Pulsed lasers are generally used for surface cleaning. These differ in nominal power (usually from 50 to 1000W), but the pulse energy is also an important parameter. This must overcome the activation energy required to break the chemical bonds in the molecules of the material to be removed and to vaporise/sublimate it. The pulse energy of lower lasers is usually around 1 mJ. Such lasers are used for example for cleaning museum exhibits. The middle class of lasers has a pulse power of around 10 mJ. The higher category of lasers suitable for industrial applications has a pulse energy of up to 100 mJ. In addition to the deconator itself, i.e. the actual source of laser radiation, the optical apparatus, the optical fibre, the system of mirrors that oscillate the laser beam on the surface to be cleaned, etc. are very important. A high quality, lower power pulsed laser can be much more effective for cleaning than a cheap product with paper-thin power.

As with most electronic and optical devices, the difference between cheap products from the East and products from reputable manufacturers is both price and quality. East Asian manufacturers often use continuous beam sources for cleaning lasers. These do not have the possibility of adjusting basic parameters such as pulse energy, pulse length and frequency. Such lasers usually have relatively high power, but it is not possible to adjust the parameters to the cleaning process. It’s basically like removing dirt with a hacksaw – it works, but the resulting surface doesn’t match it.

Yes, it can and very effectively. Soot, flue gases and carbon absorb light very well at the most commonly used wavelength of cleaning lasers, 1064nm, and readily convert to gaseous form. The laser is also excellent for cleaning surfaces such as wood or painted surfaces. The laser can remove, for example, combustion fumes and soot from facades and walls, and remove the effects of fire. Laser removal of exhaust gases in engines and exhaust systems is equally effective.

Laser cleaning is non-contact. As a rule, there is no damage to the surface to be cleaned, but it is important to set the laser parameters correctly. For example, when cleaning high-value historical objects, such settings may take longer than the cleaning itself. Special care should be taken when cleaning wood and materials with low thermal conductivity. For cleaning metal objects, secondary heating and subsequent dilation must be taken into account. However, the risk of damage is minimal compared to other cleaning methods, e.g. for mould cleaning there is virtually no wear even with repeated cleaning. Similarly, polished, brushed or otherwise textured surfaces do not suffer surface distortion. Laser cleaning is also very well suited for cleaning steel surfaces in tokamaks and the nuclear power industry, for example, where the demands on surface preservation are extreme.

The cost of laser cleaning is usually based on hourly rates. The purchase cost of the cleaning lasers (in the order of many millions for powerful devices for industrial applications) is largely reflected in the price. On the other hand, laser cleaning is environment-friendly and very often does not require the dismantling of electrical connectors, bearings and other mechanical components, upholstery, etc. The final cost of cleaning can thus often be lower compared to other methods.

Most commonly, laser cleaning is used on surfaces made of various metals, steel, cast iron, stainless steel, aluminium, bronze, etc. Laser cleaning can also be used on plated surfaces. Here, it is necessary to set the appropriate parameters of the pulsed laser to avoid damage, but even here the cleaning is very effective. Inorganic building materials such as bricks, concrete, stone and glass (even through glass) or tiles can be cleaned very well. Wood is more complicated to clean. Here, its low thermal conductivity and thermal stability must be taken into account, but in many applications laser cleaning of wood is advantageous. For example, we have tested the removal of fire-resistant lacquers that are otherwise very difficult to sand. Surfaces where different materials are side by side, e.g. steel with duralumin (alternators, starters, pumps, generators) can be cleaned without problems. With the right settings, it is not necessary to dismantle and disassemble the objects to be cleaned, and a sensitively adjusted laser will not damage electrical connectors, bearings, etc.

Laser cleaning is based on so-called laser ablation, where the vast majority of the material being removed (usually more than 90%) goes into the gas phase, essentially evaporating. One of the primary advantages of laser cleaning is that there is no contamination of the surrounding area with abrasive dust, as with blasting, or liquid, as with pressure washing. Laser cleaning can be carried out indoors, on facades or structures in public (due to OSH, it is only necessary to avoid the risk of exposure to the laser beam), in the immediate vicinity of generators, hydraulic equipment, etc. Absolutely minimal secondary waste is generated and there is no spread of, for example, microplastics or particles from coatings containing heavy metals. Laser cleaning is very suitable for the removal of contaminants in the vicinity of watercourses and drinking water sources.

The pulsed laser can very effectively remove rust and other corrosion products, or most oxides and inorganic metal complexes such as aluminium, copper, tin, titanium, etc. The laser is very good at cleaning surfaces of grease, i.e. various oils, petroleum jelly, and quite often removes temporary anti-corrosive oils and waxes. The laser is very good at removing residues of petroleum products. The laser degreased surface is perfectly prepared, for example, for welding or for the application of new paint. Another application of cleaning lasers is the removal of paints and varnishes, where the effectiveness varies, it is usually necessary to test the laser for the application. Dark paints go better, colourless varnishes go reasonably well. Paints containing heavy metals such as sulfur can be effectively removed if safety rules are followed. There are also a number of special industrial applications, we have removed e.g. nickel and chromium carbide deposits from glass tubes, inorganic deposits in furnaces, comaxite chambers, vacuum chambers, graphite, polyurethane (PUR) foam, polyamide (PA) surfaces from sliding bushings etc. In combination with mechanical cleaning, we have successfully tested the removal of fire retardant coatings. The laser can be used to decontaminate surfaces from biologically active substances such as pharmaceuticals or to remove dust in cleanrooms.