Laser Cleaning Removes Rust & Improves Oxidation Resistance
Nov 24, 2023
Laser rust removal uses laser to ablate rust, and the rust instantly heats up and vaporizes to achieve the purpose of rust removal. Compared with the traditional rust removal process, laser rust removal can not only remove rust, but also "incidentally" improve material properties, such as improving oxidation resistance, hardness, roughness, passivation, etc., as long as the laser parameters are set enough With precision, this specific purpose can be achieved.
In laser rust removal, laser energy density is a very important parameter. The higher the laser energy density, the higher the temperature reached instantly. As the laser energy density increases, the value that just reaches the level of rust removal is called the cleaning threshold. The value that just reaches the level of rust removal is called the cleaning threshold. The value that damages the base metal is called the damage threshold. In laser cleaning operations, the laser energy density must be greater than the cleaning threshold and less than the damage threshold, so that rust can be removed without damaging the base metal. The optimal value is 80% of the damage threshold, which can achieve the best rust removal effect and the highest rust removal efficiency. If you want to improve other properties of metal materials, the laser energy density needs to be between 0.8 times and 1.2 times the damage threshold.
The melting point of carbon steel is 1470 degrees. When it reaches 1300 degrees, the surface of carbon steel will lattice and form a dense oxide layer. It is a uniform, small-thick, cellular dendritic structure "plating" , can improve the corrosion resistance and oxidation resistance of carbon steel surfaces, which is very important in actual industrial production. It can effectively protect the metal matrix, reduce the rust rate, and improve the mechanical properties at the same time.
We have done an experiment, using a 100-watt laser cleaning machine to remove oxides from the surface of aluminum alloys and improve the oxidation resistance of the metal. The laser spot diameter is 70um, and the laser energy density is 1.1 times the damage threshold. After the experimental operation, SEM was used to observe the condition after rust removal, and it was found that micro-nano structures were generated on the surface. This structure has a certain impact on the hydrophobicity, roughness, and light absorption rate of the material. Compared with the original material:
1. The hydrophobicity decreases, and under different parameters, the hydrophobicity changes greatly.
2. Improved mechanical properties and improved compressive deformation resistance.
3. Increased roughness. By setting the laser parameters, we can get the roughness we want, and it is found that the roughness of the metal surface is closely related to the scanning speed. The faster the scanning speed, the lower the roughness.
4. The light absorption rate is greatly increased because the metal surface loses its metallic luster, reduces the light reflected on the metal surface, and absorbs more light.
Rust is a layer of porous structure. Moisture and oxygen will continuously penetrate into the substrate and cause further corrosion, leading to the "Matthew Effect" of corrosion. Corrosion will be accelerated in places with slight corrosion. After corrosion, the mechanical properties will be greatly reduced, which can easily cause accidents. If the anti-oxidation properties of the metal surface are improved and a layer of paint is added, the probability of rust can be greatly reduced. Compared with traditional sandblasting rust removal and chemical pickling rust removal, laser rust removal can not only remove rust, but also add a "protective coat" by the way. From the perspective of rust removal efficiency, laser rust removal can now reach a maximum of 60 square meters/hour, which is similar to the efficiency of sandblasting rust removal, but is not high enough. In terms of cost, laser rust removal requires a one-time purchase of the machine, which costs more in the later stage. There are fewer consumables, and the cost of a single rust removal is about the same or even lower than that of sandblasting. There are no problems in environmental protection, and it is easy to realize robot automation. In large-area rust removal, calculate the environmental protection costs and labor costs. Laser removal The cost of rust has surpassed other rust removal methods.
