Rust removal principle
Corrosion occurs when metal is oxidized by substances such as oxygen and water vapor in the air. Once rust occurs, it will affect the metal
The workpiece is extremely damaged. The degree of rust will change from light to heavy with time. At the same time, the rust will spread from the surface of the workpiece to the inside of the workpiece until the entire workpiece is completely rusted. Therefore, rust removal is an important issue. Laser rust removal without chemicals and mechanical polishing
Laser rust is fast and safe, and it can derust various metal materials. High work efficiency, high degree of automation, simple process, no follow-up processing work, greatly improving work efficiency, reducing labor intensity of workers, saving production costs
The pulsed Nd:YAG laser cleaning process relies on the characteristics of the light pulses generated by the laser, based on the photophysical response caused by the interaction between the high-intensity beam, the short-pulse laser, and the contamination layer. The physical principle can be summarized as follows
The beam emitted by the laser needs to be absorbed by the contamination layer on the treated surface
Absorption of large energy forms a rapidly expanding plasma highly ionized unstable gas, generating shock waves.
The shock wave turns the contaminants into pieces and is rejected.
The width of the light pulse must be short enough to avoid heat build-up that destroys the treated surface.
Experiments have shown that when an oxide is present on a metal surface, plasma is generated on the metal surface
The plasma is generated only when the energy density is above the threshold, which depends on the contaminant layer or oxide layer removed. This threshold effect is very important for the effective cleaning of the base material. There is a second threshold for the appearance of plasma
If the energy density exceeds this threshold, the base material will be destroyed. In order to ensure effective cleaning of the substrate material, laser parameters must be adjusted according to the conditions so that the energy density of the light pulse is strictly between two thresholds.
Each laser pulse removes a certain thickness of the contamination layer. If the contamination layer is thick, multiple pulses are required for cleaning. The number of pulses needed to clean the surface depends on the degree of surface contamination. An important result produced by the two thresholds is the self-control of cleaning. Light pulses with an energy density above a first threshold will always remove contaminants until the substrate material is reached. However, because its energy density is lower than the damage threshold of the base material, the base is not damaged.
Laser cleaning can be used not only to clean organic contaminants, but also to clean inorganic materials, including metal corrosion, metal particles, and dust. It is now widely used.