In the 1980s, automobile anti-corrosion technology did not get enough attention in China. With the continuous expansion of the automobile market and the increasingly fierce automobile competition, users have higher and higher requirements for body coating. Therefore, the manufacturer attaches great importance to the rust prevention of the car body, the fading, color matching and gloss of the coating, and pays special attention to it. The application of innovative anti-corrosion technology can not only improve the appearance quality of the car, but more importantly, it can also improve the internal quality of the car, prolong the service life of the car, improve the grade of the car, and even become a growth point driving product sales.

1 metal corrosion and hazards

The materials used in the manufacture of auto parts are mainly metal, and the corrosion of metal materials in use is difficult to avoid. When metal parts are in corrosive gas or liquid environment, chemical corrosion or electrochemical corrosion occurs on the surface to form a corrosive layer. Friction will peel them off and cause damage to parts. This phenomenon is corrosive wear.

In addition to the sulfur content in the fuel, the wear degree of automobile engine mainly depends on the cooling degree of cylinder. The lower the engine temperature is, the more acidic substances are easy to form on the cylinder wall and the stronger the corrosion effect is; When the temperature rises, these acidic substances are discharged with the waste gas in a vapor state, and the corrosion is much smaller; However, when the temperature is too high, the viscosity of lubricating oil becomes low, the oil film is not easy to form, the anti-corrosion effect is reduced, and the wear is intensified.

The corrosion of vehicle metal parts will not only reduce its quality and service life, but also the parts damaged due to its corrosion are very easy to cause traffic accidents, and even cause the tragedy of vehicle destruction and death. With the increase of the service life or mileage of the vehicle, the corrosion of mechanical parts in various parts gradually intensifies. The common parts with serious corrosion are sheet metal parts, such as cab, trunk, bus shell, bottom plate, fender, front (fender, mask), etc. These parts are often in contact with sediment, gravel and water. For example, when the wheel splashes gravel and sediment hit the protective layer on the vehicle surface, it is very easy to scratch the paint layer, destroy its integrity and continuity, and expose the metal. When it comes into contact with oxygen in water and air, it will play a chemical role and produce corrosion.

2 main factors affecting vehicle corrosion

The main factors causing vehicle corrosion are service environment and its own structure. The automobile service environment is relatively harsh and changeable, resulting in corrosion damage of automobile parts.

Influence of moisture: sediment, dirt and moisture accumulated under the vehicle body will accelerate corrosion;

Influence of humidity: in areas with high relative humidity (such as coastal areas), corrosion will accelerate;

Effect of temperature: when the temperature rises, the parts at the place with poor ventilation will accelerate corrosion.

Dirt or debris containing moisture accumulate in the body panel, air or other parts; Corrosive environment generated inside the vehicle, such as high temperature generated by the engine, combustion waste gas containing sulfur and chloride ions, acid mist and liquid leakage generated by the battery; The stress caused by vibration and impact during work, and the local damage caused by friction and collision are also the main reasons for the corrosion damage of auto parts.

3 mechanism of metal corrosion

The change process of metal corrosion usually starts from the surface, and then gradually erodes to the inner layer, resulting in irreparable losses. First, the appearance loses luster, making the smooth surface rough and covered with a layer of metal oxide, that is, metal corrosion products. If iron is covered with a layer of brown rust due to corrosion, it is rust composed of iron oxides.

The main mechanism of metal corrosion is that the raw metal is transformed into metal oxide, resulting in rust, damage or even scrapping of structural parts or components. The aging of non-metallic materials such as paint, rubber and FRP fiber is mainly due to the physical and chemical changes such as cracking, degradation and dissolution of the polymer structure of the material after the comprehensive effect of the environment, resulting in the decline of appearance and performance.

When there are oxygen and acidic substances between the friction surfaces of metal parts, chemical corrosion will occur, which will make the surface locally corroded and continuously expand and extend, resulting in granular spalling, change the surface shape of parts and cause early wear. It can be seen that the design structure, applied materials, technology and protective measures of the automobile directly determine its corrosion resistance.