How does laser cleaning technology work?

In this article, how laser cleaning technology works and why it is beneficial will be explored in the context of metal surface cleaning.

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What is laser cleaning technology?

Light amplification by stimulated emission of radiation (laser) is a monochromatic and coherent electromagnetic source that propagates in a straight line with negligible deviation. Currently, lasers are used in a variety of material processing applications in the manufacturing sector, from surface cleaning to nanofabrication.

Laser cleaning represents a non-destructive and non-contact cleaning method that allows the controlled removal of surface contaminants from the bulk of the material using a laser beam. Thus, laser cleaning machines are gradually becoming the tool of choice for containment removal processes/cleaning.

The appropriate laser type and optimal parameters are different for each cleaning application. Laser output parameters can vary greatly depending on the laser cleaning method. Thus, specific laser output parameters can be selected depending on the material/contaminant to be removed.

Steam cleaning and dry cleaning are the major types of laser cleaning methods used to remove surface contaminants. Dry laser cleaning involves pulsed laser heating of a dry solid surface, while steam laser cleaning involves pulsed laser heating of a solid surface in the presence of a liquid layer.

Dry laser cleaning turns into evaporative cleaning when the energy of the incident laser pulse is increased. Although the technique is simple, dry cleaning is less efficient than steam cleaning and requires higher laser intensity. Furthermore, dry laser cleaning can damage the metal surface.

How laser cleaning technology works

Laser cleaning is primarily a form of laser ablation that uses a laser beam to remove a layer of material or material deposited on a surface. Laser rust removal on steel and other materials is based on a laser ablation process.

However, laser ablation of a material only occurs when the energy of the incident laser beam exceeds the ablation threshold of that material. Each material has a specific dissociation threshold depending on its molecular bonds, and the threshold differs from other materials.

Therefore, a material can be ablated highly selectively during laser cleaning without affecting the other material when the difference between the ablation thresholds of the two materials is large enough.

For example, the separation threshold of rust is significantly lower than that of steel or aluminum, allowing the use of a laser cleaning machine to completely vaporize the rust without damaging the underlying steel.

Laser cleaning technology, laser cleaning, lasers

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Although both pulsed and continuous laser beam-based cleaning processes can be used to effectively remove the layer, the speed of the process depends on the laser beam used for cleaning.

A pulsed laser beam is more efficient and provides faster removal speed than a continuous laser beam. Additionally, the use of a pulsed laser beam can prevent overheating of the underlying metal.

Advantages and Disadvantages of Laser Cleaning Technology

Laser cleaning is environmentally friendly, consumable-free, and requires no chemical products or solvents because this method uses only a laser beam to vaporize the layer. Additionally, laser cleaning machines pose no risk to operators as these machines are designed to meet all safety standards.

Other major advantages of using laser cleaning technology include higher productivity, reduced mechanical damage to the surface, and remotability. Therefore, laser cleaning is currently the safest method available for rust removal. However, the difficulty in discriminating the separation threshold between the substrate and the contaminant layer is a major disadvantage of this technique.

Types of laser cleaning systems

Robotically controlled solid-state lasers used in tire mold cleaning demonstrated higher cleaning speeds than conventional abrasive cleaning methods. Similarly, a neodymium:yttrium aluminum garnet (Nd:YAG) laser cleaner was recently used to remove leaves from railway tracks. Nd: YAG lasers improve the flexibility of the cleaning process and are more reliable and free from operating errors than other lasers.

Large surface areas are laser cleaned using transversely excited ambient carbon dioxide (CO2) pulsed lasers with multi-kilowatt power outputs. The 10.6 µm laser output length of these lasers makes them ideal for cleaning metal substrates as metals are highly reflective of this laser wavelength, ensuring only organic containment is removed. However, it is difficult to achieve uniform energy distribution in high-power CO2 lasers.

Major industrial applications of laser cleaning technology

Laser cleaning is commonly used in steel fabrication for rust removal and surface profiling, anode assembly cleaning, adhesive bond preparation for metals, pretreatment for welding and brazing, partial de-coating, selective color removal, and dirt removal from metal mold surfaces.

New studies in laser cleaning technology

In a study published in the journal MATEC Web of Conferences, researchers experimentally investigated the effect of various key laser parameters, such as number of passes and scan speed, on removal and surface properties, such as surface profile, hardness, and surface depth. Roughness, after laser cleaning.

A moving pulsed laser beam was used to irradiate rusted mild steel specimens. Removal depth increased with increasing laser power and number of scans and decreased with increasing scan speed. After laser cleaning at high power and low speed of the laser, the surface was deformed and discolored.

The final surface roughness and surface profile after laser processing were dependent on the laser scan pattern. Thus, the surface roughness values ​​of the laser-cleaned parts were uncorrelated with the initial surface roughness values ​​before laser cleaning.

In addition, the surface hardness increased significantly after laser treatment. Microhardness values ​​vary with the scanning path of the laser beam, indicating changes in microstructure due to laser cleaning.

Single passes at high speeds result in a fairly clean surface, while multiple passes lead to random changes in surface topology at low speeds and specific changes in topology at high speeds.

In summary, unconventional laser cleaning technology has emerged as an eco-friendly and simple method and a viable alternative to conventional cleaning processes to increase the effectiveness and quality of cleaning metal surfaces.

More from AZoM: Improving the effectiveness of laser heat treatment with laser beam profiling

References and further reading

Hirmaz, MS (2019). Laser cleaning of metal surfaces: a review. International Journal of Scientific and Engineering Research, Volume 10, Issue 7. ISSN 2229-5518.

Marla, D., Singh, RK, Narayanan, V.2018). Laser cleaning for rust removal in mild steel: an experimental study on surface characteristics. MATEC Web Conference221, 01007.

Disclaimer: The views expressed here are those of the authors expressed in their personal capacity and do not necessarily represent the views of Limited T/A AZoNetwork, the owner and operator of this website. This disclaimer forms part of the terms and conditions of use of this website.

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