Main Factors Affecting the Corrosion of Screw Spikes for Railway

(I) The influence of the relative humidity of the atmosphere
Relative humidity indicates the humidity of the atmosphere. Generally speaking, the higher the relative humidity, the more likely it is to form a water film on the surface of the railroad screw spike, and the longer the water film will be maintained, so atmospheric corrosion is more likely to occur.

(2) The influence of temperature and temperature changes
In general, as the temperature increases, the reaction speed of the anode and the anode can be accelerated, which accelerates atmospheric corrosion. If the temperature rises enough to dry the water film, the atmospheric corrosion rate may also be reduced.
Temperature changes, that is, the existence of temperature differences, have a greater impact on atmospheric corrosion, because the existence of temperature differences will promote the condensation of water vapor on the iron surface to form a water film, forming conditions for atmospheric corrosion. For example, because the road stud is in an outdoor environment, the temperature changes of day, night, cold and heat may cause water vapor to condense on the metal surface to form a water film, which accelerates corrosion.

(3) The influence of acid, alkali, salt and other gas pollution
If there is a small amount of H+ ions in the water film, its precipitation on the cathode can accelerate the cathode process; H+ ions can also destroy the passivation film on the surface of the iron metal, thus accelerating iron corrosion. OH- ions have little effect on the atmosphere of steel.
Salts are contained in the water film or on the surface of steel and metal, especially when Cl- ions are contained. Because Cl- ions have strong water absorption, they can increase the conductivity of the liquid film and can also destroy the oxide film or passivation film. The corrosion rate increases.
The most harmful gas pollution is SO2 or H2S. They can directly participate in the cathode reaction, accelerate the cathode reaction, and at the same time dissolve the passivation film on the surface of the iron metal, making the anode reaction easier to proceed, thereby accelerating the atmospheric corrosion rate.

(4) The influence of dust particles
The air often contains particles of sand, soot and coal ash, metal oxides and salts. In addition, when the train passes through, the dust particles will increase the existence of dust particles. These dust particles will accelerate the corrosion when they fall on the surface of the iron metal. This is because these particles can cause the core of capillary agglomeration and accelerate the formation of a water film; and some can absorb harmful gases such as SO2, which will accelerate the corrosion of iron metal. When the particles are relatively large, they will form crevices with the surface of iron metal, which will also cause crevice corrosion.