The word corrosion comes from the Latin "corrodo" - "gnaw" (Late Latin "corrosio" means "corrosion"). Corrosion is caused by the chemical reaction of a metal with environmental substances occurring at the interface between the metal and the medium. Most often, this is the oxidation of a metal, for example, with atmospheric oxygen or acids contained in solutions with which the metal comes into contact. Metals located in the voltage series (activity series) to the left of hydrogen, including iron, are especially susceptible to this.

Chemical corrosion t Fe+ 3 SO O 2 Fe 2 (SO 4) t Fe + 3 Cl 2 2 FeCl t Zn + O 2 2 ZnO Corrosion occurs in a non-conductive medium. For example, the interaction of a metal with dry gases or liquids - non-electrolytes (gasoline, kerosene, etc.)

Many metals (for example, aluminum) during corrosion are covered with a dense, oxide film, which does not allow oxidizing agents to penetrate into deeper layers and therefore protects the metal from corrosion. When this film is removed, the metal begins to interact with moisture and oxygen in the air.

Electrochemical corrosion Corrosion occurs in a conductive medium (electrolyte) with the appearance of an electric current inside the system. Metals are not homogeneous and contain various impurities. When they come into contact with electrolytes, some parts of the surface act as anodes, others as cathodes.

Let us consider the destruction of an iron sample in the presence of a tin impurity. 1. In an acidic environment: On iron, as a more active metal, in contact with the electrolyte, the processes of oxidation (dissolution) of the metal and the transition of its cations to the electrolyte occur: Fe 0 - 2 e \u003d Fe 2+ (anode) At the cathode (tin) occurs reduction of hydrogen cations: 2H + + 2e H 2 0 iron ions (Fe 2+) go into solution

2. In an alkaline or neutral environment: Fe 0 - 2e Fe 2+ (at the anode) O H 2 O + 4e 4OH - (at the cathode) ________________________________________________________ Fe OH - Fe (OH) 2 4 Fe (OH) 2 + O 2 + 2H 2 O = 4 Fe (OH) 3 (Rust)

1. Sanding the surfaces of the product so that moisture does not linger on them. 2. The use of alloyed alloys containing special additives: chromium, nickel, which at high temperatures form a stable oxide layer on the metal surface (for example, Cr 2 O 3). forks, spoons), machine parts, tools.

3. Application of protective coatings Non-metallic - non-oxidizing oils, special varnishes, paints, enamels. True, they are short-lived, but they are cheap. Chemical - artificially created surface films: oxide, nitride, silicide, polymer, etc. For example, all small arms and parts of many precision instruments are burnished - this is the process of obtaining the thinnest film of iron oxides on the surface of a steel product.

Metallic is a coating with other metals, on the surface of which stable protective films are formed under the action of oxidizing agents. Application of chromium - chromium plating, nickel - nickel plating, zinc - zinc plating, etc. A chemically passive metal - gold, silver, copper - can also serve as a coating.

4. Electrochemical methods of protection 4. Electrochemical methods of protection * Protective (anodic) - a piece of a more active metal (protector) is attached to the protected metal structure, which serves as an anode and is destroyed in the presence of an electrolyte. Magnesium, aluminum, zinc are used as a protector in the protection of ship hulls, pipelines, cables and other steel products.

The introduction of substances - inhibitors that slow down corrosion. Examples of the use of modern inhibitors: during transportation and storage, hydrochloric acid is perfectly "tamed" by butylamine derivatives, and sulfuric acid - by nitric acid; volatile diethylamine is injected into various containers. Inhibitors act only on the metal, making it passive in relation to the environment. More than 5 thousand corrosion inhibitors are known to science. Removal of oxygen dissolved in water (deaeration). This process is used in the preparation of water entering boiler plants. 5. Special treatment of the electrolyte or other environment in which the protective metal structure is located

• We must find out what is the corrosion of metals?
• What are the types of corrosion?
• How is this process going?
• What is the role of corrosion in the life of human society and why study it?
• What are the ways to protect against it?

• The concept of corrosion
• Types of corrosion
• Chemistry of the corrosion process
• Significance of corrosion
• Corrosion protection methods

Corrosion

comes from the Latin corrosio,

which means to destroy, destroy.

• Rust that appears on the surface of steel and cast iron products is a prime example of corrosion.
• Rusting refers only to the corrosion of iron and its alloys. Other metals corrode but do not rust.
• Corrosion of metals is a spontaneous process of destruction of metals and products from them under the influence of the environment.

Corrosion classification

By the nature of the destruction:

1. continuous corrosion, distributed evenly over the entire surface of the metal or alloy (for example, the process of rusting of iron alloys in air or their interaction with strong acids).

2. local (local) corrosion, covering individual areas:

• spots;
• ulcerative;
• point
• through;

• chemical corrosion;

• electrochemical corrosion.

Chemical corrosion of metals

this is the destruction of metals as a result of their direct chemical interaction with environmental substances.

The most common type of chemical corrosion is gas corrosion, which occurs in dry gases in the complete absence of moisture. The gaseous substance of the environment reacts with the metal on the surface of the metal product and forms compounds with it.

2Fe+3SO 2 +3O 2 → Fe 2 (SO 4 ) 3

2Fe+3Cl 2 →2 FeCL 3

Experience number 1. Influence of various electrolytes on the corrosion rate of metals (depending on pH).

• test tube No. 1 -3 ml NaCl, pH=7
• test tube No. 2 - 3 ml NaCl + 2 drops of NaOH, pH=12
• test tube No. 3 - dist. water + 2 drops H 2 SO 4 , pH=2
• test tube No. 4 - distilled water, pH=7
• test tube No. 5 - tap water, pH determined by universal indicator paper.

Add 2 drops of red blood salt solution, K 3 to all test tubes and dip into each iron nail.

Solution composition

Sequence of staining

H2O plumbing.

Electrochemical corrosion is the destruction of metals, which is accompanied by the occurrence

electric current.

With electrochemical corrosion

(most common form of corrosion)

an electrolyte is always required (condensate, rainwater, etc.),

with which the electrodes are in contact

either different elements of the material structure, or two different contacting materials with different redox potentials.

A corrosive element is formed.

It is nothing more than a closed galvanic cell. In it, a slow dissolution of the more active metal occurs,

the second electrode in a pair, as a rule, does not corrode.

Experience number 2. Chemical and electrochemical corrosion of zinc.

Influence of the formation of galvanic couples on the corrosion rate of zinc.

• Pour 3 ml of 2 N hydrochloric acid solution into two test tubes and add one granule of zinc. Observe the release of gases in the test tubes. Make up the chemical and electronic equations of the ongoing reaction.
• Insert a copper wire into one of the test tubes without touching a piece of zinc.

Does copper react with acid?

• Lower the copper wire until it contacts the zinc granule

What's happening? Observe the evolution of hydrogen from the copper surface and the reaction rate compared to the first tube. What is the anode and cathode in this case?

Make electronic equations of electrode processes.

Consider the electrochemical corrosion of an iron sample with tin inclusions. Iron is a more active metal. Upon contact with the electrolyte, some of the iron atoms, being oxidized, go into solution:

Fe 0 -2e = Fe 2+ (anode) is destroyed.

in an acidic environment. Hydrogen ions are reduced on tin (cathode):

2H + + 2e- \u003d H 2

Fe 0 + 2Н + → Fe 2+ + Н 2

In alkaline and neutral environment. On tin (cathode) oxygen dissolved in water is reduced

O 2 + 2H 2 O + 4e → 4OH -;

iron ions Fe 2+ react with hydroxide anions

Fe 2+ + 2OH - → Fe (OH) 2.

4Fe (OH) 2 + O 2 + 2H 2 O \u003d 4 Fe (OH) 3

4Fe + 3O 2 + 6H 2 O \u003d 4 Fe (OH) 3

Fe(OH) 3 is rust.

Metals have an enemy that leads to huge
irretrievable losses of metals, annually completely
about 10% of the iron produced is destroyed. By
according to the Institute of Physical Chemistry of the Russian Academy of Sciences, each
the sixth blast furnace in Russia is running in vain - the entire
the smelted metal turns into rust.
That enemy is corrosion.

The problem of protecting metals from corrosion
arose almost at the very beginning of their
use. People tried to protect
metals from weathering with
with the help of fats, oils, and later
coated with other metals and, before
all, low-melting tin (tinning). AT
writings of the ancient Greek historian Herodotus
(V century BC) there is already a mention of
the use of tin to protect iron from
corrosion.

In the III BC on the island of Rhodes was built
lighthouse in the form of a huge statue of Helios.
The Colossus of Rhodes was considered one of the seven wonders of the world,
however, it lasted only 66 years and collapsed during
earthquakes. At the Colossus of Rhodes bronze
shell was
mounted on
iron frame.
Under the action of wet
saturated with salts
mediterranean air
the iron frame collapsed.

In the 20s of the twentieth century. commissioned by a millionaire
The luxury yacht “Call of the Sea” was built.
Even before entering the open sea, the yacht is completely
out of order. The reason was the contact
corrosion. The bottom of the yacht was sheathed in copper-nickel alloy, and the rudder frame, keel and other
parts are made of steel. When the yacht was
launched into the water. A gigantic
galvanic cell, consisting of a cathode, a steel anode and an electrolyte - marine
water. As a result, the ship sank without making any
one flight.

What is a symbol
Paris? –Eiffel
tower. She is incurable
sick, rusty and
collapses and only
constant
chemotherapy helps
fight with it
deadly disease:
she was painted 18 times, why
its weight is 9000 tons
every time
increases by 70 tons.

Corrosion is the destruction of metals and
alloys under the influence of the environment
environment. The word corrosion comes from
Latin corrodere, which means
fret.

Types of corrosion

Chemical corrosion

Chemical corrosion -
this interaction
metals with dry
gases and liquids -
non-electrolytes.
This kind of corrosion
turbines are exposed
furnace fittings and parts
internal engines
combustion.

Electrochemical corrosion

Electrochemical
corrosion is everything
cases of corrosion
the presence of water and
liquids -
electrolytes.

essence of corrosion.

Corrosion is made up of
two processes:
chemical is
donating electrons and
electrical is
electron transfer.

Patterns of corrosion:

1. If connected
two different metals
then corrosion
exposed only
more active and
until he is completely
will not collapse, less
active protected.

Patterns of corrosion:

2. Corrosion rate
the more than
further apart
in a series of voltages
located
connected
metals.

Corrosion chemistry.

Corrosion protection methods.

One of the most common
ways to protect metals from corrosion
is applied to their surface
protective films: varnish, paint, enamel.

Widespread method of protection
metals from corrosion is coating them
layers of other metals. Covering
metals themselves corrode with little
speed, as they are covered with dense
oxide film. Produce coating
zinc, nickel, chromium, etc.

Coating with other metals.

In everyday life, people most often
meets with coatings of iron with zinc and
tin. sheet metal, coated
zinc is called galvanized iron,
and covered with tin - tinplate. First
in large quantities goes to the roof
houses, and from the second they make
cans.

Corrosion protection methods.

Create alloys with
anticorrosive
properties. For this
into base metal
add up to 12%
chrome, nickel,
cobalt or copper.

Corrosion protection methods.

Line-up change
environment. For
corrosion inhibition
introduced
inhibitors. it
substances that
slow down the speed
reactions.

Corrosion protection methods.

The use of inhibitors is one of the effective
ways to combat corrosion of metals in various
aggressive environments (atmospheric, in sea water, in
coolants and salt solutions, in
oxidizing conditions, etc.). Inhibitors are
Substances capable of slowing down in small quantities
the flow of chemical processes or stop them.
The name inhibitor comes from lat. inhibere that
means to stop, stop. It is known that
damascus masters for scale and rust removal
used solutions of sulfuric acid with additives
brewer's yeast, flour, starch. These impurities were
one of the first inhibitors. They didn't let the acid
act on weapon metal, resulting in
only scale and rust were dissolved.

Electrical protection.

1. Tread protection.
to the main structure
attached
rivets or plates
from a more active
metal, which
exposed
destruction. Such
protection is used in
underwater and underground
structures.

Electrical protection.

2. Passing
electric current
in the direction,
opposite
the one who
occurs in the process
corrosion.

Description of the presentation PRESENTATION on the topic "" Corrosion of metals on slides

Corrosion of metals Introduction Chemical corrosion Electrochemical corrosion The essence of corrosion processes Methods of protection against corrosion Atmospheric corrosion of steel Metal corrosion inhibitors

Introduction The word corrosion comes from the Latin corrodere, which means to corrode. Although corrosion is most commonly associated with metals, it also affects stones, plastics and other polymeric materials, and wood. For example, at present we are witnessing a great concern of the general public due to the fact that monuments (buildings and sculptures) made of limestone or marble are catastrophically affected by acid rain. Thus, corrosion is called a spontaneous process of destruction of materials and products from them under the chemical influence of the environment. The processes of physical destruction are not classified as corrosion, although they often cause no less harm to cultural monuments. They are called abrasion, wear, erosion.

Metals are one of the foundations of civilization on planet Earth. Among them, iron clearly stands out as a structural material. The volume of industrial production of iron is about 20 times greater than the volume of production of all other metals combined. The widespread introduction of iron in industrial construction and transport occurred at the turn of the 18th century. . . 19th century At this time, the first cast-iron bridge appeared, the first ship was launched, the hull of which was made of steel, and the first railways were created. However, the beginning of the practical use of iron by man dates back to the 9th century. BC e. It was during this period that humanity moved from the Bronze Age to the Iron Age. Nevertheless, history testifies that iron products were known in the Hittite kingdom (the state of Asia Minor), and its heyday is attributed to the XIV. . . 13th century BC e.

In nature, although very rarely, native iron is found. Its origin is considered meteorite, that is, cosmic, and not terrestrial. Therefore, the first iron products (they were made from nuggets) were highly valued - much higher than those made from silver and even gold.

Despite the widespread introduction of polymeric materials, glass, and ceramics into our lives today, the main structural material continues to be iron and alloys based on it. We meet with iron products at every step in everyday life and we know how much trouble its rust and rust itself cause. Rusting refers only to the corrosion of iron and its alloys. Other metals corrode but do not rust. Although almost all metals corrode, in everyday life a person most often encounters iron corrosion.

Chemical corrosion Chemical corrosion of steel is caused by dry gases and liquids that do not have the character of electrolytes, such as organic compounds or solutions of inorganic substances in organic solvents. Chemical corrosion is not accompanied by the appearance of an electric current. It is based on the reaction between a metal and an aggressive reagent. This type of corrosion proceeds mostly uniformly over the entire surface of the metal. In this regard, chemical corrosion is less dangerous than electrochemical.

Corrosion products can form a dense protective layer on the metal surface, which inhibits its further development, or a porous layer that does not protect the surface from the damaging effects of the environment. In this case, the corrosion process continues until the complete destruction of the material or a period of time until the aggressive environment acts. Most often in practice, gas corrosion of steel occurs, caused by exposure to O 2, SO 2, H 2 S, CI, HC 1, NO 3, CO 2, CO and H 2.

Electrochemical corrosion Electrochemical corrosion occurs when metals interact with liquid electrolytes, mainly solutions of acids, bases and salts. The mechanism of the corrosion process depends on the structure of the metal, as well as on the type of electrolyte. Steel, like any metal, has a crystalline structure in which the atoms are arranged in the appropriate order, forming a characteristic spatial lattice. Iron crystals have a structure that differs significantly from the ideal scheme, since there are voids not occupied by metal atoms, cracks, inclusions of impurities in gases.

Metals have good electrical conductivity, which is due to the presence of free electrons, the movement of which creates an electric current. The number of free electrons corresponds to the equivalent number of ion-atoms, i.e., atoms that have lost one or more electrons. In the case of a potential difference at the ends of a metal rod, the electrons move from the pole with the highest potential to the opposite pole. Metals with electronic conductivity are conductors of the first kind, and electrolytes that have ionic conductivity are conductors of the second kind.

Depending on the type and content of salts dissolved in water, not only normal potentials change, but even the position of the metal in the series of potentials.

Essence of corrosion processes. Corrosion of metals is most often reduced to their oxidation and transformation into oxides. In particular, the corrosion of iron can be described by the simplified equation 4 Fe + 3 O 2 + 2 H 2 O = 2 Fe 2 O 3 H 2 O Hydrated iron oxide Fe 2 O 3 H 2 O and is what people call rust . It is a loose powder of light brown color. During corrosion, many metals are covered with a dense, well-bonded oxide film with metals, which does not allow air oxygen and water to penetrate into deeper layers and therefore protects the metal from further oxidation. For example, aluminum is a very active metal and theoretically should interact with water in accordance with the equation 2 Al + 3 H 2 O = Al 2 O 3 + 3 H

It is difficult, and sometimes impossible, to strictly separate chemical corrosion from electrochemical corrosion. The fact is that electrochemical corrosion is often associated with the presence of random impurities or specially introduced alloying additives in the metal.

Corrosion protection methods. The problem of protecting metals from corrosion arose almost at the very beginning of their use. People tried to protect metals from atmospheric action with the help of grease, oils, and later by coating with other metals and, above all, with low-melting tin (tinning). In the writings of the ancient Greek historian Herodotus (5th century BC), there is already a mention of the use of tin to protect iron from corrosion.

Cement coatings are used to protect cast iron and steel water pipes from corrosion. Since the coefficients of thermal expansion of Portland cement and steel are close, and the cost of cement is low, it is quite widely used for these purposes. The disadvantage of Portland cement coatings is the same as enamel coatings - high sensitivity to mechanical shocks.

A common way to protect metals from corrosion is to coat them with a layer of other metals. The coating metals themselves corrode at a low rate, as they are covered with a dense oxide film. The coating layer is applied by various methods: short-term immersion in a bath of molten metal (hot coating), electrodeposition from aqueous electrolyte solutions (galvanic coating), spraying (metallization), processing with powders at elevated temperatures in a special drum (diffusion coating), using a gas-phase reaction , for example 3 Cr. Cl 2 + 2 Fe - → 2 Fe. Cl 3 + 3 Cr (in an alloy with Fe).

There are other methods for applying metal coatings, for example, a kind of diffusion method for protecting metals is immersing products in a melt of calcium chloride Ca. Cl 2, in which the deposited metals are dissolved.

Atmospheric corrosion of steel The most common type of steel corrosion in practice is the formation of rust under the influence of atmospheric influences (most often oxygen and humidity). In dry atmospheric air, steel practically does not corrode. Atmospheric corrosion is electrochemical in nature, and the electrolyte is a layer of moisture present on the surface of the metal.

The course of corrosion processes in atmospheric conditions is similar to the corrosion of steel in water containing oxygen. Corrosion products covering the metal are hydrated iron oxides with a composition determined by the formula The rate of atmospheric corrosion depends on the moisture content in the air. Increasing the relative humidity of the air to 70 -75% leads to relatively small losses of steel. At humidity exceeding these values, intensive acceleration of corrosion processes is observed. Air pollution with aggressive products such as CO 2, SO 2, CI 2, H 2 S, smoke and soot increases corrosion. Steel that has been exposed to an industrial atmosphere for several years has significantly greater losses than steel in rural areas.

Inhibitors The use of inhibitors is one of the effective ways to combat metal corrosion in various aggressive environments (atmospheric, in sea water, in coolants and salt solutions, under oxidizing conditions, etc.). Inhibitors are substances capable of slowing down or stopping chemical processes in small quantities. The name inhibitor comes from lat. inhibere, which means to restrain, stop. Inhibitors interact with intermediate products of the reaction or with active sites on which chemical transformations occur. They are very specific for each group of chemical reactions. Corrosion of metals is just one of the types of chemical reactions that are amenable to the action of inhibitors. According to modern concepts, the protective effect of inhibitors is associated with their adsorption on the surface of metals and inhibition of anodic and cathodic processes.

The first inhibitors were found by chance, by experience, and often became a clan secret. It is known that Damascus craftsmen used solutions of sulfuric acid with the addition of brewer's yeast, flour, and starch to remove scale and rust. These impurities were among the first inhibitors. They did not allow the acid to act on the weapon metal, as a result of which only scale and rust were dissolved.

According to 1980 data, the number of corrosion inhibitors known to science exceeded 5,000. It is believed that 1 ton of inhibitor saves about 5,000 rubles in the national economy. Corrosion control is of great national economic importance. This is a very fertile area for the application of strength and abilities.

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Presentation - Corrosion of metals and methods of protection against corrosion

The text of this presentation

Chemistry lesson on the topic "Corrosion of metals and methods of protection against corrosion"
Prepared by the teacher of chemistry of the secondary school of the State Enterprise "Republican Rehabilitation Center for Children and Adolescents" Lepesbayeva Sandugash Kairatovna

Lesson Objectives:
to form students' understanding of the mechanism of corrosion processes, their consequences and methods of protection against corrosion; develop the ability to work with a reference summary, observe, draw conclusions; educate an emotional attitude to the phenomenon being studied.

Cast iron
Alloy of iron with carbon (2-4%)
Steel
Alloy of iron with carbon (less than 2%)
Used in mold casting
By adding alloying elements improves the quality

In the III BC, a lighthouse was built on the island of Rhodes in the form of a huge statue of Helios. The Colossus of Rhodes was considered one of the seven wonders of the world, but it lasted only 66 years and collapsed during an earthquake. At the Colossus of Rhodes, the bronze shell was mounted on an iron frame. Under the influence of humid, salt-saturated Mediterranean air, the iron frame collapsed.

What is the symbol of Paris? - Eiffel Tower. She is incurably ill, rusts and collapses, and only constant chemotherapy helps to fight this deadly disease: she was painted 18 times, which is why her weight of 9000 tons increases by 70 tons each time.

Corrosion - a red rat, Gnawing on scrap metal. V. Shefner
Every year, up to ¼ of the produced iron is “lost” in the world ...

A.N. Nesmeyanov
To know is to win!

Journey through the realm of the "Red Devil"
Art. Informational
Art. experimental
Art. Practical

destruction of metals and alloys under the influence of the environment.
Corrosion

Types of corrosion
By the nature of the destruction, continuous (general): uniform, uneven local (local): point, spots, ulcers, subsurface, through, etc.

Types of corrosion
solid dotted

Ulcerative intergranular

Chemical corrosion
- the metal is destroyed as a result of its chemical interaction with an aggressive environment (dry gases, non-electrolyte liquids).
Formation of scale during the interaction of iron-based materials at high temperature with oxygen: 8ē 3Fe0 + 2O20 → (Fe+2Fe2+3)O4-2
Video fragment
Laboratory experience - glowing copper wire

Electrochemical corrosion
- in the electrolyte environment, an electric current arises when two metals come into contact (or on the surface of one metal having an inhomogeneous structure); - corrosion resembles the work of a galvanic cell: electrons are transferred from one part of the metal to another (from metal to inclusion).
Video fragment

The Fe2+ ions formed at the anode are oxidized to Fe3+: 4Fe2+ (aq) + O2 (g) + (2n + 4)H2O (l) = 2Fe2O3 nH2O (solid) + 8H+ (aq)
Corrosion of metal in humid air

Iron slightly corroded in water; in pure water, corrosion proceeds more slowly, since water is a weak electrolyte.
Let's compare the results of experiments No. 2 and No. 5

The addition of NaCl to water enhances the corrosion of Fe. the addition to the NaCl-NaOH solution, as can be seen from experience, on the contrary, weakened the corrosion, there was little rust.
Let's compare the results of experiments No. 1 and No. 2

That. The corrosion rate of a given metal depends on the composition of the surrounding medium. Some components of the metal-washing medium, in particular Cl- - ions, enhance the corrosion of metals, other components can weaken corrosion. Corrosion of Fe is weakened in the presence of OH- - ions.

In both cases, Fe is in the same solution, but in one case it is in contact with zinc, while in the other it is not. In test tube No. 2, the brown precipitate is rust, and in test tube No. 4, the white precipitate is Zn (OH) 2 it comes into contact with zinc.
Let's compare the results of experiments No. 2 and No. 4

Zn is oxidized as a more active metal
BUT (-)
split off from its atoms
move to the surface of Fe and restore
K(+)Fe

In both cases, Fe is in the same solution, but in one case it is in contact with copper, while in the other it is not. Corrosion occurred in both test tubes and a brown rust precipitate appeared. There was less rust in test tube No. 2 than in test tube No. 3. Conclusion: Thus, the corrosion and rusting of iron is greatly enhanced when it comes into contact with copper.
Let's compare the results of experiments No. 2 and No. 3

BUT (-)
K(+)Cu
The reaction of oxygen dissolved in water with iron leads to the formation of brown rust.

The corrosion of a metal increases sharply if it comes into contact with some other, less active metal, i.e., located in the electrochemical series of metal voltages to the right of it. But corrosion slows down if the metal comes into contact with another metal located to the left in the electrochemical series of metal voltages, i.e., more active.

Corrosion protection
- Isolation of the metal from the environment - - Changing the environment

barrier protection
- mechanical isolation of the surface when using surface protective coatings: non-metallic (varnishes, paints, lubricants, enamels, gumming (rubber), polymers); metal (Zn, Sn, Al, Cr, Ni, Ag, Au, etc.); chemical (passivation with concentrated nitric acid, oxidization, carburization, etc.)

barrier protection

What surface protective coating was used in this case? Which group of surface protective coatings does it belong to?
Video fragment
barrier protection

Change in the composition of the metal (alloy)
Protective protection - the addition of powder metals to the coating material, which create donor electron pairs with the metal; creating contact with a more active metal (for steel - zinc, magnesium, aluminum).
Under the action of an aggressive environment, the powder of the additive gradually dissolves, and the base material does not corrode.

Rivets or plates of a more active metal are attached to the main structure, which are subject to destruction. Such protection is used in underwater and underground structures.

The passage of an electric current in the opposite direction to that which occurs during the corrosion process.
Change in the composition of the metal (alloy)
electrical protection

In everyday life, a person most often encounters iron coatings with zinc and tin. Sheet iron coated with zinc is called galvanized iron, and plated with tin is called tinplate. The first is used in large quantities on the roofs of houses, and tin cans are made from the second.
Change in the composition of the metal (alloy)
Video fragment

Introduction of alloying additives into the metal: Cr, Ni, Ti, Mn, Mo, V, W, etc.
Change in the composition of the metal (alloy)
alloying

Changing the environment
inhibition
The introduction of substances that slow down corrosion (inhibitors): - for acid corrosion: nitrogen-containing organic bases, aldehydes, proteins, sulfur-containing organic substances; - in a neutral environment: soluble phosphates (Na3PO4), dichromates (K2Cr2O7), soda (Na2CO3), silicates (Na2SiO3); - at atmospheric corrosion: amines, nitrates and carbonates of amines, esters of carboxylic acids.

In which test tube did the nail not rust and why?
Changing the environment

Changing the environment
Deaeration - removal of substances that cause corrosion: water heating; passing water through iron shavings; chemical removal of oxygen (for example, 2Na2SO3 + O2 → 2Na2SO4).

Think and explain (homework)
1. A plate of Zn and a plate of Zn, partially covered with Cu, were placed in a solution of hydrochloric (hydrochloric) acid. In which case is the corrosion process more intense? Motivate your answer by making electronic equations of the corresponding processes.
2. How does the atmospheric corrosion of nickel-plated iron proceed if the coating is broken? Compose the electronic equations of the anode and cathode processes.

1. I worked at the lesson 2. I worked with my work at the lesson 3. The lesson seemed to me 4. My mood 6. The material of the lesson was actively / passively satisfied / dissatisfied with the short / long became better / became worse understandable / not understandable useful / useless interesting / boring
Reflection

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