substance used.

Classification

Classification by type of environment is widely used:

• Neutral environment inhibitors;
• Atmospheric environment;
• acidic environment inhibitors;
• hydrogen sulfide corrosion;
• oil media inhibitors.

Neutral separation

There are different types of inhibitors for neutral media. According to Rosenfeld's theory, they are divided into:

• components having oxidizing properties;
• substances that form sparingly soluble compounds without oxidizing properties;
• agents that have a slight oxidative effect with anions.

The most common is sodium nitrite, used when metal and water react. An increase in temperature reduces its effect, which requires an increase in concentration. Its activity depends on the volume of chlorides. Non-toxic phosphates are used in cooling systems.

The effectiveness of this material is not dependent on the presence of chlorides. Chromates are a universal remedy and can be used on any alloy. Their activity decreases significantly with increasing temperature. You will need to double the concentration for every +30°C.

Manifestation of atmospheric corrosion

To save iron from atmospheric influences and corrosion, contact or volatile inhibitors are needed. Their distinctive abilities:

1. The contact inhibitor is sprayed onto the outside of the product; materials can be impregnated with it. This includes non-organic compounds that affect the kinetic energy in the electrodes. They can be found in GOST 9.014–78. A distinctive characteristic is the low volatility of the material. They protect the metal surface or make it passive to negative influences.
2. Volatile - adsorbed on the metal by themselves. At standard temperatures they have a volatile state. Have a direct effect on the kinetic energy in the electrodes. This includes salts of organic and inorganic acids, as well as amines. On iron they are placed as a homogeneous layer of molecules, where they interact with metal parts. They transform the metal into a passive state and slow down the reaction. Their influence depends on the composition of the anti-corrosion agent and its structure, as well as the method of evaporation. Produced in strict accordance with GOST 16295-77. Available in models UNI-14-40, UNI-22-80 and UNI-14-80. They are an equivalent compound of hexamine and sodium nitrite, where the first 2 digits indicate the weight in grams. Capable of protecting ferrous metal alloys, steel with chromium and oxides.

Each inhibitor has its own characteristics. This makes it possible to select substances to achieve the desired result.

For acidic environment

In an acidic environment, inhibitors significantly reduce the corrosive effect. The feature is as follows:

• average concentration 5 g/l;
• Organic and inorganic compounds can be used, the former are used more often;
• The main purpose of use is metal etching.

These elements have a long history since the Middle Ages, when they were used by gunsmiths. At that time they were used in combination with flour and waste from its production. They inhibit the corrosion process due to increased polarization of the anodic, cathodic or mixed process. An example is the FM inhibitor, PAV-446, KI-1.

For hydrogen sulfide corrosion and petroleum environments

They are used at all stages of production, refining and transportation of oil and its products. They have their own distinctive features:

• they have paraffin-forming properties;
• prevent foaming;
• counteract ignition.

Examples include ISA-148, Corexit-6350. Each medium has its own inhibitor composition. It is important to note that one substance acts differently in different environments.

Varieties by method of exposure

According to the mechanism of action, they are divided into types:

1. The passivating inhibitor covers the part with a film. Often, inorganic compounds that have oxidizing properties are used in their role. This increases the corrosion resistance potential. They are more effective than non-passivating agents.
2. Adsorption agents are sprayed onto the product with a film. Quite often, active substances and organic compounds appear in this form. They enhance the effectiveness of the film. In this way, oxygen improves the protective effect. The correct selection of inhibitors provides greater effectiveness, which allows you to achieve high efficiency.

According to the method of protective action

The inhibitor works in an electrical, chemical mechanism. It acts on anodic, cathodic or complex corrosion processes and slows down their effects. Let's look at the possible options in more detail:

1. Anode additives affect the reaction of the anode. A thin passive protective film is formed on the anode of the product. It slows down the process of corrosion development. It is called a passivator. Their activity lies in the fact that, due to the formed protective film, the transition of the metal structure to the liquid state slows down. When using them, it is important to accurately select their quantity and composition. If the proportions are violated, the impact of corrosion becomes greater. When their quantity is small, the result is a slowdown in corrosion in certain places and an increase in this process in other areas.
2. Cathode components stop the cathode reaction, the transition of iron to a liquid state. The potential goes in the negative direction, resulting in a decrease in the corrosion current. A protective film appears on the surface, and the depolarizer is firmly bound. The protective compound is difficult to dissolve, firmly blocks the protected part and slows down the corrosion process. They have less efficiency compared to anodic or mixed substances. Their use is strictly limited. Due to their lack of efficiency, they do not work in acidic environments. These include hydrazine, sodium sulfate.
3. The mixed inhibitor slows down the anodic and cathodic chemical reactions. For this reason, they are considered the most effective of their kind. Their main part works according to the oxidative type. These include chromates.

The final result depends on the quality of inhibitors and the correct selection. The most popular is a mixed type substance.

By chemical nature

The division according to the chemical nature of the application is as follows:

1. Volatile inhibitors available in spray form.
2. Compounds of mixed type are suitable for organic inhibitors. They slow down the anodic and cathodic reactions. They are often used in acid etching. Foreign objects in the form of scale and rust are removed. There is only one metal left. The quality of the work process depends on the concentration, temperature conditions and other capabilities of the materials. The composition of this substance includes oxygen, sulfur and nitrogen. They are placed only on iron products.
3. The non-organic inhibitor is most often used. This includes anodic, cathodic, and film-forming substances. The effectiveness depends on their composition and affects the slowdown of the rate of corrosion.

As you can see, the inhibitor must be selected very carefully. For high efficiency of its use, it must meet a number of requirements laid down in the technical characteristics.

Only with strict adherence to these requirements can corrosion be overcome, high performance achieved and the service life of the material extended.

Source: https://prompriem.ru/korroziya/ingibitor-korrozii.html

Metal corrosion inhibitors: features and principle of protection

Corrosion inhibitor: what is it? Translated from Latin, the word “inhibitors” means “delays.” They are quite widely used in domestic industry.

Metal corrosion inhibitors are a group of special substances and compounds whose main purpose is the comprehensive protection of metal structures from the destructive effects of corrosion. Such substances are added to polymer coatings, waxes, lubricants, packaging, and closed spaces in which metal is stored. The result is an increase in the protective capabilities of coatings.

Means for protecting metals from corrosion are divided into types based on:

• Mechanism of action: adsorption and passivating reagents.
• Environments for the functioning of structures: compounds that protect against rust in acidic, neutral and hydrogen sulfide environments; special substances used in oil wells.
• Chemical nature: organic and inorganic, volatile inhibitors.
• Principle of protective action: cathodic, anodic or combined compositions.

The effect of these substances is based on one principle: the state of surfaces changes, which results in the formation of sparingly soluble compounds with metal cations or as a result of the absorption of the specific inhibitor used.

Substances and compounds that can stop the process of corrosion development can act on iron in two ways . In the first case, the activation energy is modified during the rusting process, and in the second case, the area of ​​surfaces that are called corrosive is reduced.

The thickness of the layer formed by useful substances is less than the thickness of the applied coating. In particular, passivators can form a special film that will shift the corrosion potential in a positive direction. We are talking about molybdates, nitrites and chromates, which have excellent anti-corrosion effects.

Adsorption compounds absorb the top layer of the processed metals, creating a special thin film on them. It is this that significantly slows down, and in some cases even stops, electrochemical type corrosion that forms on surfaces.

Weather protection

To protect iron alloys, contact and volatile substances are used, which quickly evaporate and are independently distributed over surfaces.

Volatile compounds are used due to the significant requirements for barrier materials:

• Impermeability to vapors of useful compounds.
• Ensure that the packaging is sealed, otherwise the substances will evaporate.

Several application methods are used to preserve metal products from atmospheric influences:

• Treating surfaces with aqueous solutions or organic solvents.
• Carrying out the process of sublimation of inhibitors on the surface of products from air with a significant concentration of useful compounds.
• The materials are coated with polymer compounds, the components of which are necessarily inhibitors.
• The products are wrapped in a layer of inhibited paper.
• Porous carriers with the necessary connections are directed in a closed space.

In the latter case, the protective functions are performed by the drugs “Linopon” and “Linasil”. These substances, when placed in enclosed spaces, can ensure the long-term integrity of the metal - it will practically not be subject to corrosion and “bronze disease”. Such structures can be preserved in the event of significant temperature changes.

Preservation using inhibitors is recommended to be carried out at a humidity level below critical, in clean air . Avoid the presence of acidic fumes in work areas; such fumes are released during dry cleaning).

Please note that the substances are not absorbed instantly; it will take some time for protection to form. The duration depends not only on the selected substances, but also on the structure of the elements being processed. Before processing, metals are cleaned of accumulations of dirt and grease and dried.

Be careful: before starting conservation, the iron should not be touched with your hands, and all work should be carried out exclusively with rubber gloves!

Protection for steel structures

Liquid solutions of sodium nitrite are very popular. This substance belongs to contact-type inhibitors that are applied to the surfaces of products (for example, heating systems or other metal devices).

It is advisable to add additional components to sodium nitrite to increase the viscosity of the structure (we are talking about hydroxyethylcellulose, glycerium, xylitol, starch) - this significantly increases the effectiveness of the substance used. You can increase the protection period of structures regardless of climatic conditions. The viscous composition will not allow sodium nitrite to dry out, salt crystals will not move away from surfaces, and the percentage of substances running off in conditions with high humidity will also be reduced.

In most cases, a solution of 25% sodium nitrite is used to protect steel products, and 40% for cast iron. The solution is preheated to a temperature of 65−85 degrees.

Source: https://tokar.guru/metally/chto-takoe-ingibitory-korrozii-metalla.html

Corrosion inhibitor - what is it? Classification, application and properties

Metals and some other materials are susceptible to corrosion. If corrosion destroys the structure of the material, then the product loses its performance qualities, which leads to emergency situations. One way to solve this problem is metal corrosion inhibitors.

Description of inhibitors

What is a corrosion inhibitor? Corrosion inhibitors are special substances that stop (delay) the process of chemical and physical reactions. Corrosion inhibitors occupy a special place among such substances.

Inhibitors include agents that form a special protective film on the metal surface, which is obtained during the reaction of an inhibitor solution and corrosion products.

The emergence of compounds that slow down corrosion processes was a breakthrough. At the moment, most methods of protection are protection using inhibitors. The most popular substances in this capacity are amines, nitrogen-containing substances, urea, sulfides, aldehydes, etc.

The effectiveness of protective processes involving inhibitors directly depends on the metal, the characteristics of the external environment, pressure on the material, etc.

It is worth noting that the corrosion inhibitor protection does not work constantly; when the additive gets into the solution, it gradually dissolves, so in the future it is necessary to add it to an aggressive environment in small portions.

Types and uses of metal corrosion inhibitors

The main types of inhibitors include:

• Cathode – reduce the rate of cathodic interaction.
• Anodic - inhibit the dissolution of the anode.
• Mixed - additives that slow down reactions, both cathodic and anodic.

There is a classification of inhibitors by origin:

• Organic are organic substances that are more versatile because they reduce the rate of cathodic and anodic reactions. These include nitrogen, sulfur, oxygen, and aromatic compounds. The main advantage and difference from inorganic inhibitors is the fact that organic substances are adsorbed only on the surface of the material, without reacting with rust.
• Inorganic corrosion inhibitors, what are they? They contain inorganic substances as part of the inhibitor. The peculiarity of working with inorganic particles in an inhibitor is that if the concentration is incorrectly selected, they may not protect the metal by forming a thin film on it, but rather react with corrosion products and accelerate the destruction process. Includes chromates, sodium and potassium bichromates, calcium bicarbonate, etc.

The principle of action of inhibitors

Common Types of Acid Inhibitors

The most economical anti-corrosion inhibitor is acidic. Its consumption in the process of metal etching is minimal, which entails a reduction in the cost of the product and the protection procedure as a whole.

The properties of acid inhibitors can also be supplemented by the fact that when applied to a material, it also cleans it of the formed scales and various oxide films. Also, the additive does not change its properties, is not transformed, and is not destroyed when the ambient temperature increases.

On the domestic market you can most often find such corrosion inhibitors as I-5-V and I-5-VM. These additives are intended for products made of low-carbon, medium-carbon and high-carbon and alloy steels. They are effectively used in industry, and both inhibitors can be combined with each other.

The use of corrosion inhibitors with this composition reduces metal waste, helps clean the surface of the etched material, and also has a beneficial effect on sanitary and hygienic working conditions.

Cathodic corrosion inhibitor

This type of additive slows down the dissolution of metal during the cathodic process. The system potential moves from its usual neutral state to the negative side, which leads to a decrease in the corrosive current, and an anti-corrosion film is formed on the surface. This film is difficult to dissolve not only under normal conditions, but also for many aggressive environments. It becomes a barrier between the external environment and the metal, maintaining its integrity.

What is cathodic inhibitor corrosion protection? Most often, these are compounds that increase the acidity of the environment, which reduces the possibility of metal dissolution.

Cathode additives are not used in acidic environments, as they are not effective there.

As noted earlier, the inhibitor must be dissolved in some substance before use, the simplest one being water. Experts select the correct concentration of the additive in a given volume of water.

It is worth noting that this type of substance is the least effective in comparison with anodic and mixed inhibitors.

Anodic corrosion inhibitors

These substances are passivators - substances that pass from an active state to a passive state and form a film. This film protects the metal element. Corrosion slows down due to a decrease in the rate of transition of metal ions into the solution, and the area of ​​the anodic areas covered with the film decreases due to their separation.

It is the anodic additives, if you overdo them, that may not reduce, but accelerate the corrosive destruction of the material. Carbonates, silicates, phosphates, and sodium nitrite are popular as anodic corrosion inhibitors.

Mixed corrosion inhibitors

Mixed additives are chromates. Chromates significantly inhibit the anodic and cathodic reactions together, which is why they are the most effective. The process of such a reaction proceeds according to the oxidative type.