Why does iron rust fast in salt water?

Iron rusts quickly in salt water because sodium chloride is an electrolyte that forms a galvanic cell with iron, which accelerates the corrosion of iron, and in simple terms, the chloride ion concentration in the brine is enhanced, acidic, which destroys the passivation film of iron and promotes iron corrosion.

Because galvanic cells are formed.

Galvanic cells can dramatically speed up the reaction rate, similar to the role of a catalyst (I didn't say equivalent to a catalyst).

Now I'm number four. To add.

Oxygen is on the surface of the NaCl solution, while Fe is in the solution. At this time, the electrons in Fe will run through the solution to the oxygen.

The distribution reaction formula of galvanic cells is.

Negative electrode: Fe-2E(-)Fe(2+).

Positive electrode: 2h(+)2e(-)h2

The reaction formula is Fe+2H2O=Fe(OH)2+H2, and Fe(Oh)2 is oxidized by oxygen in the air to form iron hydroxide 4Fe(OH)2+O2+2H2O=4Fe(OH)3, so that rust is produced on the surface of steel. In the above corrosion process, hydrogen gas is released, which is called hydrogen evolution corrosion.

What about the students in the first year of junior high school, you don't need to memorize these formulas, the content of the second year of high school, hehe.

Because the brine is an electrolyte solution, iron forms a galvanic battery in the salt solution, and oxygen absorption corrosion occurs, in which iron is the negative electrode, the impurities in the iron are the positive electrode, and the salt solution is the electrolyte solution.

Why is iron more likely to rust in salt water, because salt is NACI will oxidize the iron oxide outside the iron, so it will be easier to rust.

If the water contains salt, then it becomes an electrolyte, and iron rusts easily under the action of the electrolyte. Therefore, if the iron we use is encountered with salt water, it will quickly corrode.

Because iron is a metal that oxidizes easily, it is prone to rust.

The galvanic cell reacts, and the ions are conductive because the two metals are usually two with different activities, taking iron and copper as an example, because there is moisture in the air, the water usually contains acidic gases, such as carbon dioxide, iron encounters acid and loses electrons to become ferrous ions, and the electrons move to copper through the metal, and then reduce to hydrogen to form a galvanic cell.

This is a typical example of galvanic corrosion. A thin layer of water film will be formed on the surface of steel in humid air, and the water film will dissolve carbon dioxide, sulfur dioxide, hydrogen sulfide, and other gases from the atmosphere, so that the water film contains a certain amount of hydrogen ions, and as a result, a thin film of electrolyte solution is formed on the surface of steel, which forms a galvanic battery with iron and a small amount of carbon in steel. Because hydrogen is continuously released during the corrosion process, it is called hydrogen evolution corrosion, which is corrosion caused in an acidic environment.

Under normal circumstances, if the water film adsorbed on the surface of steel is very acidic or neutral, but there is a certain amount of oxygen dissolved, oxygen absorption corrosion will occur at this time. In these two electrochemical corrosion processes, if there are salts in them, they will speed up the movement of electrons in the solution and play a role in conducting electricity, which can speed up the corrosion rate of steel.

Salt water can speed up the rust of iron, mainly because salt water contains oxygen, which can attack iron. Rust is particularly easy to absorb water, so that the iron rusts faster, but the rust is not very hard, and it is often easier to fall off, and generally the volume of iron will be several times larger than the original after rusting.

Salt water will speed up the cause of iron rusting

Salt water can speed up the rusting of iron, mainly because it contains oxygen. If only water will not make iron rust, mainly because the oxygen in the air dissolves in the water, a chemical reaction will occur to form iron oxide, which is commonly known as rust.

The chemical properties of iron are very lively, it is easy to rust and has a great connection with the outside world, moisture can easily make iron rust, and rust is particularly easy to absorb moisture, so if the rust is not removed as soon as possible, the iron will rust faster. In addition, iron rusts faster in acid-base solutions.

Rust is usually brownish-red, and it is not as hard as iron. After the iron rusts, it becomes several times larger in size. If a piece of iron is completely rusted, it will be 8 times larger than it was before, and after the iron rusts, it will become heavier, 3 to 5 times heavier.

The role of salt water is to accelerate the process of rust formation.

Because the chloride ions in the brine are oxidized with iron, the active metal genus is easy to be corroded, so the iron surface corrosion in the brine will be faster than that of water, and the water cannot react directly with the iron and should be heated at high temperature, so the rate of iron corrosion in water is slower than that of the brine.

Because galvanic cells are formed.

The galvanic cell can greatly speed up the reaction rate, similar to the role of a catalyst (I didn't say the same as a back catalyst) A.

Oxygen is on the surface of the NaCl solution, while Fe is in the solution. At this time, the electrons in Fe will run through the solution to the oxygen.

The distribution reaction formula of galvanic cells is.

Negative electrode: Fe-2E(-)Fe(2+).

Positive electrode: 2h(+)2e(-)h2

The reaction formula is Fe+2H2O=Fe(OH)2+H2, and Fe(Oh)2 is oxidized by oxygen in the air to form iron hydroxide 4Fe(OH)2+O2+2H2O=4Fe(OH)3, so that rust is produced on the surface of steel. In the above corrosion process, hydrogen gas is released, which is called hydrogen evolution corrosion.

Salt water accelerates the corrosion of iron. The results show that the corrosion of iron is not only related to air and water, but also related to chloride ions in water, and the salt in water increases the conductivity of the electrochemical electrolyte and promotes the electrochemical reaction.

Salt can cause iron to corrode faster because salt and iron form galvanic cells, and this electrochemical corrosion is faster than normal rust.

The reaction equation is:

Negative Reaction Formula (Fe): 2Fe - 4e = 2Fe

Positive reaction formula (c): o +4e +4h o = 4oh

Iron will form a thin layer of water film on the surface of moist air, and the water film will dissolve carbon dioxide, sulfur dioxide, hydrogen sulfide, and other gases from the atmosphere, so that the water film contains a certain amount of hydrogen ions, which makes a thin film of electrolyte solution formed on the surface of iron, which just forms a galvanic battery with iron and a small amount of carbon in the iron.

When the metal is placed in an aqueous solution or a humid atmosphere, a kind of micro-battery will be formed on the surface of the metal, also known as a corrosive battery (its electrodes are customarily called cathodes and anodes, not positive and negative electrodes). An oxidation reaction occurs on the anode, which dissolves the anode and a reduction reaction occurs on the cathode, which generally only plays the role of transferring electrons.

The reason for the formation of corrosive batteries is mainly due to the adsorption of moisture in the air on the metal surface to form a layer of water film, so that CO, SO, NO, etc. in the air are dissolved in this layer of water film to form an electrolyte solution, and the metal soaked in this layer of solution is always impure.

For example, industrial steel is actually an alloy, that is, in addition to iron, it also contains graphite, cementite, and other metals and impurities, most of which are not as active as iron. In this way, the anode of the corroded battery is iron, and the cathode is impurity, and because the iron is in close contact with the impurities, the corrosion is continuous.

Stainless steel can also rust under certain conditions. The size of its corrosion resistance changes with the chemical composition of the steel itself, the state of the additive, the use conditions and the type of environmental medium. When acid, alkali and salt (such as alkaline water, lime, etc.) are attached to the surface of stainless steel, it is very easy to cause local corrosion, so salt water can make stainless steel rust.

Stainless steel is a layer of extremely thin and strong and fine stable chromium-rich oxide film (protective film) formed on its surface to prevent the continued penetration and oxidation of oxygen atoms, and obtain the ability to resist corrosion.

Once for some reason, the film is constantly damaged, the oxygen atoms in the air or liquid will continue to seep in or the iron atoms in the metal will continue to precipitate out, forming loose iron oxide, and the metal surface will be constantly corroded.

The reason why salt water can speed up the rust of iron is that there is oxygen in salt water that can attack iron.

Iron is susceptible to rust, not only because of its chemical activity, but also because of external conditions. Moisture is one of the substances that makes iron rust easily.

However, only water does not rust iron, only when the oxygen in the air is dissolved in the water, the oxygen reacts with iron in the presence of water to form iron oxide things, which is rust, and iron rusts faster in moist air in the presence of a solution of acid, alkali or salt.

If the rust is not removed, the spongy rust is particularly easy to absorb water, and the iron will rust faster, and the iron will be heavier when it rusts, about 3 to 5 times its original weight.