Under what circumstances will carbon steel be corroded and under what circumstances will corrosion b

Generally, it will be seriously corroded in some acid and alkali environments, and it will also be seriously corroded in some humid environments.

Metal external factors.

1.Effect of relative temperature.

Relative humidity in the air.

The higher it is, the thicker the water film on the metal surface, and the oxygen in the air passes through the water film to the metal surface. When the relative humidity reaches a certain value, the corrosion rate rises significantly, and this value is called the critical relative humidity, which is about 70% for steel.

2.The effect of temperature.

The ambient temperature is correlated with the relative humidity, and in a dry environment (desert), no matter how high the temperature is, the metal is not easy to corrode. When the relative humidity reaches a critical value, the effect of temperature is significantly intensified, and the corrosion rate increases by a factor of two for every 10 increase in temperature. Therefore, in the damp heat.

In the rainy season, the higher the temperature, the more severe the corrosion.

3.Effects of oxygen.

The rusting process is represented by the following reaction formula:

fe+h2o→fe（oh）2

fe（oh）2+ h2o+o2→fe（oh）3

fe+ h2o+o2→fe（oh）3

It can be seen that without water and oxygen, the metal will not rust, and 20% of the volume in the air is oxygen, which is pervasive.

4.Effects of other substances in the atmosphere.

The atmosphere contains salt spray and sulfur dioxide.

Hydrogen sulfide and dust will accelerate corrosion, therefore, the difference in the size of corrosion in different environments is obvious, and the urban area is higher than the rural area; The industrial area is higher than the living area; The coast is higher than the inland; High dust is higher than low dust.

Summary. Carbon steel can corrode stainless steel through electrolysis, especially in humid or high-temperature environments. The iron contained in carbon steel dissolves quickly and forms oxides and water molecules, creating an acidic environment that causes corrosion on the surface of stainless steel.

In addition, during the contact between the two, the metal ions of the carbon steel will be transferred to the surface of the stainless steel through the electrolyte, causing corrosion. Therefore, when using stainless steel, contact with other metals should be avoided as much as possible to reduce the risk of corrosion.

Carbon steel can corrode stainless steel through electrolysis, especially in humid or high-temperature environments. The iron contained in carbon steel dissolves quickly and forms oxides and water molecules, creating an acidic environment that causes corrosion on the surface of stainless steel. In addition, during the contact between the two, the metal ions of the carbon steel will be transferred to the surface of the stainless steel through the electrolyte, causing corrosion.

Therefore, when using stainless steel, we should avoid contact with other metals as much as possible to reduce the risk of corrosion and collapse.

I'm sorry I don't understand, but can you elaborate on that?

Carbon steel can corrode stainless steel through electrolysis, especially in humid or high-temperature environments. The iron contained in carbon steel dissolves quickly and forms oxides and water molecules, creating an acidic environment that causes corrosion on the surface of stainless steel. In addition, during the contact between the two, the metal ions of the carbon steel will be transferred to the surface of the stainless steel through the electrolyte, causing corrosion.

Therefore, when using stainless steel, we should avoid contact with other metals as much as possible to reduce the risk of corrosion and collapse.

Chromium (CR): In structural and tool steels, chromium significantly increases strength, hardness, and wear resistance, but reduces plasticity and toughness. Chromium can also improve the oxidation resistance and corrosion resistance of steel, so it is an important alloying element for stainless steel and heat-resistant steel.

Molybdenum (Mo): Molybdenum can refine the grain of steel, improve hardenability and thermal strength, and maintain sufficient strength and creep resistance at high temperatures (long-term stress at high temperatures and deformation.

Carbon steel is an example of a mixture that is mainly composed of carbon and iron. The hardness of carbon is higher, while the hardness of iron is lower, and it shows a certain hardness after mixing, and the higher the carbon content, the higher the hardness; The higher the carbon content, the lower the hardness. The hydrogen ions in the acid can corrode the iron in it, turning it into iron ions, which can dissolve.

Alkali has little effect on iron. The strong oxidation of strong acids can passivate carbon steel to form a dense oxide layer, while weak acids can directly corrode. The strength of the base has no effect on iron.

Both acids and alkalis can cause corrosion to carbon steel. But it has a lot to do with temperature!

Oxidizing strong acids (sulfuric acid) will form a passivation film on the surface of carbon steel, but only when the temperature is not high, and it is closely related to the flow rate! High flow rates wash away the protective layer. Reducing strong acids (hydrochloric acid) do not form passivation films.

Weak acid (HAC) is also corrosive, so it is generally recommended to use 316L at room temperature, and if the high temperature is above 120 degrees Celsius or contains trace halogen ions.

The corrosiveness of the lye is also related to the concentration and temperature, below 80 degrees with heat-treated carbon steel can barely be used, and if the high temperature and high concentration are not even stainless steel and TI, nickel-based Monel or incoloy should be used

The corrosion mechanism of the acid is different according to the understanding of the acid, the oxidizing acid and the reducing acid are different, and the concentration and temperature are also different.

The corrosion mechanism of strong and weak alkalis is similar.

The principle of corrosion resistance of all materials can be explained by the passivation film theory.