METHOD FOR SURFACE TREATMENT AND USE OF AN ADDITIVE

Description

[0001] The present disclosure relates to a method for surface treatment of a workpiece using abrasives. The disclosure further addresses the phenomenon of high flammability or even spontaneous combustion of waste products during surface treatment. In addition, the disclosure relates to a surface treatment agent for surface treatment of a workpiece. The disclosure addresses measures for reducing the tendency of waste products to spontaneous combustion.

[0002] US 2008 / 066512 A1 discloses a shot peening device comprising a housing in which an interior space is formed, a movable carriage for movably supporting an object to be treated in the interior space, at least one ejection means for ejecting blasting media particles onto the object carried by the carriage, a circulation system with a collection plane on which the ejected and fallen blasting media particles are collected by the circulation system in order to return the collected blasting media particles to the ejection means, keep them circulating, and use them for ejection, and at least one removal means for removing impurities from the blasting media particles. For this purpose, a dust collector is provided for collecting dust, with an ignition suppressant being added to the dust.

[0003] From EP 1 726 364 A2 a comminution process for chips or chip mixtures as well as compacts from chips of metals or metal alloys is known, wherein the material to be comminuted is comminuted in the presence of a non-flammable liquid, preferably water or an aqueous solution, in an impact crusher, preferably a hammer mill.

[0004] From US 2011 / 219704 A1 a method for recycling a cerium oxide abrasive used in polishing a glass material is known, the method comprising adding a strong alkali solution to a slurry waste of the cerium oxide abrasive, adding sodium fluoride to the slurry waste, and separating cerium oxide particles contained in the slurry waste from other particles.

[0005] US 2 031 362 A deals with the manufacture and application of sandpaper, with emphasis being placed on water resistance and reduced tendency to ignition of the sandpaper itself.

[0006] The present disclosure generally relates to the field of surface treatment, in particular the field of mechanical surface treatment. Where the term surface treatment is used in this document, it primarily refers to polishing processes, brushing processes, grinding processes, compressed air blasting processes, and similar processes that remove material or level surfaces. Furthermore, the term surface treatment also refers to machining processes in which workpieces are machined, with the removed material being produced in the form of chips. Machining processes or cutting processes include, for example, turning, drilling, milling, and grinding. Polishing, brushing, grinding, compressed air blasting with blasting material, and machining processes in general can generally be considered subgroups of smoothing machining processes.Brushing applications, polishing applications, blasting applications, grinding applications and machining processes can partially overlap technologically.

[0007] Polishing, brushing, air-jetting, grinding, and machining processes generally serve to reduce the surface roughness of components and, preferably, to create a shine on the surface of the component. Applications are also conceivable where burr removal or similar processes are the primary focus. The transition from polishing to grinding is often fluid. Polishing applications are frequently encountered in the field of mechanical precision machining, especially in the field of mechanical surface finishing.

[0008] The present disclosure further relates in particular to the fields of industrial grinding, turning, drilling, milling, brushing, compressed air blasting, and polishing, and preferably highly automated grinding, turning, drilling, milling, brushing, compressed air blasting, and polishing. Grinding devices, brushing devices, compressed air blasting devices, machining devices, or polishing devices are known, which comprise, for example, machining cells in which, on the one hand, the surface processing device itself is provided, but, on the other hand, elements for automatically feeding workpieces to be machined are also provided. For example, handling devices such as robots, rotary transfer machines, or flatbed polishing machines can be provided, which are designed to grip workpieces to be machined and bring them into contact with the machining tool.

[0009] In this case, it is fundamentally irrelevant whether the workpiece and / or the tool are actively moved relative to the other element. In addition to workpiece-guided machining, tool-guided machining is also known. Here, the workpiece is secured in a corresponding holder and then machined by the tool mounted on a movable head. This type of machining is used, for example, for machining large workpieces. Furthermore, the handling devices can be designed to effect a relative movement between the workpiece and the machining tool in order to machine the desired areas of the workpiece. In other words, a handling robot can be provided that imitates a "manual" pivoting or displacement of the workpiece relative to the (rotating) machining tool.

[0010] Surface treatment agents used are those with an abrasive effect, such as abrasive grains. Examples of abrasives include polishing agents, brushing agents, blasting agents, or grinding media. These are typically offered in defined dosage forms or states. These can be solids, solid pastes, or emulsions. Polishing agents or similar materials can also be in the form of ointments, creams, and / or polishes.

[0011] For the purposes of this disclosure, abrasives also include parts of a machining tool. These parts include, for example, parts that can be replaced after machining, such as indexable inserts. However, the abrasives can also be a cutting material incorporated into the machining tool, such as tool steel, cemented carbide, cutting ceramics, boron nitride, or diamond.

[0012] The present disclosure relates to polishing according to exemplary embodiments. Polishing is typically based on various principles. On the one hand, a certain amount of material is removed during polishing. Furthermore, roughness peaks in a surface structure of the workpiece are typically deformed and, in particular, leveled during polishing. Furthermore, cavities or unevenness can be at least partially filled during polishing.

[0013] Polishing devices include, for example, a polishing wheel, a polishing plate, or a polishing belt. The polishing wheel can provide a carrier material made of natural materials (natural fibers, cotton, sisal, paper, etc.) or artificial materials (synthetic fibers). Sponge-like materials can also be used for polishing wheels. Polishing is typically performed by applying a suitable polishing agent to the polishing wheel. Due to a relative movement between the polishing wheel and the workpiece to be machined, the polishing agent can come into contact with the workpiece to process it, particularly by smoothing it.

[0014] Polishing discs, brushes, or similar polishing tools can have working areas that include materials such as cotton, sisal, polymers, paper, felt, leather, or similar components. Grinding discs are generally made of harder materials. They often contain metals or ceramics. Generally, the disc (for polishing, brushing, or grinding) can be referred to as a polishing agent carrier. The abrasive grain can be based on alumina, corundum, aluminum oxide, aluminum hydroxides, aluminum silicates, magnesium aluminum silicates, calcium carbonates, chromium trioxide, cerium oxide, quartz, iron oxide, silica, or similarly hard materials.

[0015] The present disclosure relates to the surface treatment of workpieces whose surface to be treated preferably consists of metals or metal alloys, in particular of light metals, light metal alloys, or non-ferrous metals or non-ferrous metal alloys. For example, the surfaces consist of magnesium, aluminum, titanium, iron, copper, zinc, and the like, or of corresponding alloys containing these, such as brass, bronze, and the like. During the treatment of workpieces, material removal occurs. For example, the uppermost layer of the surface of the workpiece is removed. The treatment can at least partially comprise leveling. Furthermore, surface treatment also relates to the machining of workpieces, wherein not only the surface is removed, but the workpiece is also milled, turned, or drilled, for example.

[0016] Furthermore, according to exemplary embodiments, the present disclosure relates to sandblasting. Sandblasting is generally understood to be the process in which the surface of a workpiece is processed by means of compressed air blasting with solid blasting material through the action of the blasting media. For example, sand, glass beads, glass granulate, corundum, high-grade corundum, chilled cast iron, cast steel, stainless steel, ceramic, plastic, duroplast, natural core, brass grit, garnet sand, Sibasiv, or other suitable blasting media can be used as blasting media. During surface processing by sandblasting, blasting debris remains, which, together with the removed material, is generated as waste. Depending on the blasting media used, the removed material often occurs as dust, which can lead to dust explosions.To at least partially limit this dust explosion, the blasting material is often collected along with the resulting waste in a wet scrubber. Despite this measure, unwanted fires still frequently occur within the wet scrubber.

[0017] It has been observed that accumulations of waste such as grinding waste, brush waste, blasting media waste, machining waste, or polishing waste, especially waste generated during the processing of metals, especially light metals, are highly flammable. In extreme cases, this can even lead to spontaneous combustion of the waste. Depending on the waste products generated during surface treatment, the waste products can ignite at different times during the surface treatment process. For example, polishing waste, which consists of light metal dust mixed with polishing agent and water, is easily prone to spontaneous combustion. In this case, the waste heats up spontaneously, for example, due to oxidation or other reactions between the individual components of the waste (metal dust, metal shavings, greases, oils, waxes, etc.).), which lead to heating and ultimately spontaneous combustion of the waste, especially if there is insufficient heat dissipation. Such waste is usually collected over a period of time and disposed of. Such waste is often stored on the company premises away from other facilities to minimize collateral damage in the event of a fire.

[0018] If the waste products are metal dusts, such as those generated during blasting, these dusts must be removed from the ambient air. In such processes, limit values ​​for the dust content in the air must be observed. A wet scrubber, for example, can be used to remove dust from the air; the resulting dust is bound in water. In addition to removing dust from the air, wet scrubbers offer the additional advantage of containing dust explosions from metal dusts. However, the metals can react with water to form highly flammable hydrogen, which in turn is a combustible gas.

[0019] It is generally believed that the ignition of such grinding, brushing, blasting, machining, and polishing waste cannot be completely prevented. This is also reflected in the fact that such fires have been documented even in highly developed countries with stringent safety requirements.

[0020] Against this background, the invention is based on the object of providing a method for surface treatment of a workpiece in which at least some of the disadvantages described above can be reduced, preferably avoided. In particular, the method is intended to contribute as far as possible to reducing the tendency of processing waste, in particular grinding waste, brushing waste, blasting waste, machining waste, or polishing waste, to self-ignition. Furthermore, the invention is based on the object of specifying a surface treatment agent, in particular a grinding, brushing, or polishing agent, that reduces the tendency of the waste to self-ignition as far as possible. Furthermore, the object of specifying the most advantageous uses of suitable additives is intended.

[0021] Regarding the method, the object of the invention is achieved by a method for surface treatment of workpieces by means of abrasively effective means, wherein the method comprises the following steps: Provision of a machining tool; provision of an abrasive agent; feeding a workpiece with a surface to be machined; surface machining of the workpiece, comprising material removal, whereby waste products are generated; and processing of the waste products by wetting the waste products; wherein at least one of said steps comprises the following: addition of an additive for reducing a tendency of the waste products to self-ignite, wherein the additive contains a salt of a carbonate and / or a halogen anion.

[0022] The object of the invention is thus completely solved.

[0023] According to a further aspect, the present disclosure further relates to a method for surface treatment of workpieces, the method comprising the following steps: Providing a machining tool; feeding a workpiece with a surface to be machined; surface machining of the workpiece, comprising material removal, whereby waste products are generated; and processing the waste products by wetting the waste products; wherein at least one of said steps comprises the following: adding an additive to reduce a tendency of the waste products to self-ignite, wherein the additive contains a salt of a carbonate and / or a halogen anion.

[0024] According to the invention, the tendency of the resulting waste products to self-ignite can be reduced by adding the additive by reducing the reactivity of the potentially hazardous waste components. For this purpose, the additive, which contains a salt of carbonates and / or halogen anions, is added in at least one of the process steps. By wetting the waste products, the additive can dissolve in the solvent used for wetting, for example, water, and react with the waste components.

[0025] In this case, it is initially irrelevant how the additive is added, as long as the additive is present in the waste products in the desired way or can react with a component of the waste.

[0026] Where this disclosure refers to the feeding of a workpiece with a surface to be machined, this covers any type of relative feeding movement. In other words, this can involve a movement of the tool and / or a movement of the workpiece.

[0027] It was recognized that the fires or spontaneous combustions are due to specific properties of the waste products and their mechanisms of action. This also involves a departure from previously generally accepted theories regarding the causes of the frequency of fires involving waste products from surface treatment, particularly polishing, brushing, grinding, machining, pressure blasting, and similar material-removing or smoothing processes.

[0028] Waste products in the form of metal chips and metal dust can arise from the workpiece. The resulting metal dust can contain particles that are sometimes smaller than 500 µm. Metal chips, which are particularly produced during machining processes such as grinding, turning, drilling or milling, are composed of correspondingly larger particles. The dust and chips are extremely reactive and tend to combine with the oxygen in the ambient air, generating a great deal of heat. This can also lead to so-called dust explosions. To limit dust explosions as much as possible, the dust waste can be collected with a solvent, such as water. The metal dust reacts with the solvent. However, this process forms highly flammable hydrogen, which in turn can react with the oxygen in the air in a so-called oxyhydrogen reaction.However, the highly flammable hydrogen can also be ignited by surrounding heat sources. Therefore, all waste products can pose an increased fire hazard. This depends on the type of metal, the concentration, and the particle size.

[0029] In addition to the dust particles from the workpiece, other waste products are generated during surface processing, which in turn can pose an increased fire hazard. These can include abrasion from the processing tool and residues of the abrasive. Typically, it can be assumed that 20% to 50% of the abrasive is simply thrown away during processing, so this amount is generated directly as a waste product. As a result, the abrasive represents a significant proportion of the waste.

[0030] For the purposes of this disclosure, "abrasive agents" are understood to mean, for example, solid particles, abrasives, cutting materials, or blasting media. Abrasive agents can be contained, for example, in polishing agents, brushing agents, or grinding media. Furthermore, abrasive agents can also be part of the machining tool itself, e.g., cutting materials such as tool steel, hard metal, cutting ceramics, boron nitride, or diamond.

[0031] For the purposes of this disclosure, "waste products" are understood to mean all parts generated during the surface treatment process or superfluous parts that are not connected to the workpiece being treated. The various waste products are collected, for example, and processed by wetting. "Waste" in this context refers to the sum of all "waste products" that accrue during surface treatment, for example, as sludge or in the form of briquettes. The sum of all accrued waste products forms a mixture of potentially flammable materials, which can further increase the fire hazard. Waste products also include products that arise during surface treatment through oxidation; for example, highly flammable hydrogen, which can form during the reaction of metal dust and water.

[0032] Typically, waste products are processed by wetting, for example, for disposal and / or safety reasons. This prevents the release of dust, for example, by precipitating the dust with liquids to prevent any reactions of the metallic component as far as possible. Possible processing methods include the following: wet processes; dry processes with wet separation of the dust by immediately wetting the released dust; and dry processes with wet separation of the dust by wetting the dust in a wet scrubber. These processes are regulated, for example, by occupational health and safety regulations and represent a first processing step for the resulting waste products.

[0033] In wet processes, the workpiece and / or the machining tool are wetted with water or other suitable cooling lubricants so that the resulting abrasion is produced as a slurry or mixture. The metal dust and metal chips removed from the workpiece can react with the water or other suitable cooling lubricants.

[0034] In dry processes with wet separation of waste products by immediately wetting the released waste, the waste is wetted immediately behind the point of origin with water, possibly with expansion additives or other suitable liquids, so that it is bound as completely as possible and accumulates as sludge or a mixture. The processing machine and liquid addition are coupled in such a way that dry operation is not possible.

[0035] In dry processes with wet separation of waste products in the wet separator, the waste products generated are extracted as completely as possible at the point of origin and fed into a suitable wet separator.

[0036] The aforementioned treatment methods primarily aim to dedust the air and, furthermore, to prevent dust explosions from the dry waste products consisting of the smallest surface particles of the workpiece. However, it has been observed that the resulting "wet waste" or sludge generated during any of the above-described treatments continues to pose a fire hazard. According to one aspect of the present disclosure, this tendency toward spontaneous combustion can be minimized by adding an additive. This potential fire hazard cannot currently be effectively counteracted in any other way.

[0037] The potential danger posed by this waste stems from the presence of small and extremely small metallic particles in the remaining matrix (e.g., from liquids, particularly water, fats and oils; waste products, etc.) which, due to their large surface areas, react with atmospheric oxygen, water, and moisture, possibly generating heat. Since this reaction is exothermic (i.e., releasing energy / heat) and the reaction rate generally increases with temperature, and waste storage facilities are often designed to cause heat buildup (e.g., in larger containers), such reactions are expected to occur at an accelerated rate.Under such conditions, hydrogen is regularly produced (in the extremely reactive "status nascendi"), which can even lead to spontaneous combustion, possibly together with any parallel exothermic oxidative reactions of the metals.

[0038] The likelihood of spontaneous combustion of (initially wet) waste, especially waste that is stored, is further increased by the evaporation of water. For example, waste is collected in open containers, which causes water to evaporate. As a result, the waste becomes increasingly dry over time, and the concentration of combustible substances within this waste increases. Wet waste has the advantage of inherent cooling, whereby the temperature of the waste can be kept below 100°C, for example. Furthermore, the water can react with the uppermost layer of metals to form a protective layer. Evaporation of water is therefore fundamentally disadvantageous, as the tendency towards spontaneous combustion depends on the degree of dryness of the waste. Evaporation depends on the ambient temperature, so that this type of waste can ignite quickly, especially in warm weather.This can happen, for example, in warehouses or during transport in open containers; even trucks can catch fire, which can cause major damage.

[0039] The probability of spontaneous combustion typically increases with the surface area of ​​the metallic particles, the degree of dryness of the waste, and the associated decrease in residual moisture content. While compact, solid pieces of metal rarely react dangerously except when exposed to acids, alkalis, or hot water, or when heated above their melting point (involvement in a fire), small-scale metal particles such as powder, metal grains, and fine chips exhibit different properties due to their significantly larger surface area.

[0040] The tendency of the resulting waste products to self-ignite increases the complexity of the surface treatment process itself. Furthermore, storage, transport, and disposal of the waste products are made more difficult.

[0041] In general, and within the scope of this disclosure, self-ignition is understood to mean the process in which a system heats itself (up to an ignition temperature) through its own energy input to such an extent that any combustible substances present are ignited. This can include the ignition of a combustible substance without the influence of an ignition source, i.e., without external ignition by sparks or flames. The ignition temperature is the temperature at which substances exhibit self-ignition on hot bodies (ignition temperature).

[0042] The ignition temperature and the ability to self-ignite depend on the residual water content, pressure, oxygen concentration, and catalytic influences. The ignition temperature of substances or mixtures of substances can be reached when exothermic reactions (with heat release) occur within them, the heat of which cannot be dissipated to the outside. Self-ignition processes are divided into the stages of self-heating and self-ignition. The prerequisite for the temperature increase is a chemically reacting substance or a biologically induced process that provides the necessary energy. The required amount of heat is generated by a spontaneous chemical reaction (e.g., auto-oxidation) or physical processes (friction, impact, electrostatic charging) in or on the surface of the combustible materials themselves.Most self-heating and ignition processes require a warm-up period, combined with heat buildup, and the right amount of atmospheric oxygen. Strong oxygen adsorption on fine-particle surfaces (dust) can also cause spontaneous combustion.

[0043] According to an exemplary embodiment, the salt contains a carbonate and / or a halogen anion. The halogen anion is preferably a fluoride. According to exemplary embodiments, the additive consists of the salt. According to alternative embodiments, the salt forms a component of the additive.

[0044] According to an exemplary embodiment, the surface of the workpiece to be machined can preferably consist of metals or metal alloys, in particular of light metals and / or light metal alloys, or in particular of non-ferrous metals and / or non-ferrous metal alloys. According to this disclosure, the surface of the workpiece can be in the form of a coating, so that the base body of the workpiece can consist of a different material.

[0045] In this disclosure, the terms "light metal", "light metal alloy", "non-ferrous metal", "non-ferrous metal alloy", "metal alloy" and "metal" are used.

[0046] Light metals are generally referred to as metals and alloys with a density of less than 5 g / cm². Aluminum, magnesium, titanium, and, to a lesser extent, beryllium and lithium, as well as other elements, can be used as alloying elements in low concentrations. In recent years, the use of light metals has gained increasing importance. This is due to their material properties, such as their low density, the associated low moment of inertia, and the low weight of the products. The ease of forming workpieces (e.g., by casting or injection molding) and their relative ease of machining are also advantageous.

[0047] Examples of non-ferrous metals include cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), tin (Sn), and zinc (Zn). These metals are characterized by their color, which occurs both in their pure form and in corresponding alloys. Non-ferrous metals have a higher density (over 5 g / cm²) than light metals and are therefore considered heavy metals. Examples of non-ferrous metal alloys include brass (copper and zinc) or bronze (copper and tin). Other preferred alloys are those of non-ferrous metals and other non-ferrous metals, or aluminum, titanium, magnesium, etc.

[0048] Experiments have shown that the oxidation of metal particles from the material removal from the workpiece is a primary cause of the spontaneous combustion of the waste product or waste itself. This applies to all of the metals mentioned above and can, in principle, affect other metals. The metal particles can form so-called hotspots. This leads to self-heating of the waste and ultimately to spontaneous combustion. This finding was particularly surprising because it was previously assumed that the fine-grained, particle-containing material removal could be rendered non-reactive simply by wet processing.

[0049] If the waste contains fats or oils, such as those found in polishing agents, it has been assumed that the unsaturated compounds of the oils / fats in the abrasive agent, when distributed over a large surface, generate sufficient heat through direct oxidation with atmospheric oxygen to trigger a smoldering fire and ultimately an open flame under appropriate conditions. In other words, it has previously been assumed that the tendency to spontaneous combustion arises from the hydrogenation of the double bonds in the fats, and that the resulting heat ignites the metal particles. However, this is not the primary cause of spontaneous combustion.

[0050] In general, carbonates are understood to mean salts and esters of carbonic acid (H 2 CO 3 ). For the purposes of this disclosure, carbonates are understood to mean, in particular, the salt of carbonic acid. Two series of salts are derived from the diprotic (dibasic) acid: the hydrogen carbonates, also called primary carbonates, with the general formula M +< HCO 3 , and the secondary carbonates, with the general formula M+ 2< CO 3 . The secondary carbonates are based on the doubly negatively charged carbonate ion CO 3 2-< . These carbonates are a preferred component of the additive for the purposes of this disclosure.

[0051] Halide anions or halides are generally, and also within the scope of this disclosure, the singly negatively charged ions of the elements of the seventh main group (more precisely, the 17th group) of the periodic table, i.e., the halogens (F -< , Cl -< , Br -< , I -< , At -< ). The terms halides and halogen anions are used synonymously in this disclosure. Halides form compounds that differ based on their chemical bonding.

[0052] The first group consists of ionic compounds (salts), which, due to the large electronegativity difference between the elements involved, consist of anions and cations and are held together by electrostatic interactions. Halides can also form covalent bonds; in these compounds, the electronegativity difference is not as large as in the previously mentioned ionic compounds. The bonds nevertheless exhibit charge polarities. Another group of halides consists of compounds in which the halide ions are bound as a complex. In other words, the halide anions are present as ligands. For the purposes of this disclosure, the halide anions can be present in any form in the additive or ultimately in the waste.

[0053] By adding an additive containing a salt of a carbonate and / or a halogen anion, the metals are bound in an unreactive form, for example as a complex or salt. The resulting compounds can be, for example, magnesium carbonate (MgCO3), aluminum carbonate (Al2(CO3)3), zinc carbonate (ZnCO3), magnesium fluoride (MgF2), aluminum fluoride (AlF3), zinc fluoride (ZnF2), or titanium fluoride (TiF4). In other words, a chemical reaction occurs between the metals and the carbonates and / or halides, so that the combustible metals are no longer available as reaction partners.

[0054] Where the term "unreactive form" is used in this disclosure, this means, for example, that a corresponding substance is no longer classified as flammable or capable of self-ignition. According to this disclosure, unreactive substances include, in particular, those that are not classified in the GHS labeling class GHS02. This class covers highly flammable, highly flammable, and flammable substances.

[0055] The additive can generally be added in at least one sub-step of the surface treatment process, provided that the additive is ultimately present in the waste products or waste. For example, the additive can be added in several of the steps, especially if there is a risk of particularly flammable dusts being generated. For example, the processing tool can contain the additive in addition to the abrasive agent. Alternatively or additionally, the additive can be added in the sub-step of processing the waste products.

[0056] According to a further embodiment of the method, the surface of the workpiece to be machined consists of magnesium, magnesium alloys, aluminum, aluminum alloys, titanium, titanium alloys, zinc or zinc alloys.

[0057] Metallic magnesium, magnesium alloys, aluminum, and aluminum alloys have now established a firm position in the production of consumer goods, whether as a material in mechanical engineering, automobiles, and aircraft construction or in a wide variety of everyday objects, particularly in the building hardware industry. These metals are of particular interest in lightweight construction technology. They form lightweight materials, for example, for automotive applications. The use of these metals can significantly improve the economic efficiency of a vehicle. Zinc and its alloys also have diverse applications. Preferred alloys include brass alloys. Brass has the advantage of being easy to process and form. Alloys of zinc with aluminum and magnesium are used to produce vehicle parts, among other things.

[0058] The majority of magnesium produced is used for aluminum alloys. However, components made from alloys with magnesium as their main component are also produced. A distinction is made between aluminum alloys with up to 11% magnesium and the actual, extremely lightweight alloys with magnesium as the main component.

[0059] However, the disadvantage is that these metals (Mg, Al, Ti, and Zn) can easily ignite, especially in the form of tiny particles such as metal dust or metal shavings. This can happen even after prior treatment with a solvent, such as water.

[0060] Chemically, aluminum, magnesium, titanium, zinc, and other metals have an enormous affinity for oxygen. This is evident, for example, in a thin film of oxides that forms almost instantly when tiny metal particles are exposed to the atmosphere. The oxide film is inert and protects the underlying metal from further attack. When a metal powder particle is heated to the ignition point, the particle mass is so small that the entire particle can oxidize almost instantly. Thus, a large portion of these particles will "burn up."

[0061] According to an exemplary embodiment of the process, the salt is selected from the group consisting of sodium carbonate, potassium carbonate, and sodium fluoride. Combinations of these are also conceivable. These salts offer the advantage of being particularly cost-effective and readily available commercially. Furthermore, the salts are easy to handle due to their solid state (at room temperature). Sodium carbonate and potassium carbonate are also non-toxic salts, so no further hazards are expected from these salts.

[0062] The waste products are processed by wetting. As already explained above, the resulting waste products are preferably captured using wet chemicals. This initially reduces the risk of fire or explosion to a lower level. By adding the additive in a sub-step of the process, the tendency to self-ignition and the associated fire hazard are further reduced, preferably to a level that is tolerable under the specific circumstances.

[0063] Wetting the waste products can be carried out with any suitable liquid within the meaning of this disclosure; for example, pure solvents such as water, but also suspensions such as milk of lime, can be used as the washing liquid. A person skilled in the art will know how much liquid to use. Parameters to consider here include fire prevention, the cost of disposing of the resulting waste, the type of liquid, etc.

[0064] According to a further embodiment of the process, the waste products are processed in a wet scrubber, resulting in the generation of wet waste. This embodiment differs from the aforementioned embodiment only in the use of a wet scrubber. The liquids used can be used analogously.

[0065] In general, and within the scope of this disclosure, a wet scrubber or so-called absorber is understood to be a process-engineering apparatus in which a gas stream is brought into contact with a liquid stream. The mode of operation of wet scrubbers is based on the transfer of particles from a flowing, particle-laden gas into a liquid. To achieve this, appropriate phase boundaries must be formed between the gas and liquid, and relative movement must be generated between these two phases. One method of achieving phase boundaries with the most intensive possible mixing of gas and liquid is the dispersion of one phase into the other. This means, for example, generating swarms of bubbles in a liquid or collective droplets in a gas, or systems in which the liquid is present as a more or less dispersed jet.Another fundamental possibility for bringing gas and liquid into contact is the flow around liquid-wetted bodies. The large number of variants found in wet scrubber systems is based on the variety of ways to form phase boundaries and generate relative motion between gas and liquid.

[0066] The components of the gas stream that pass through can be solid, liquid or gaseous substances, in particular the waste products that arise during surface treatment.

[0067] According to a further embodiment of the process, the additive is added within the wet scrubber and / or into the wet waste. This embodiment offers the advantage that the additive is completely present in the wet waste, thus reducing its tendency to self-ignite. The carbonates and / or halide anions can react directly with the flammable metals in the liquid, particularly aqueous, waste to form non-reactive compounds.

[0068] The additive can be added in solid form or in diluted form, for example, dissolved in a solvent, in a sub-step of the process. According to an exemplary embodiment, the additive can be dissolved in a solvent, for example, water, and used as a liquid stream in the wet scrubber. This allows the addition of the additive to be controlled automatically. Furthermore, the additive can be added manually to the resulting wet waste or, alternatively, fed into the wet waste via a pipe. For this purpose, the additive can, for example, consist solely of the salt of carbonate and / or halide anion.

[0069] According to a further embodiment of the process, the waste products are processed by briquetting, with the additive being added prior to briquetting. Even with this type of post-treatment, the additive can contribute to reducing the tendency to self-ignition. This can apply to a period prior to briquetting, during which the waste products are at least partially in dust form.

[0070] According to a further embodiment of the method, the processing tool is designed as a grinding wheel, brush wheel, polishing wheel, cutting tool, or blasting system. As already explained, a preferred surface processing within the meaning of this disclosure is industrial grinding, cutting, brushing, blasting, or polishing. For this purpose, polishing wheels, milling tools, turning tools, brush wheels, blasting systems, or grinding wheels are used as processing tools. Furthermore, other cutting tools can be used as processing tools.

[0071] According to a further embodiment of the method, the additive is introduced and / or applied into or onto the grinding wheel, brush wheel, cutting tool, or polishing wheel. Within the scope of this disclosure, this can be achieved, for example, by impregnation in the additive. This impregnates, in particular, the carrier material with the additive. Another possibility is to coat the additive onto the grinding, brush, or polishing wheel or the cutting tool. Here, too, the carrier material is the carrier of the additive, but in this embodiment, the additive is increasingly located on the outermost layer of the carrier material of the machining tool. For this purpose, the additive is present as a solution, so that, in addition to the salt, other additives and liquids are present.If the surface treatment involves blasting, where blasting material is accelerated onto the surface to be treated using compressed air, the additive can also be mixed with the blasting material.

[0072] In a further preferred embodiment, the additive can also be incorporated into the material during the production of the carrier material. This is particularly preferred if the carrier material is made of synthetic materials, such as synthetic fibers.

[0073] According to a further embodiment of the method, the abrasive agent is a polishing agent, brushing agent, blasting material, a cutting material, or grinding medium. Polishing agents, brushing agents, or grinding media typically consist of greases, oils, and the actual abrasive agent, such as the abrasive grains. Abrasive grains and also the blasting material can consist of, for example, alumina, corundum, aluminum oxides, aluminum hydroxides, aluminum silicates, magnesium aluminum silicates, chromium trioxides, calcium carbonates, cerium oxides, quartz, iron oxides, silica, or similar materials. Depending on the intended application, the abrasive grains can range in size from approximately 0.1 µm (micrometers) to approximately 200 µm. The abrasive grains can constitute a mass fraction of approximately 20% to 70% of the abrasive agent. Cutting materials typically include cemented carbide, tool steel, cutting ceramics, boron nitrides, or diamond.

[0074] According to a further embodiment of the process, the polishing agent is designed as a solid paste or emulsion. Emulsions for surface treatment typically consist of a mixture of water, fats, oils, and abrasive grain (usually based on ceramic materials), which is ideally evenly distributed throughout the emulsion. The emulsions can be applied through spray nozzles and sprayed onto polishing tools. Solid pastes for surface treatment represent a second essential group of abrasives or polishing agents. These solid pastes are typically mixtures of lipids (including, for example, fats, oils, and waxes), additives mixed with them, and a corresponding proportion of abrasive grain, which is ideally evenly distributed throughout the carrier material.

[0075] According to a further embodiment of the process, the additive is added to the polishing agent. This also ensures that the tendency of the resulting waste product to self-ignite is reduced. In one exemplary embodiment, the active carbonates and / or halogen anions enter the waste stream as a waste product in the form of used polishing agent, along with the other waste products. In the waste stream, the ions can react with the metals to form unreactive compounds, thus also reducing the tendency to self-ignite. The effect of reducing the tendency to self-ignite by using polishing agents has been demonstrated through experiments.

[0076] This exemplary embodiment is advantageous because it allows surface treatment to be automated without the need for additional steps involving the addition of the additive, for example, to the waste products or waste. The additive is already contained in the abrasive agent.

[0077] However, the additive can also be added in other ways, for example according to the exemplary embodiments described above.

[0078] According to a further embodiment of the process, the salt is present in the abrasive agent at less than 10 wt.%, preferably less than 5 wt.%, particularly preferably less than 2.5 wt.%, but greater than 0.01 wt.%. Experiments have shown that even small amounts of salt can be sufficient to reduce the waste's tendency to self-ignite. Furthermore, these amounts do not impair the effectiveness of the abrasive agent, or only impair it insignificantly. This allows identical or at least approximately the same surface treatment results to be achieved as with abrasives without the corresponding salts.

[0079] The object of the invention is further achieved by the use of an additive which contains a salt of a carbonate and / or a halogen anion, preferably a fluoride, for reducing a tendency of wet waste products to self-ignite.

[0080] In this way, the object of the invention is also completely achieved.

[0081] As already explained above, waste products containing flammable substances, especially metal dust, can ignite spontaneously and cause fires and possibly even explosions. The solution of converting metals into non-reactive compounds can be extended analogously to other waste products according to this exemplary embodiment. Waste products can be, for example, those generated during metal processing. These are wet wastes, or wastes that contain a liquid medium, allowing the chemical reaction to form the non-reactive compound to take place.

[0082] According to another exemplary embodiment of the use, the waste products are polishing waste, brush waste, blasting media waste, machining waste, or grinding waste, generally waste from surface processing. The waste typically contains residues of a polishing agent, brush media, blasting media, cutting material, or abrasive, as well as material removed from the machined workpiece, in particular metal chips or metal dust.

[0083] According to one exemplary embodiment, the salt contains a carbonate and / or a halogen anion. Preferably, the halogen anion is a fluoride. According to further exemplary embodiments, the salt is selected from the group consisting of sodium carbonate, potassium carbonate, sodium fluoride, and combinations thereof.

[0084] According to a further embodiment of the use, the waste products arise in at least one partial step of the disclosed process.

[0085] Furthermore, an agent for surface treatment of a workpiece is disclosed herein, wherein the surface treatment agent contains a self-ignition-inhibiting additive, and wherein the self-ignition-inhibiting additive is a salt of a carbonate and / or a halogen anion, preferably a fluoride. In particular, it can be a polishing agent, brushing agent, blasting material, cutting material, or abrasive.

[0086] In this way, the object of the invention is also completely achieved.

[0087] The surface treatment agent can, for example, be solids, a paste (solid paste), or an emulsion. According to an exemplary embodiment, the surface treatment agent further contains abrasive grains, in particular ceramic abrasive grains, and lipids, wherein the lipids are selected from the group consisting of fats, oils, and waxes. The surface treatment agent can also contain water. Other components are conceivable and familiar to the person skilled in the art, such as additives.

[0088] The surface treatment agent can be used in the disclosed process to reduce a tendency of the waste product to self-ignite.

[0089] Further features, characteristics, and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the drawings. These embodiments are purely illustrative and do not limit the scope of the invention.

[0090] Reference is made to the accompanying figures, in which the following is shown. Fig. 1 illustrates an exemplary embodiment of a method for surface treatment of workpieces using a block diagram; Fig. 2 shows the results of an exemplary calorimetric measurement (ARC measurement) with potentially suitable additives using a graph; Fig. 3 shows the results of another ARC measurement with further variations regarding the additive using a graph; Fig. 4 shows the results of another ARC measurement with further variations regarding the additive using a graph; Fig. 5 shows the results of another ARC measurement with further variations regarding the additive using a graph; and Fig. 6 shows the results of another ARC measurement with further variations regarding the additive using a graph.

[0091] Fig. 1illustrates, using a block diagram, an exemplary embodiment of a method for surface treatment of workpieces. In particular, the method can comprise material-removing and / or material-leveling grinding, brushing, blasting, machining, or polishing of metallic workpieces.

[0092] According to step S10, the method comprises providing a processing tool, in particular a grinding wheel, brush wheel, blasting system, cutting tool, or polishing wheel. The processing tool is, for example, disk-shaped and mounted on a spindle coupled to a drive. The processing tool is designed to receive a surface processing agent. For this purpose, the processing tool can be designed to be at least partially absorbent and / or porous. The processing tool can contain, for example, fibers, fabrics, and / or sponge-like materials.

[0093] A further step S12 relates to the provision of an abrasive agent for surface treatment. In particular, this can be an abrasive, brushing agent, blasting material, cutting material, or polishing agent. The agent can be designed, for example, as a solid, solid paste, or emulsion. The agent typically comprises abrasive components, such as abrasive grains, cutting materials, or blasting material, which can be embedded in a carrier material, such as a lipid-based carrier material. Step S12 can further comprise applying the agent to the processing tool provided in step S10. This can be done manually or automatically. Depending on the type of surface treatment agent, the application can comprise spraying, pouring, pressing, and similar processes.

[0094] A further step S14 comprises feeding a workpiece with a surface to be machined. The workpiece is at least partially metallic and in particular made of light metals or non-ferrous metals, such as aluminum, magnesium, zinc, titanium, or alloys containing aluminum, magnesium, titanium, and / or zinc. The feeding can comprise automated or manual feeding. Typically, the workpiece is fed onto a machining tool that is stationary but coupled to a drive. However, this does not preclude the machining tool from being fed onto the workpiece according to alternative exemplary embodiments. In general, step S14 can comprise a relative movement between the workpiece and the machining tool.

[0095] In addition to workpiece-guided machining, tool-guided machining is also conceivable. Here, the workpiece is mounted in a suitable holder and then machined by a multi-dimensionally pivoting tool head; thus, "feeding" is to be understood relatively. In other words, this can involve either tool-guided or workpiece-guided machining.

[0096] This is followed by step S16, which comprises the actual surface treatment of the workpiece. This involves removing material from the workpiece, in particular chips or other small particles that can form dust. Furthermore, abrasion of the processing tool regularly occurs during processing, for example in the form of fiber residues, in particular cotton scraps or dust. In addition, further waste is generated which can be traced back to the surface treatment agent. On the one hand, this can concern a part of the agent that was not involved in the actual processing but was thrown off by the processing tool. Furthermore, it can concern partial quantities of the surface treatment agent that have come into contact with the workpiece. The waste generated during surface treatment therefore comprises various components.

[0097] Waste products generated during surface processing are processed by wetting in a step S18. This can involve removing the waste from the actual processing location. This can be done, for example, using continuously operating extraction systems. However, waste products that are not extracted regularly often remain at the processing location. These waste products can be removed mechanically, for example, manually through regular cleaning. According to at least some exemplary embodiments, step S18 involves treating the waste products in a wet separator. Other types of waste treatment and waste processing are conceivable. For example, it is not uncommon for the waste products to be temporarily stored, for example to collect sufficiently large quantities that can then be disposed of.

[0098] An example of waste processing involves briquetting the waste. This involves compressing the waste and thus dewatering it, while simultaneously removing oxygen from the waste. Additional binding agents are often added to the waste in this context.

[0099] A further step, S20, concerns the disposal of waste products. This requires specialized knowledge and specific processes, so it is often carried out by qualified external companies.

[0100] Both during and after processing, there is a fundamental risk of spontaneous combustion of the waste or a fire caused by external ignition. This could theoretically even occur at the processing site itself. However, this risk has been significantly reduced by safety regulations, such as the use of extraction systems. However, it has been observed in several cases that collected waste is prone to spontaneous combustion. The risk of this generally increases with the amount of waste and the storage period, as well as the associated evaporation of water. Other influencing factors have already been discussed above.

[0101] Within the scope of the present disclosure, it is proposed to add or mix an additive in at least one partial step of the process, which ultimately reduces the tendency of the waste to self-ignite.

[0102] Steps S22, S24, and S26 each concern the addition of the additive. Steps S22, S24, and S26 represent various options for adding the additive. Steps S22, S24, and S26 can be implemented. However, this does not preclude the use of two or more of steps S22, S24, and S26 for adding the additive. It is essential that the additive is detectable at least after the waste products have been processed (step S18).

[0103] The additive can, for example, be added according to step S22 during the preparation of a machining tool (step S10). It is thus conceivable to treat the machining tool accordingly. The additive can, for example, be introduced into the resulting waste via the wheel abrasion generated during machining, which forms a component of the waste. However, the additive can also be dissolved in the solvent used in the processing of the waste products.

[0104] The additive can also be added, for example, according to step S24 as part of the provision of the surface treatment agent (step S12). In other words, the agents used, such as abrasives, brushes, blasting media, cutting materials, or polishing agents, can be provided with the additive. The surface treatment agent forms a component of the resulting waste, so that the additive can ultimately be available there to reduce the reactivity of the waste, in particular of metal chips and metal particles in the waste.

[0105] Furthermore, the additive can be introduced into the waste, for example, according to step S26 during the waste processing (step S18). This can involve mixing the waste with the additive. The additive can also be added during the briquetting of the waste products. Examples of implementation

[0106] During surface treatment, especially polishing, various polishing agents are used, depending on the material, the desired surface quality, and other factors. The resulting waste includes, for example, residues of the polishing agent, cotton fibers from the polishing wheels, and the metal particles abrasion from the material. This waste is extracted, for example, by vacuum, passed through wet separators, and then stored. During storage, spontaneous combustion of the waste sometimes occurs, which may require the intervention of the fire department to control.

[0107] It has been shown that the trigger for this spontaneous combustion is the reaction heat associated with the oxidation of abraded light metal particles. In the experiments described below, we investigated which additives are suitable for suppressing or at least mitigating this reaction.

[0108] Accelerating Rate Calorimetry (ARC) was used as the measurement method. Accelerated Rate Calorimetry (ARC) is a thermoanalytical method in which a sample is stored in a controllable furnace. The temperature of the sample is measured and the furnace is adjusted to the sample temperature, ensuring that no heat flow occurs from the sample to the furnace or vice versa. Thus, at least approximately adiabatic conditions are achieved.

[0109] In this way, the situation inside a large sample can be simulated, where heat loss to the environment through conduction is almost zero and heating occurs exclusively through chemical reactions within the sample. Since the rate of chemical reactions is temperature-dependent, the resulting reaction heat increases the reaction rate and thus the heating inside the sample. Thus, a self-reinforcing effect occurs, potentially leading to accelerated heating.

[0110] During a measurement, the sample is first brought to a defined starting temperature and held there. If no temperature increase is detected within a given time frame, the oven temperature is increased by a specified amount, and the sample is then also monitored for a temperature increase. This process is continued until the sample exhibits self-heating.

[0111] From this point on, the furnace automatically adjusts to the actual sample temperature. This process continues until either the self-heating ceases (e.g., due to complete reaction) or the upper pressure or temperature limits are reached.

[0112] The measurement is plotted as self-heating (SHR) in °C / min) against temperature (in °C). The curve shape can be used to determine whether the heating is accelerated and at what temperature it begins. 1. Preliminary work

[0113] In an initial experiment, the aim was to determine which compounds were suitable for reducing the tendency of polishing agent waste to self-ignite. The salts sodium fluoride and sodium carbonate were initially chosen as potentially suitable candidates.

[0114] The raw material used was real polishing waste generated during the surface treatment of aluminum-containing workpieces. During the surface treatment process, the resulting waste products were collected without prior processing. The waste was therefore not processed in a wet scrubber and was therefore largely dry.

[0115] The first tests included preparatory work according to the following steps before an ARC measurement was carried out: 1. Dissolve the appropriate salt (amount in % based on 10 g of polishing waste) in 200 ml of deionized water; 2. Stir in 10 g of polishing waste, let stand, and stir again; 3. Allow the salt to act (usually for 24 h); 4. Filter off the polishing waste and wash with distilled water; 5. Dry for 24 h in a fume hood at room temperature; and 6. Store in a desiccator under a molecular sieve until the ARC measurement.

[0116] In this case, step 1 in conjunction with step 2 simulates processing in a wet scrubber, which is commonly used in surface treatment. Accordingly, the findings are also applicable to waste that has passed through a wet scrubber.

[0117] In Fig. 2 The results of the experiments are presented. All salts (NaF, Na 2 CO 3 ) exhibit lower self-heating compared to water (served as a reference). Self-heating of the reference is visible above 230°C. This first experiment demonstrated that sodium carbonate and sodium fluoride, used as additives, can reduce the tendency of waste to self-ignite. It was impressively demonstrated that hardly any measurable, potentially critical self-heating of the samples could be observed in the selected concentration ranges.

[0118] In addition to the ARC measurement, a DSC (differential scan calorimetry) measurement was performed in parallel (not shown in the figures). This showed that all salts reduce the energy content (J / g) of the peak (reference approx. 200 °C). In addition, the onset temperature, i.e., the temperature at which an exotherm occurs, is increased.

[0119] Based on these findings, further tests were conducted with sodium carbonate and sodium fluoride. Different additive concentrations and exposure times were investigated. 2. Variation of the concentrations and exposure times of the salts

[0120] In a second experiment, the effect of different concentrations and exposure times of the salts on the waste was investigated. The experiment was carried out in a similar way to that described in section 1.

[0121] The results of this ARC measurement are shown in Fig. 3 shown.

[0122] Fig. 3 provides a comprehensive overview of the various self-heating processes of the samples. All samples treated with the disclosed additives exhibit lower self-heating than the untreated sample. In the range from 230 °C, a 1% NaF sample with an exposure time of 86 hours exhibits greater self-heating than a 1% Na 2 CO 3 sample with an exposure time of 72 hours. In addition, the 10% Na 2 CO 3 sample with an exposure time of 6 hours also exhibits greater self-heating than the aforementioned 1% Na 2 CO 3 sample with 72 hours. This demonstrates not only the influence of the salt concentration but also the influence of the exposure time.

[0123] To clearly separate these influences, the NaF and Na 2 CO 3 samples were repeated with identical exposure times of 24 hours. These results are presented in Fig. 4 Compared to the reference, self-heating is reduced to 56.5% (carbonate) and 39.1% (fluoride). 3. Polishing agent containing a salt of carbonate / halogen anion

[0124] Based on the findings from the experiments described above, a modified polishing emulsion containing the salts sodium fluoride, sodium carbonate, and potassium carbonate was prepared in the next step. Polishing tests were conducted with these polishing agents using a robot. The resulting waste was processed in a wet scrubber to obtain the polishing waste in wet form. The tests included the following steps before an ARC measurement was performed: 1. Stir 10 g of polishing waste into 200 ml of distilled water, let stand, and stir again; 2. Let the solution stand for 24 h; 3. Filter off the residue and wash with distilled water; 4. Dry the residue for 24 h in a fume hood at room temperature; and 5. Store in a desiccator under a molecular sieve until the ARC measurement.

[0125] The results of these experiments are presented in Fig. 5 shown.

[0126] The experiments show that sodium fluoride is less effective in this setup than the various carbonates. Furthermore, the curves for the reference and fluoride samples become steeper towards the end with increasing temperature, while the carbonates show a somewhat flatter curve towards the end. Consequently, self-heating could be inhibited and possibly even stopped at higher temperatures.

[0127] Therefore, in a further experiment, the reference was mixed with 1 or 2 wt.% sodium carbonate and examined. Fig. 6All carbonate samples are summarized. A clear decrease in the tendency to self-ignition can be seen from the reference to the samples with 1 wt.% carbonate. The sample with 2 wt.%, in addition to the lower self-heating, also exhibits a peak at approximately 270°C, above which the self-heating decreases again. This sample does not exhibit self-accelerated heating. Based on these measurements, a higher additive concentration (e.g., 2% instead of 1%) is preferable in terms of inhibiting properties. 4. Summary

[0128] In experimental trials, fluoride and carbonate proved to be suitable additives. When incorporated directly into the formulation, carbonate exhibits a better effect than fluoride, which appeared more suitable in preliminary tests with older polishing agent waste. The choice of cation (sodium or potassium) does not appear to have any influence on the additive's inhibiting effect and can be optimized during formulation work. Higher additive concentrations have a positive effect on the waste's safety by reducing self-heating.

[0129] Furthermore, it has been shown that the tendency to self-ignite can also be reduced in waste generated during blasting or machining processes. This waste typically consists primarily of metal dust or chips, blasting grit, and water. By adding the additive, the metals react, thus largely limiting the formation of highly flammable hydrogen, thus reducing the tendency to self-ignite in this waste as well.

Claims

1. Method for the surface treatment of workpieces by means of abrasive media, comprising the following steps: - providing a treatment tool; - providing an abrasive medium; - supplying a workpiece having a surface to be treated; - surface treating the workpiece, involving depletion of material, wherein waste products are formed; and - processing the waste products, by wetting of the waste products; wherein at least one of said steps comprises the following: - adding an additive to lower a self-ignition tendency on the part of the waste products, the additive comprising a salt, composed of a carbonate and / or of a halogen anion.

2. Method as claimed in claim 1, wherein the workpiece surface to be treated consists of magnesium, magnesium alloys, aluminum, aluminum alloys, titanium, titanium alloys, zinc or zinc alloys.

3. Method as claimed in claim 1 or 2, wherein the salt is selected from the group consisting of sodium carbonate, potassium carbonate, and sodium fluoride.

4. Method as claimed in any of the preceding claims, wherein the salt comprises a fluoride.

5. Method as claimed in any of the preceding claims, wherein the processing of the waste products is carried out in a wet separator, involving the formation of wet waste, the additive being added preferably within the wet separator and / or to the wet waste.

6. Method as claimed in any of the preceding claims, wherein the processing of the waste products comprises briquetting, and wherein the additive is added before the briquetting.

7. Method as claimed in any of the preceding claims, wherein the treatment tool is configured as a grinding disk, brushing disk, polishing disk, machining tool or blasting system.

8. Method as claimed in any of claims 1 to 6, wherein the treatment tool is configured as a grinding disk, brushing disk, machining tool or polishing disk, and wherein the additive is introduced into and / or applied to the grinding disk, brushing disk, polishing disk or machining tool.

9. Method as claimed in any of the preceding claims, wherein the abrasive medium is a polishing composition, brushing composition, blasting medium, cutting material or grinding composition, with the additive being added preferably to the polishing composition, brushing composition, blasting medium, cutting material or grinding composition.

10. Method as claimed in any of the preceding claims, wherein the salt is present at less than 10 wt%, preferably less than 5 wt%, more preferably less than 2.5wt%, but greater than 0.01 wt% in the abrasive composition.

11. Use of an additive which comprises a salt composed of a carbonate and / or of a halogen anion for lowering a self-ignition tendency on the part of wet waste products from surface treatment, particularly of polishing cases, brushing wastes, blasting medium wastes, grinding wastes or machining wastes.

12. Use as claimed in claim 11, wherein the salt is selected from the group consisting of sodium carbonate, potassium carbonate, sodium fluoride.