What are the main factors that affect metal rust and what are the main factors that cause metal rust

1 Influence of relative temperature The higher the relative humidity in the air, the thicker the water film on the metal surface, and the oxygen in the air acts 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 influence of temperature The ambient temperature is related to 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 humid tropics or rainy season, the higher the temperature, the more severe the corrosion.

3 Effect 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 Influence of other substances in the atmosphere When the atmosphere contains salt spray, sulfur dioxide, hydrogen sulfide and dust, it will accelerate corrosion, so the difference in the size of corrosion in different environments is obvious, and urban areas are higher than rural areas; The industrial area is higher than the living area; The coast is higher than the inland; High dust is higher than low dust.

Rust factors during processing.

The raw material has been corroded and cannot be removed after processing; Cutting fluids, lubricants and other process materials are in contact during processing; improper neutralization and cleaning after pickling; Heat treatment, oxidation, decarburization or residual salt cleaning is not clean; Sweaty hands left by the operator during inspection, handling and assembly; improper stress relief or dehydrogenation annealing; It is not suitable for rust prevention between processes and sealing.

The main factors that cause metal rust: water and oxygen.

Causes of metal rusting: mainly electrochemical corrosion.

and air oxidation, pure or active metals are mainly due to the oxidation reaction between the metal surface and the oxygen in the air.

As a result, metal oxides are formed on the surface of the metal.

Rust appears. If the metal contains more impurities, the impurities will form a chemical galvanic cell with the metal, and electrochemical corrosion will occur, thereby oxidizing the metal to form metal oxides.

Please click Enter a description.

Iron rusts because it reacts with oxygen and water in moist air, related to oxygen and water. If you have both at the same time, it is easy to rust. Rust is a chemical reaction.

It is essentially an oxidation reaction of a metal. The most common phenomenon of rust is the oxidation of iron products with oxygen after long-term exposure to air, or oxygen in water.

Erosion becomes oxide.

Please click Enter a description.

(1) Relative humidity of the atmosphere

The percentage of the water vapor content of the atmosphere to its water vapor saturation content at the same temperature is called the relative humidity. The rate of metal corrosion is small below a certain relative humidity, and increases dramatically above this relative humidity. This relative humidity is called critical humidity.

The critical humidity of many metals is between 50% and 80%, and the critical humidity of steel is about 75%. Atmospheric relative humidity has the greatest effect on metal corrosion. When the atmospheric humidity is higher than the critical humidity, water film or water beads appear on the metal surface, if the harmful impurities contained in the atmosphere are dissolved in the water film and water droplets, it will become an electrolyte and aggravate corrosion.

(2) Temperature and humidity

The correlation between atmospheric temperature and humidity affects metal corrosion. This has the following main conditions: first, the water vapor content of the atmosphere increases with the increase in temperature; Second, high temperatures increase corrosion, especially in humid environments, where the higher the temperature, the faster the corrosion will be.

When the relative humidity is low, the effect of temperature on rust is not obvious, but when the relative humidity is higher than the critical humidity, the amount of rust increases sharply with the increase of temperature. In addition, if there is a temperature difference between the atmosphere and the metal, condensation will form on the surface of the metal at low temperature, which will also cause the metal to rust.

(3) Corrosive gases

Sulfur dioxide has the greatest impact on metal corrosion, especially for steel, copper and their alloys. Sulfur dioxide in the atmosphere is mainly used in the combustion of coal. At the same time, the combustion product carbon dioxide also has a corrosive effect.

Corrosive gases are mixed in the atmosphere around the plant. For example, hydrogen sulfide, ammonia, hydrochloric acid gas, etc. are all factors that promote metal corrosion.

Of course, it is self-evident that atmospheric oxygen is the most common for metal rust and that it can occur anytime and anywhere.

(4) Other factors

The atmosphere contains a large amount of dust, such as smoke, coal ash, chloride and other acids, alkalis, salt particles, etc., some of which are corrosive, or condensation nuclei of water droplets, which are also rust factors, such as chloride is considered to be the "sworn enemy" of corrosive metals.

The 3 main causes of metal rust.

Humidity: The critical humidity for many metals is between 50% and 80%, and about 75% for steel. If the ambient humidity is less than the critical humidity of the metal, the rate of oxidative corrosion of your gold will be much smaller, and conversely, it will accelerate the occurrence of metal rust.

Temperature: It is generally considered that a high-temperature corrosive environment is considered when the operating temperature of a metal reaches 30% to 40% of its melting point (absolute temperature). The higher the temperature, the higher the chance of metal corrosion.

Corrosion factors: Some metal processing processes will produce chlorides, sulfides and other corrosive gases, which are factors that directly accelerate the oxidation and rusting of metals.

The main cause of metal rust is chemical oxidation. For example, metallic iron, when exposed to oxygen in air or water, will be oxidized to ferric tetroxide, which will appear red. Over time, a layer of rusty rust forms on the surface of the iron, which is made up of ferric tetroxide.

There are many causes of metal rust, but the main factors are humidity, various elements such as acids and alkalis in the air, and corrosive liquids, which can cause metal rust and corrosion. To prevent metal rusting, painting can be done on the metal surface to effectively prevent metal rusting.

What are the main factors that cause metal rust? Dampness is the main cause of rust. Not commonly used.

1.Metal reactivity.

2.Environmental conductivity.

3.Exposure to oxygen.

The cause of metal rust is mainly the effect of electrochemical corrosion and air oxidation, and pure metal or active metal is mainly due to the oxidation reaction between the metal surface and the oxygen in the air, and the metal clean oxide is generated on the metal surface, that is, rust. If the metal contains more impurities, these impurities will form a chemical galvanic battery with the metal, and electrochemical corrosion will occur, thereby oxidizing the metal to form metal oxides.

Some metals, such as alumina, can rust and produce a dense oxide film that prevents further oxidation. However, the oxide film produced by some metals after rusting is sparse and the metal oxidation is faster, such as: iron is rusting.

The essence of metal corrosion is the process of metal atoms losing electrons and being oxidized, and metal corrosion can generally be divided into chemical corrosion and electrochemical corrosion. Galvanic corrosion is the most common and important type of metal corrosion. In fact, with the change of the environment, various factors affecting corrosion become more and more complex, which will change the degree or type of corrosion, and increase the severity of corrosion.

There are many factors that affect metal corrosion, and metal corrosion is caused by various internal and external factors, mainly the following:

1.ambient temperature and humidity;

In general, an increase in temperature accelerates the rate of chemical reactions. Therefore, the effect of temperature on chemical corrosion is more obvious.

2.the composition and pH of the solution in contact with the metal surface;

3.A variety of environmental media that come into contact with metal surfaces.

4.the chemical composition and structure of the metal material itself;

The more reactive the metal, the more likely it is to lose electrons and be corroded. If the impurities in the metal that can conduct electricity are not as active as the metal, it is easy to form galvanic cells and electrochemically corrode the metal.

5.metal surface finish (oxygen concentration difference, battery corrosion);

Metals are susceptible to corrosion when exposed to moist air, corrosive gases, and electrolyte solutions.

There is a chemical reaction with water and oxygen in the atmosphere! It is caused by the formation of iron oxides!!

Reacts with water, oxygen, etc. in the air.

Oxidation with air becomes rust.

Metals themselves often combine with stable elements such as water, carbon dioxide, and oxygen to form a compound state, which is called metallic growth"Rust"Finish.