The task of quickly and efficiently cleaning the surface of any material is of great importance in a variety of fields of activity. For example, this is extremely necessary in car service workshops that paint cars: after preliminary preparation of the body, the paint adheres better and lasts longer. It is also impossible not to mention the need to clean metal workpieces from traces of corrosion in industry, remove scale and slag from welds, and much more. To carry out work with high productivity and at the same time achieve acceptable economic efficiency, you need to choose the right abrasive for sandblasting.
Abrasive Differences
An abrasive is a hard material with a rough surface used for abrading and polishing various substrates. Most abrasives come in fine powder form, but some include larger particles with sharp edges. Despite the existence of different types of abrasives, they are all characterized by a common property: they have sufficient hardness, therefore they are able to clean metal surfaces, concrete slabs and other materials from contamination.
When used in a sandblaster, abrasive particles are blown outward by a powerful air stream. The device gives them greater kinetic energy, as a result of which the existing plaque is quickly cleaned off. All abrasives are divided into:
- natural (sand, corundum, spar, diamond, chalk, iron ore, etc.);
- synthetic (couproslag, borazone, boron carbide, etc.).
They differ in origin and composition, degree of hardness, mechanical and chemical resistance. The most popular and inexpensive is quartz sand for sandblasting. Before going on sale, sand goes through several stages of processing, otherwise it can damage equipment. Abrasives also differ in particle size: for example, for delicate or damaged substrates, you need to choose the most gentle materials.
Hardness
All abrasives based on hardness - the ability to resist pressing other material into them - are divided into:
- superhard;
- hard;
- soft.
Even soft materials can remove dirt, but are more gentle. The hardness index is established according to the developed Mohs mineralogical scale, dividing abrasives into 10 classes. This division implies an increase in hardness as the class increases (the softest - talc - has class 1, the hardest - diamond - class 10).
Fraction
Abrasive materials for grinding surfaces differ in grain size (fineness), depending on which they are assigned certain numbers:
- fine micropowders (M10–M5);
- micropowders (M63–M14);
- grinding powders (12–3);
- grinding grain (200–15).
In other words, according to their fraction, abrasives are divided into coarse (coarse), medium, fine and extra fine. To produce them, the base material is crushed by a press, resulting in the formation of crumbs. It is sifted through special sieves and separated into powder with different grain sizes, individual crystals or fragments. Typically, abrasives of the coarsest fraction are used to clean materials from a thick layer of plaque, and the fine fraction is intended for final polishing.
Abrasive ability
By abrasive ability we mean the time period during which it is possible to clean a certain area of the product. This is the amount of material that can be sanded per unit of time. This property strongly depends on the size, hardness and other physical properties of the crystals. Also, the abrasive ability is determined by the intensity of the breakup of particles into acute-angled elements during grinding.
Mechanical stability
Different types of abrasives differ in their ability to withstand loads without destruction. Mechanical resistance depends on the compressive strength. The latter is detected by applying pressure to a crystal of an abrasive material and measuring the load at the moment of its destruction. For most abrasives, mechanical stability decreases as the ambient temperature increases. The higher the durability rating, the more times the abrasive can be reused.
Chemical resistance
This property reflects the ability of abrasive materials not to change their basic qualities under the influence of aggressive chemicals (acids, solvents, alkalis), as well as water.
Content:
Types of sand for sandblasting Features of all types For what type of work is sandblasting sand suitable? Correct selection of sand How to prepare sand on your own?
Sandblasting surface cleaning is a technology that dates back to the 19th century. Then a pneumatic apparatus was invented that cleaned metal structures of dirt, old paint, varnish or rust with a jet of sand flying out of a nozzle under high pressure. Already in the middle of the 20th century, it became clear that sand does not always cope with surface treatment, and other effective materials suitable for use in sandblasting were found. At the same time, experts realized that sand, crushed upon impact with the surface to the state of dust, enters the lungs. This causes a fatal disease in humans - silicosis. And although the person working with sandblasting must be protected by a special suit and a respirator, sand dust can spread over a long distance and enter the lungs of a bystander. Sand is also not the hardest abrasive material, which means it can't clean all surfaces. In this case, the material consumption is higher than when using other types of abrasives.
But despite all of the above, sand still remains the most popular consumable material for sandblasting. It has a number of advantages over more modern materials:
- Low strength. On the one hand, this reduces the efficiency of processing, but on the other hand, it ensures that the surface being treated is not damaged during the process.
- When using sand, sandblasting parts wear out less and last longer, since the abrasive effect is much less aggressive.
- Availability. Sand is cheaper than other types of abrasives, which allows significant savings even with large material consumption.
- Budget option. With certain preparation of the material, almost any sand will be suitable, which significantly reduces the cost of the processing process.
- The ability to select the desired sand size to achieve a certain abrasive effect. Now you can find sand with a wide variety of grain sizes, which will allow, on the one hand, to achieve the desired result, and on the other, to ensure that the surface is not damaged.
Different types of sand are suitable for working with different materials. If you want to know what kind of sand to use for sandblasting, you first need to decide what types of sand are intended for such work.
Types of abrasives
When selecting sand for a sandblasting gun or another type of abrasive, you need to take into account the basic properties and characteristics of the latter in order to carry out the work with maximum efficiency.
Quartz sand
It is quartz sand that is most in demand on the market for sandblasting and grinding products. It is characterized by a low price, decent quality, and is sold everywhere. Quartz sand is made from white quartz by crushing it into different fractions:
- up to 0.1 mm;
- 0.10–0.4 mm;
- 0.5–1 mm;
- more than 1 mm.
The sand undergoes thorough screening, so larger particles are practically not found in its small fractions, and sandblasting can be done without harm to the product. The material has good durability and abrasive ability, especially considering its availability. Sand will not damage delicate products or non-ferrous metals. Waste quartz sand after sandblasting can be sold as a building material.
A significant disadvantage of sand is the release of a large amount of dust, which enters the worker’s lungs and eyes, which is harmful to his health. With the regular use of sand for such grinding in the absence of personal protective equipment, a deadly disease can develop - silicosis. To avoid such problems, all equipment should be equipped with dust removal systems, and each batch of sand should be used no more than 1-2 times.
Cooper slag and nickel slag
These abrasive materials are obtained by processing slag from nickel and copper production. They are considered reusable, economical and more effective than quartz. The particle strength, hardness and abrasive ability of cooper slag is higher than that of nickel slag. Such materials can be used up to 3 times without the risk of dust.
The use of these abrasives is advisable when cleaning expensive and complex structures, which is associated with the high quality of the result, but also with the price of materials. Cooper slag and nickel slag are capable of cleaning the most durable types of metal and concrete; they do not crush along with plaque due to their high strength.
Metal (technical) shot
This material is small metal balls made from steel or cast iron. Technical shot can be cast, chopped, chipped, with the first having a spherical shape, and the rest being acute. Steel and cast iron shots are used for shot blasting and shot blasting of products that require notching (profiling) or descaling. This purpose is associated with the high strength of the materials and the presence of sharp-angled edges on their particles. After treatment, the metal base will have a high degree of adhesion and adhere perfectly to finishing coatings.
Steel shot is of good quality - it is the hardest, has the highest strength characteristics, can be used several times, and does not cause dust. The increased service life is due to additional heat treatment of the shot during its production. Stainless steel shot is used for processing structures made of the following materials:
- steel;
- zinc;
- titanium;
- aluminum;
- copper;
- bronze;
- brass;
- concrete;
- granite;
- marble.
Corundum
This material is prepared on the basis of aluminum oxide and is considered one of the most durable abrasives. Its particles are in the form of crystals, and their characteristics are close to diamond. The price of the material is high, which is why it is used for processing mainly expensive products. Corundum can be reused many times. It is ideal for decorative sanding and polishing of surfaces.
A variety of corundum is electrocorundum - a super-strong material obtained by adding a number of impurities to aluminum oxide. Its particles are not damaged at all during processing of materials, therefore repeated processing can be carried out a large number of times (after sifting). On the Mohs scale, electrocorundum is only one position inferior to diamond, it is so hard. Its grains have sharp edges and have the unique ability to sharpen themselves.
Garnet sand
Garnet, or garnet sand, is an abrasive of mineral origin, which in terms of technical characteristics is superior to quartz sand, nickel slag, and cooper slag. The material can be used repeatedly, used both for sandblasting and for hydraulic cutting of metal.
What parameters should be considered when purchasing sand?
An important condition for purchasing a high-quality abrasive is the possibility of its reuse and a minimum amount of dust in the composition. Due to safety precautions, it is prohibited to use sand without personal protective equipment and special dust extractors, because when it hits the surface, the abrasive will still break into dust. Therefore, if it is not possible to carry out work in accordance with the standards, preference will have to be given to another type of abrasive material.
To select the sand of the right category, you should consider the following recommendations:
- Plaque thickness. The larger it is, the larger the sand fraction should be. A dense, thick layer of rust can only be cleaned using a coarse abrasive - grinding grain.
- Base hardness. The harder the material of the product that needs to be cleaned, the stronger the abrasive should be.
- Purpose of processing. When it is necessary to obtain a smooth surface even without minor defects, choose the finest sand. On the contrary, coarse grains are required to create a network of scratches and enhance adhesion to protective coatings. Typically, sand with a fraction of 0.6–1 mm is used to remove rust, and larger ones are suitable for removing thick bitumen coatings.
- Speed of sandblasting machine. At high speed, the soft abrasive particles will be quickly destroyed and the work efficiency will remain low. Also, at high speeds, using rounded particles will be less effective than those with sharp edges.
Can sandblasting be done with regular sand?
Sand is a sedimentary rock of natural origin or an artificial material created from it. Despite the permissibility of using ordinary sand for sandblasting equipment, it is impossible to perform high-quality processing in this way. This is due to a number of reasons:
- leaving dust on the treated surface;
- ability to mask corrosion;
- content in the composition of salt deposited on the workpieces;
- negative impact on equipment, contributing to the formation of blockages.
Important!
In the Russian Federation and Europe, legislation officially prohibits the use for sandblasting of sand whose free quartz content exceeds 1%.
The use of ordinary sand is an uneconomical solution, since the material quickly becomes unusable and cannot be reused. Surface treatment using sandblasting technology is considered an effective method for getting rid of corrosion, scale and various contaminants. To achieve a positive result, the main thing is to choose the right material for the equipment.
Areas of application of abrasive materials
The area of use of abrasives may vary depending on their type, strength, cost, and fraction. For example, river or quartz sand is most often used to remove paints, rust, and dirt from building facades and metal bases. To polish products made of copper, aluminum and similar materials, use quartz sand with a particle size of 0.1–0.3 mm; to clean metal from stubborn paint, it is better to take a sand fraction of 0.3–0.6 mm.
Old traces of rust, which are difficult to remove chemically, are removed by sandblasting using 0.6–1.6 mm sand or nickel slag or cooper slag. The same abrasives can be used to remove welding scale from metal structures. Technical shot is most often used for cleaning:
- small, medium, heavy casting;
- rolled carbon and stainless steel;
- products subject to painting, electroplating;
- car body parts.
During processing, shot also helps to strengthen torsion shafts, coil springs, and spring leaves. Electrocorundum, corundum is used for cleaning and grinding titanium, alloy steel, and tempered glass.
What is sandblasting
The sandblasting technique was patented in 1870 by American inventor Benjamin Tillman. If we describe the technology in simple words, we can imagine the surface treatment process as follows:
- an abrasive powder is selected that is specially created or suitable for solving a particular problem;
- a pneumatic compressor acts as a source of energy;
- sand, flying at enormous speed from a specially designed nozzle along with air, hits the surface being treated with force.
As a result of this effect, any dirt and coatings are removed from metal, wood, and plastic.
The highest economic efficiency of application and achieved processing results are offered by simple and common materials. In particular, the usual sifted river sand can be successfully used for sandblasting. In this case, it is possible in a certain way to select, so to speak, the characteristics of the working fluid (for example, particle size) to obtain the desired operating speed and final surface indicators.
However, if you take sand to use with a sandblasting machine, you should understand that this material has both advantages and disadvantages. The latter are so significant that processing with such an abrasive is prohibited in some countries at the legislative level.
Making abrasives at home
In some cases, you have to prepare your own consumable mixture for sandblasting, for example, in order to save money. Homemade abrasive is well suited for cleaning metal and concrete bases. Typically, gravel or river sand is used as the starting material. The order of work is as follows:
- prepare 2-3 sieves made of fine mesh stretched over a wooden frame;
- sift the sand first to remove debris through a sieve with larger cells, then through smaller ones until the required abrasive fraction is obtained;
- the finished material is dried in a metal container over a fire or in another way;
- sift the sand again through a sieve with the smallest mesh.
Such sand can be poured into a sandblasting gun or device of a different design and used for its intended purpose.
Necessary equipment, devices
Industrial equipment for sandblasting consists of:
- main compressor supplying compressed air to the nozzle;
- an abrasive blasting machine that adds sand to the working hose;
- a sleeve through which air and sand flow;
- nozzle;
- an additional compressor supplies air to the worker’s protective suit;
- air filter.
The pressure produced by the compressor determines the power of the entire sandblasting unit. An abrasive blasting machine mixes air with sand in various ways:
- injection;
- gravitational;
- suction
An additional low-power compressor supplies air through a filter under the protective suit mask, providing the worker with the opportunity to breathe normally. Sandblasting guns are available for small jobs and home use. They have a power of 3-5 Atm and are equipped with a compact compressor. A small amount of metal stripping is carried out in a respirator.
Where can I get sand for sandblasting?
Sand is sold at any hardware store. There is packaged material on sale in bags - regular without division into fractions or already purified and sifted with the particle size indicated on the packaging. Most often, quartz sand is sold in 25 kg bags, its price per package is 250–300 rubles. Purified and fractionated river sand is cheaper (150–180 rubles per 25 kg), while unseeded sand costs between 50–60 rubles per bag. For comparison, the cost of garnet sand is about 700 rubles/25 kg, and electrocorundum is up to 2300 rubles for the same volume.
Consumption of quartz sand during sandblasting
Abrasive consumption varies greatly depending on the specific treatment and is determined by the power of sandblasting, the volume of work, the fraction, the degree of contamination of the base, the size of the nozzle and other parameters. It is advisable to identify the expense indicator at the initial stage in order to calculate the total financial costs for the entire work. The best choice will be an abrasive that will have a minimum cost per unit area.
A good economic effect comes from using sand for sandblasting if its fraction is ideal for a particular type of work, and cleaning is carried out in a special box. The exact consumption may change along with the original data (for example, with different thicknesses of the rust layer on one product), and the calculations will be approximate in any case.
An example of calculating abrasive for metal processing per 1 square meter
To understand which abrasive is best suited for processing, it is worth considering the average consumption of the most popular materials when cleaning metal to a degree of Sa 2½:
| Abrasive name | Consumption, kg/sq. m |
| Quartz sand | 60–110 |
| Nickelslag | 35–80 |
| Cooper slag | 35–80 |
| Garnet | 3–7 |
| Electrocorundum | 3–10 |
| Technical fraction | 5–10 |
On average, 2–3 kg of sand is consumed per minute of processing a metal surface. The consumption of this material can be somewhat reduced by using modern sandblasting machines with a closed processing cycle, as well as vacuum systems for collecting waste abrasive.
When removing old stubborn paint, a thick layer of rust, or stuck dried cement, you will have to spend a lot of time cleaning the already used abrasive, which will have increased dust formation due to accelerated destruction. In such situations, it is worth considering purchasing a different abrasive material with greater hardness.
Selecting consumables
The choice of consumables depends on the surface to be treated. The right solution increases the efficiency and speed of the process, and allows you to reduce costs. When choosing abrasive sand, it is important to pay attention to:
Average prices for abrasives for sandblasting
- thickness of the coated or contaminated layer, its stability;
- on the hardness/softness of the surface;
- requirements for the type of product being processed. If you want something smooth, unwrinkled, and without chips, the choice is crushed sand;
- process pace;
- possibility of secondary use of abrasive.
You should not choose an abrasive of a crushed fraction with low hardness values for a durable and thickened layer: the desired result will not be achieved. For soft substrates, choosing an abrasive sand that is too hard will cause damage. For hard surfaces, an abrasive with a high hardness rating is needed. When working with hard material, the particles of which have sharp edges, high speed sandblasting is ensured. Grains with rounded edges will process the product longer.
Preparation of river sand for sandblasting
As preparation measures, the sand should be thoroughly dried and sifted. It must be completely dry before loading into the sandblaster, otherwise the device may be damaged. The permissible level of humidity is determined by squeezing the material with your hand - it should flow freely through your fingers. The sand fraction must ideally match the size of the nozzle, which is achieved by sifting on sieves with cells of the required size.
How to sift sand for sandblasting?
To clean sand at home, you can use improvised means - tulle, gauze, flour sieve, mosquito net. The main thing is to sift the abrasive several times so that it is of high quality, uniform in particle size and does not include foreign impurities.
How to dry sand for sandblasting?
The easiest way to dry the sand is in a special drum dryer. The installation has a convenient drying chamber and a built-in sieve, so the time and effort required to prepare the abrasive will be minimal. If such a device is not available, you can dry the sand over the flame of a fire. To do this, a sheet of metal, an iron box, or another metal container is fixed above the fire, where the sand will be located. Some craftsmen dry the material using a heat gun, scattering it on film. This is convenient and easy to do, and the quality of the finished abrasive will be at a decent level.
