Laser cleaning: how does the process work and when is it worthwhile?

A controlled laser beam strikes the layer to be removed. The energy applied ensures that rust, oxides, paint or other residues are removed from the surface. Mechanical contact with abrasives or blasting material is not necessary for this.

That is of particular interest in industrial manufacturing. Instead of processing an entire component, the laser can clean only a later welding or bonding surface, for example. At the same time, the technology can be automated and integrated into existing production processes.

Laser cleaning is not a process in which you simply have to choose the highest available wattage, however. Material, coating, layer thickness, laser type, energy density, processing speed and the desired result together determine which system makes sense for an application.

What is laser cleaning?

Laser cleaning is a process for the non-contact processing of surfaces with laser radiation. The laser is guided in a targeted manner across the area to be cleaned. Depending on the application, rust, oxide layers, scale, paint, coatings or industrial residues, for example, can be processed and removed.

Unlike grinding, no abrasive tool touches the component. Unlike sandblasting, no conventional blasting media such as sand, corundum or glass beads are fired at the surface either. This makes it one of the dry surface processes: neither water nor chemical cleaning media nor conventional blasting material is needed for the actual cleaning process.

That does not mean, however, that no residues arise at all. The removed material can be released as dust, particles, aerosol or other process emissions. Suitable extraction and filter technology is therefore an important part of a professional laser application.

How does laser cleaning work?

The laser beam transports a defined amount of energy to the surface. When this energy meets rust, paint or another coating, the layer absorbs part of the radiation. If sufficient energy is introduced, the material can be removed or released from the surface underneath.

What matters here is the difference between the layer to be removed and the base material. An example: there is rust on a steel plate. The corrosion layer has different optical and thermal properties from the steel underneath. A laser process set up accordingly can use these differences to process the rust layer preferentially.

The basic principle sounds simple. In practice, however, several parameters have to be matched to one another. These include, among others:

• Laser power, pulse energy, pulse duration and frequency
• Scan width, scan pattern and processing speed
• Focal position and working distance
• Material, type of coating and coating thickness

There is therefore no universal setting for all cleaning tasks. A laser that works very quickly on flash rust can require completely different parameters for a thick, multi-layer coating.

What does laser ablation mean?

One central term is laser ablation. Ablation means the targeted removal of material through the action of energy. In laser ablation, laser radiation performs this task. Once the material removal threshold of a layer is reached, material removal begins. The level of this threshold differs from material to material — and that is precisely what can be put to use.

The aim is to find a suitable process window: the energy should be high enough to remove the unwanted coating reliably. At the same time, the effect on the substrate underneath should remain as low as the particular application requires.

The statement that a laser can never in principle affect a base material is therefore too sweeping. Laser energy can change a surface too if unsuitable parameters are chosen. Professional laser cleaning therefore does not mean maximum power, but the right power.

Pulsed laser or CW laser – what is the difference?

Two basic operating modes are used above all in processing: pulsed lasers and CW lasers.

Pulsed laser

A pulsed laser delivers its energy in short individual pulses. High peak powers can therefore arise within very short periods, even though the average laser power is comparatively moderate. This controlled energy input makes pulsed lasers particularly interesting for applications in which precision and thermal loading that is as limited as possible are important.

• precise rust removal and paint removal on smaller areas
• Tool and mould cleaning
• Weld seam processing and more sensitive metal surfaces
• Restoration work and local surface preparation

CW laser

CW stands for continuous wave, that is, continuous-wave operation. The laser delivers its power continuously. This makes powerful CW systems suitable in particular for robust applications where a high area coverage rate is required. Typical fields of application can be larger metal surfaces, heavier rust layers or extensive paint removal tasks.

The question is therefore not which laser has more watts. It is: which type of laser achieves the required result on my specific surface at the necessary speed? A pulsed laser with a few hundred watts and a CW laser with several kilowatts can have completely different task profiles.

Which materials can be cleaned with a laser?

The process is used particularly often on metal surfaces.

Steel

Steel is one of the classic materials. Typical applications are rust removal, paint removal, scale removal and surface preparation.

Stainless steel

On stainless steel, oxide layers, heat tint or production residues, for example, can be processed.

Aluminium

Aluminium can also be cleaned with a laser. Because of its material properties, however, the parameters should be matched specifically to the alloy and the surface.

Copper

Copper can be processed as well. Because of its high thermal conductivity and its optical properties, a material test is particularly advisable.

Besides metals, there are applications on other materials, including stone, concrete, clinker brick, wood and certain historical surfaces. With such materials it applies even more strongly: a test area is advisable before larger areas are processed.

What can be removed with a laser cleaning machine?

The possible applications go well beyond rust removal alone.

• Rust and other corrosion products — the best-known application
• Paint: suitable paint and coating systems, completely or step by step
• Oxide layers on steel or stainless steel, before or after welding processes
• Scale: thermally formed oxide layers, depending on the material and the thickness
• Heat tint: discolouration that arises during welding work
• Production residues on tools and moulds
• Oil and grease residues from the process

One important advantage lies in the option of exposing only certain areas of a surface. A later welding area, bonding area, contact area or coating area, for example, can be cleaned selectively. The entire component does not necessarily have to be processed for this.

What advantages does laser cleaning offer?

The advantages depend on the particular application. Some characteristics, however, distinguish the process fundamentally from conventional methods:

• Non-contact — no direct mechanical tool contact
• Without conventional blasting media — no sand, corundum or glass beads
• Precise — the laser can be guided in a targeted manner over defined areas
• Automatable — can be combined with robots, axis systems and production lines
• Repeatable — identical component areas with defined settings
• Dry — no liquid cleaning medium for the removal
• Selective — depending on the material combination, individual layers can be processed in a targeted manner

This selectivity is of particular interest in industrial production processes. If only a bonding area 20 millimetres wide is needed, for example, the entire component does not necessarily have to be cleaned.

Where are the limits of the process?

Laser cleaning is not automatically the most cost-effective process for every task. On very large, robust surfaces, conventional blasting processes can achieve a high area coverage rate. Very thick coatings can also take up a great deal of time. Further points that have to be taken into account:

• Investment costs: professional systems are capital goods — whether the purchase is worthwhile depends largely on the subsequent utilisation
• Safety: powerful open applications place high demands on the workplace, shielding, instruction and laser protection
• Process emissions: the removed coating has to be captured or extracted
• Material dependency: not every material reacts in the same way — new applications should be tested
• Area coverage rate: technically clean processing is not automatically cost-effective if it takes too much time

The question should therefore never be only whether something can be removed. How quickly and with what result this is achieved is at least as important.

Laser cleaning in industry

The technology becomes particularly interesting where cleaning is part of a production process. A component can be prepared in a targeted manner before welding, bonding, coating, painting or assembly. A robot can, for example, follow a defined contour and clean exactly the area on which an adhesive joint is subsequently made.

The Fraunhofer Institutes for Laser Technology (ILT) and for Material and Beam Technology (IWS) have been working on such laser-based cleaning and pre-treatment processes for years. Besides removing rust and coatings, lasers are also used for surface activation and for preparing joining processes. With high unit numbers in particular, this can become a reproducible production step. More on this on our page about industrial use in day-to-day operation.

How fast is laser cleaning?

A blanket figure such as “X square metres per hour” says only so much without a specific application. The speed depends, among other things, on the type of contamination, the layer thickness, the material, the type and power of the laser, the scan width, the number of passes required and the desired final condition.

Light flash rust can be considerably quicker to process than a multi-layer paint system. The processing objective also plays a role: should a surface merely look clean, or is a technically defined surface needed for a subsequent bonding or welding process? These requirements can lead to markedly different process times. A test on the original material is therefore the most reliable basis for a realistic calculation.

When is a laser cleaning machine worthwhile?

A laser cleaning machine of your own becomes interesting above all when such work arises regularly. Companies should not look exclusively at the purchase costs, but at the total current process costs. These can include:

• Working time and external cleaning service providers
• Blasting media, abrasives and chemical cleaning media
• Disposal and transport of components
• Machine downtime and rework

These costs are then set against the investment and the running costs. New business opportunities can be part of the calculation as well: with a mobile machine, a service provider can offer additional rust removal, paint removal or restoration services. In a manufacturing company, by contrast, optimising its own processes is often the main focus.

Buy, hire or commission the cleaning?

Not every business has to buy a machine of its own straight away. There are essentially three options.

Buying a machine

Buying is particularly interesting when the machine is needed regularly and there is corresponding utilisation. Our overview of the available machines sets out the power classes.

Hiring a machine

For individual projects or trial phases, hire can make more sense. It makes it possible to use the technology under real conditions in your own operation without making the full investment straight away.

Cleaning as a service

If components only rarely need cleaning, commissioned processing can be more cost-effective. The decision should not be made on gut feeling: frequency of use, processing volume and current process costs provide a much better basis.

Why a material test makes sense

When choosing a machine, a material test is one of the most important steps. A data sheet states what power a machine has. The material test, by contrast, shows:

• whether the coating can be removed
• what the base material looks like afterwards
• which parameters are suitable and how many passes are needed
• what processing speed is realistic
• which power class makes sense

Where several systems are possible, a comparison on the original component can be very helpful. Beamlux therefore offers material tests and live demonstrations. The aim should not be to sell the most powerful machine as a matter of course, but to determine the system that makes technical and commercial sense for the specific application.

Safety in laser cleaning

Professional hand-held machines can be class 4 lasers. These systems have to be taken seriously accordingly. Hazards can arise from direct and reflected laser radiation, eye and skin exposure, process emissions and fire risks, among other things. Commercial applications therefore require an application-specific risk assessment and suitable technical, organisational and personal protective measures.

Suitable process extraction is important too. When rust or coatings are removed, the material does not disappear: particles, dusts, aerosols and — depending on the coating — further substances can arise.

With the FBHM-139 guidance document, the German Social Accident Insurance (Deutsche Gesetzliche Unfallversicherung) has published a point of reference specifically for cleaning and coating removal with hand-held class 4 laser devices. Among other things, it covers laser radiation, the hazardous substances produced, extraction and organisational protective measures. This makes one thing clear: a laser cleaning machine is a powerful industrial tool — and should be operated with a corresponding degree of professionalism. You will find a summary of the most important points on our page on safety with laser class 4.

Conclusion: not a replacement for everything, but a strong alternative

The process combines several characteristics that are of interest for modern industrial surface processes: it works without contact, needs no conventional blasting media and can be used very locally. At the same time, the technology can be automated and integrated into existing production processes.

It is particularly suitable wherever the aim is not simply to remove as much material as quickly as possible, but where a defined surface condition is needed. Rust removal, paint removal, oxide removal, mould cleaning and the preparation of welding or bonding areas are among the most important applications.

Whether a machine pays off for a particular business, however, cannot be judged from the wattage alone. Five questions are decisive: which material is to be processed? What is to be removed? How large is the area? How often does the processing take place? What result is required?

That explains the process in its basic outlines — but applying it to your own component remains a question of practice. This is precisely why a material test is often the most sensible way to start. Before deciding between pulsed laser, CW laser, purchase, hire or a service, you can check on the real workpiece which approach actually works and what processing speed can be achieved.

Frequently asked questions

Related terms in the glossary

The following technical terms are defined in one place in the Beamlux glossary — where you will find a total of 160 entries from ablation to scale.

Sources

• Fraunhofer Institute for Laser Technology ILT — laser-based cleaning processes, rust and coating removal, surface preparation.
• Fraunhofer Institute for Material and Beam Technology IWS — laser cleaning, surface pre-treatment and industrial process integration.
• German Social Accident Insurance (DGUV) — FBHM-139 “Strahlarbeiten – Reinigen und Entschichten mit Laserstrahlung”, guidance document for hand-held class 4 laser devices, edition 06/2024.
• Federal Institute for Occupational Safety and Health (BAuA) — TROS Laserstrahlung, technical rules on the ordinance on occupational health and safety relating to artificial optical radiation.

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