rail corrosion
Corrosion and Protective Measures for Rail Transit Rails
The particularity of urban rail transit makes it different from the ordinary railway system. The influencing factors of rail corrosion in urban rail transit are more complex, mainly affected by stray current, environmental humidity, temperature and pollutants in the atmosphere. In the presence of moist air, salt ions, rain and stray current, serious corrosion will occur on the contact surface between rail and rail bottom plate, as well as rail components, which will rapidly reduce the service life of rail.
1. The damage effect of stray current on steel
Because the urban rail transit basically adopts the direct current traction system, and the running rail is the return line, and the current used by the train is not stable, it is easy to leak into the track bed and the surrounding taxi soil media through the poorly insulated position of the track and the ground to form stray current. When stray currents flow in soil, metals such as gold sheath in the ground can be used as conductors. The current causes corrosion in the outflow of metal conductors to the surrounding soil, and also causes corrosion in the outflow of steel rails and nearby underground structures, metal pipelines, etc.
The stray current will cause the misoperation of the rail limit device and the potential rise of the running track for unknown reasons. The rail of the subway operating system and some accessories of the rail have very serious corrosion, which is in the place where the spike is driven into the track bed, it is difficult to achieve good insulation, these places are often the site of stray current corrosion.
2. The destructive effect of environmental media on steel
The corrosion of steel by environmental media is mainly caused by the electrochemical changes of metal materials in the atmosphere by the action of water and oxygen. The main influencing factors are climate conditions and pollution substances. When the locomotive passes through, the temperature and humidity of the rail members and the rail itself are increased, and the rise of the rail temperature lags behind the rise of the temperature, so that the water steam will condense on the rail surface, causing serious corrosion of the rail members.
The components and electrical connections on the rail are also subject to the chemical effects of corrosive media. This increases the possibility of rail electrical joints and components fracture, just because when the corrosive medium enters the electrical connection, the internal corrosion of the connection will form a hole, and the stress concentration will occur at the hole, even if the applied load itself has not reached the load value required to produce cracks, cracks can also occur from the corrosion hole. At the same time, the joint action of thousands of mechanical wear and chemical reaction accelerates the damage of the gasket in the rail tread and the spring bar fastener.
3. Rail transit steel corrosion protection measures
The corrosion of rail will not only cause huge economic losses, but also bring huge security risks to the operation system. Therefore, the corrosion protection of rail has been paid great attention.
(1) Control the source of stray current, apply conductive paste at the contact of the two conductors to reduce contact resistance and control the generation of stray current; The generated stray current can be reduced by drainage or other methods. The electric connection is coated with conductive paste to reduce the internal resistance of the reflux track and play the role of anti-oxidation and anti-corrosion; The important metal components along the rail are coated with protective layer, and the appropriate anti-corrosion treatment with conductive paste can effectively avoid the occurrence of corrosion.
(2) Improve environmental conditions and reduce the impact of corrosive media; coating with power compound grease is effective in preventing rust and corrosion of rail joints, bolts, and load-bearing cables.
Change the surface of the rail section to enhance anti-corrosion capabilities. For example, using hot-dip forged zinc and then applying two coats of asphalt anti-rust primer and two coats of asphalt aluminum powder topcoat after phosphating and passivation treatment is very effective in protecting columns and shoulder frames.
For bolt fasteners, they are coated with power compound grease, which does not change the size of the parts and achieves good corrosion resistance. The concrete sleeper bolts use anti-corrosion grease and the effect is good.
Apply protective layers to important metal components along the rails, and provide appropriate anti-corrosion treatment to the rails, which can effectively avoid corrosion.
