![Corrosion](https://upload.wikimedia.org/wikipedia/commons/b/b3/Corrosion.Pit.jpg)
Sandblasting, sometimes known as abrasive blasting, is the operation of forcibly propelling a stream of
abrasive
An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away by friction. While finishing a material often means polishing it to gain a smooth, reflec ...
material against a surface under high
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
to smooth a
rough surface, roughen a smooth surface, shape a surface or remove surface
contaminant
Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, workplace, etc.
Types of contamination
Wi ...
s. A pressurised fluid, typically
compressed air
Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air is an important medium for transfer of energy in industrial processes, and is used for power tools such as air hammers, drills, wrenches, and o ...
, or a
centrifugal wheel is used to propel the blasting material (often called the ''media''). The first abrasive blasting process was
patent
A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...
ed by
Benjamin Chew Tilghman
Benjamin Chew Tilghman (18211901) was an American soldier and inventor. He is best known as the inventor of the process of sandblasting.
Early life
He was born in Philadelphia, Pennsylvania, on October 26, 1821, the third child of Benjamin and An ...
on 18 October 1870.
There are several variants of the process, using various media; some are highly abrasive, whereas others are milder. The most abrasive are shot blasting (with metal
shot
Shot may refer to:
Arts, entertainment, and media
* ''Shot'' (album), by The Jesus Lizard
*''Shot, Illusion, New God'', an EP by Gruntruck
*'' Shot Rev 2.0'', a video album by The Sisters of Mercy
* "Shot" (song), by The Rasmus
* ''Shot'' (2017 f ...
) and sandblasting (with
sand
Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of s ...
). Moderately abrasive variants include
glass
Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of ...
bead blasting (with glass
bead
A bead is a small, decorative object that is formed in a variety of shapes and sizes of a material such as stone, bone, shell, glass, plastic, wood, or pearl and with a small hole for threading or stringing. Beads range in size from under ...
s) and plastic media blasting (PMB) with ground-up plastic stock or
walnut
A walnut is the edible seed of a drupe of any tree of the genus ''Juglans'' (family Juglandaceae), particularly the Persian or English walnut, '' Juglans regia''.
Although culinarily considered a "nut" and used as such, it is not a true ...
shells and
corncobs. Some of these substances can cause anaphylactic shock to individuals allergic to the media. A mild version is
sodablasting
Soda blasting is a mild form of abrasive blasting in which sodium bicarbonate particles are blasted against a surface using compressed air. It has a much milder abrasive effect than sandblasting. An early use was in the conservation-restoration ...
(with
baking soda
Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3∠...
). In addition, there are alternatives that are barely abrasive or nonabrasive, such as
ice blasting
Ice blasting is the use of explosives to break up ice in rivers, aiding navigation and preventing flooding.
This is done during the spring when snow is melting and river ice is breaking up. There is always a chance that the ice flows could colli ...
and
dry-ice blasting
Dry-ice blasting is a form of carbon dioxide cleaning, where dry ice, the solid form of carbon dioxide, is accelerated in a pressurized air stream and directed at a surface in order to clean it.
The method is similar to other forms of media bla ...
.
Types
Sandblasting
Sand blasting is also known as abrasive blasting, which is a generic term for the process of smoothing, shaping and cleaning a hard surface by forcing solid particles across that surface at high speeds; the effect is similar to that of using
sandpaper
upright=1.35, Sheets of sandpaper with different grit sizes (40 (coarse), 80, 150, 240, 600 (fine)).
Sandpaper and glasspaper are names used for a type of coated abrasive that consists of sheets of paper or cloth with abrasive material glued to ...
, but provides a more even finish with no problems at corners or crannies. Sandblasting can occur naturally, usually as a result of particles blown by
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ho ...
causing
aeolian erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...
, or artificially, using
compressed air
Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air is an important medium for transfer of energy in industrial processes, and is used for power tools such as air hammers, drills, wrenches, and o ...
. An artificial sandblasting process was
patent
A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...
ed by
Benjamin Chew Tilghman
Benjamin Chew Tilghman (18211901) was an American soldier and inventor. He is best known as the inventor of the process of sandblasting.
Early life
He was born in Philadelphia, Pennsylvania, on October 26, 1821, the third child of Benjamin and An ...
on 18 October 1870.
Thomas Wesley Pangborn perfected the idea and added compressed air in 1904.
Sandblasting equipment typically consists of a chamber in which sand and air are mixed. The mixture travels through a hand-held nozzle to direct the particles toward the surface or work piece. Nozzles come in a variety of shapes, sizes, and materials.
Boron carbide is a popular material for nozzles because it resists abrasive wear well.
Wet abrasive blasting
Wet abrasive blasting uses water as the fluid moving the abrasives. The advantages are that the water traps the dust produced, and lubricates the surface. The water cushions the impact on the surface, reducing the removal of sound material.
One of the original pioneers of the wet abrasive process was Norman Ashworth who found the advantages of using a wet process as a strong alternative to dry blasting. The process is available in all conventional formats including hand cabinets, walk-in booths, automated production machinery and total loss portable blasting units. Advantages include the ability to use extremely fine or coarse media with densities ranging from
plastic
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
to
steel
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
and the ability to use hot water and soap to allow simultaneous degreasing and blasting. The reduction in dust also makes it safer to use siliceous materials for blasting, or to remove hazardous material such as
asbestos
Asbestos () is a naturally occurring fibrous silicate mineral. There are six types, all of which are composed of long and thin fibrous crystals, each fibre being composed of many microscopic "fibrils" that can be released into the atmosphere b ...
,
radioactive
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...
or poisonous products.
Process speeds are generally not as fast as conventional dry abrasive blasting when using the equivalent size and type of media, in part because the presence of water between the media and the substrate being processed creates a lubricating cushion that can protect both the surface and the media, reducing breakdown rates. Reduced impregnation of blasting material into the surface, dust reduction and the elimination of static cling can result in a very clean surface.
Wet blasting of mild steel will result in immediate or 'flash' corrosion of the blasted steel substrate due to the presence of water. The lack of surface recontamination also allows the use of single equipment for multiple blasting operations—e.g.,
stainless steel
Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...
and
mild steel items can be processed in the same equipment with the same media without problems.
Vapor blasting
A variant of wet blasting is vapor blasting (or vapour blasting; U.K.). In this process pressurized air is added to the water in the nozzle producing a high-speed mist, called "vapor". This process is even milder than wet blasting, allowing mating surfaces to be cleaned while retaining their ability to mate.
Bead blasting
''Bead blasting'' is the process of removing surface deposits by applying fine glass beads at a high pressure without damaging the surface. It is used to clean calcium deposits from pool tiles or any other surfaces, remove embedded fungus, and brighten
grout color. It is also used in
auto body
A coachbuilder or body-maker is someone who manufactures bodies for passenger-carrying vehicles.Construction has always been a skilled trade requiring a relatively lightweight product with sufficient strength. The manufacture of necessarily ...
work to remove paint. In removing paint for auto body work, bead blasting is preferred over sand blasting, as sand blasting tends to create a greater surface profile than bead blasting. Bead blasting is often used in creating a uniform surface finish on machined parts. It is additionally used in cleaning mineral specimens, most of which have a
Mohs hardness
The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material.
The scale was introduced in 1812 by t ...
of 7 or less and would thus be damaged by sand.
Wheel blasting
In wheel blasting, a spinning wheel propels the abrasive against an object. It is typically categorized as an airless blasting operation because there is no propellant (gas or liquid) used. A wheel machine is a high-power, high-efficiency blasting operation with recyclable abrasive (typically steel or stainless-steel shot,
cut wire, grit, or similarly sized pellets). Specialized wheel blast machines propel plastic abrasive in a
cryogenic chamber and is usually used for deflashing plastic and
rubber
Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
components. The size of the wheel blast machine, and the number and power of the wheels vary considerably depending on the parts to be blasted as well as on the expected result and efficiency. The first blast wheel was patented by Wheelabrator in 1932.
In
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
, the first blast wheel was built around the 1950s,
Qinggong Machinery is one of the earliest manufacturers of blast wheel.
Micro-abrasive blasting
Micro-abrasive blasting is dry abrasive blasting process that uses small nozzles (typically 0.25 mm to 1.5 mm diameter) to deliver a fine stream of abrasive accurately to a small part or a small area on a larger part. Generally the area to be blasted is from about 1 mm
2 to only a few cm
2 at most. Also known as pencil blasting, the fine jet of abrasive is accurate enough to write directly on glass and delicate enough to cut a pattern in an
eggshell
An eggshell is the outer covering of a hard-shelled egg and of some forms of eggs with soft outer coats.
Diversity
Worm eggs
Nematode eggs present a two layered structure: an external vitellin layer made of chitin that confers mechanical ...
. The abrasive media particle sizes range from 10 micrometres up to about 150 micrometres. Higher pressures are often required.
The most common micro-abrasive blasting systems are commercial bench-mounted units consisting of a power supply and mixer, exhaust hood, nozzle, and gas supply. The nozzle can be hand-held or fixture mounted for automatic operation. Either the nozzle or part can be moved in automatic operation.
Automated blasting
Automated blasting is simply the
automation
Automation describes a wide range of technologies that reduce human intervention in processes, namely by predetermining decision criteria, subprocess relationships, and related actions, as well as embodying those predeterminations in machines ...
of the abrasive blasting process. Automated blasting is frequently just a step in a larger automated procedure, usually involving other surface treatments such as preparation and coating applications. Care is often needed to isolate the blasting chamber from mechanical components that may be subject to
dust fouling.
Dry-ice blasting
In this type of blasting, air and
dry ice
Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily ...
are used. Surface contaminants are dislodged by the force of frozen carbon dioxide particles hitting at high velocity, and by slight shrinkage due to freezing which disrupts adhesion bonds. The dry ice
sublimates, leaving no residue to clean up other than the removed material. Dry ice is a relatively
soft material, so is less destructive to the underlying material than sandblasting.
Bristle blasting
Bristle blasting, unlike other blasting methods, does not require a separate blast medium. The surface is treated by a brush-like
rotary tool
Die grinders and rotary tools are handheld power tools used for grinding, sanding, honing, polishing, or machining material (typically metal, but also plastic or wood). All such tools are conceptually similar, with no bright dividing line bet ...
made of dynamically tuned high-
carbon steel wire bristles. Repeated contact with the sharp, rotating bristle tips results in localized impact, rebound, and crater formation, which simultaneously cleans and coarsens the surface.
Vacuum blasting
Vacuum blasting is a method that generates very little
dust
Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in ho ...
and spill, as the blast tool does dry abrasive blasting and collects used blast media and loosened particles from the surface to be treated, simultaneously. Blast media consumption is relatively low with this method, as the used blast media is automatically separated from dust and loosened particles, and reused several times.
Equipment
Portable blast equipment
Mobile dry abrasive blast systems are typically powered by a diesel air compressor. The air compressor provides a large volume of high pressure air to a single or multiple "blast pots". Blast pots are pressurized, tank-like containers, filled with abrasive material, used to allow an adjustable amount of blasting grit into the main blasting line. The number of blast pots is dictated by the volume of air the compressor can provide. Fully equipped blast systems are often found mounted on
semi-tractor trailers, offering high mobility and easy transport from site to site. Others are
hopper
Hopper or hoppers may refer to:
Places
*Hopper, Illinois
* Hopper, West Virginia
* Hopper, a mountain and valley in the Hunza–Nagar District of Pakistan
* Hopper (crater), a crater on Mercury
People with the name
* Hopper (surname)
* Grace H ...
-fed types making them lightweight and more mobile.
In wet blasting, the abrasive is introduced into a pressurized stream of water or other liquid, creating a
slurry. Wet blasting is often used in applications where the minimal dust generation is desired. Portable applications may or may not recycle the abrasive.
Blast cabinet
![Cabine de sablage arena](https://upload.wikimedia.org/wikipedia/commons/f/f2/Cabine_de_sablage_arena.JPG)
A blast cabinet is essentially a closed loop system that allows the operator to blast the part and recycle the abrasive. It usually consists of four components; the containment (cabinet), the abrasive blasting system, the abrasive recycling system and the dust collection. The operator blasts the parts from the outside of the cabinet by placing his arms in gloves attached to glove holes on the cabinet, viewing the part through a view window, turning the blast on and off using a foot pedal or
treadle
A treadle (from oe, tredan, "to tread") is a mechanism operated with a pedal for converting reciprocating motion into rotating motion. Along with cranks, treadmills, and treadwheels, treadles allow human and animal machine power in the absen ...
. Automated blast cabinets are also used to process large quantities of the same component and may incorporate multiple blast nozzles and a part conveyance system.
There are three systems typically used in a blast cabinet. Two, siphon and pressure, are dry and one is wet:
* A siphon blast system (suction blast system) uses the compressed air to create vacuum in a chamber (known as the blast gun). The negative pressure pulls abrasive into the blast gun where the compressed air directs the abrasive through a blast nozzle. The abrasive mixture travels through a nozzle that directs the particles toward the surface or workpiece.
Nozzles come in a variety of shapes, sizes, and materials.
Tungsten carbide
Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...
is the liner material most often used for mineral abrasives. Silicon carbide and boron carbide nozzles are more wear resistant and are often used with harder abrasives such as aluminium oxide. Inexpensive abrasive blasting systems and smaller cabinets use ceramic nozzles.
* In a pressure blast system, the abrasive is stored in the pressure vessel then sealed. The vessel is pressurized to the same pressure as the blast hose attached to the bottom of the pressure vessel. The abrasive is metered into the blast hose and conveyed by the compressed gas through the blast nozzle.
* Wet blast cabinets use a system that injects the abrasive/liquid slurry into a compressed gas stream. Wet blasting is typically used when the heat produced by friction in dry blasting would damage the part.
Blast room
A blast room is a much larger version of a blast cabinet. Blast operators work inside the room to roughen, smooth, or clean surfaces of an item depending on the needs of the finished product. Blast rooms and blast facilities come in many sizes, some of which are big enough to accommodate very large or uniquely shaped objects like rail cars, commercial and military vehicles, construction equipment, and aircraft.
Each application may require the use of many different pieces of equipment, however, there are several key components that can be found in a typical blast room:
* An enclosure or containment system, usually the room itself, designed to remain sealed to prevent blast media from escaping
* A blasting system; wheel blasting and air blasting systems are commonly used
* A blast pot – a pressurized container filled with abrasive blasting media
* A dust collection system which filters the air in the room and prevents particulate matter from escaping
* A material recycling or media reclamation system to collect abrasive blasting media so it can be used again; these can be automated mechanical or pneumatic systems installed in the floor of the blast room, or the blast media can be collected manually by sweeping or shoveling the material back into the blast pot
Additional equipment can be added for convenience and improved usability, such as overhead cranes for maneuvering the workpiece, wall-mounted units with multiple axes that allow the operator to reach all sides of the workpiece, and sound-dampening materials used to reduce noise levels.
Media
In the early 1900s, it was assumed that sharp-edged grains provided the best performance, but this was later shown to be incorrect.
Mineral:
Silica sand
Sand casting, also known as sand molded casting, is a metal casting process characterized by using sand as the mold material. The term "sand casting" can also refer to an object produced via the sand casting process. Sand castings are produced i ...
can be used as a type of mineral abrasive. It tends to break up quickly, creating large quantities of dust, exposing the operator to the potential development of
silicosis, a debilitating
lung disease
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side ...
. To counter this hazard, silica sand for blasting is often coated with resins to control the dust. Using silica as an abrasive is not allowed in
Germany
Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
,
Belgium
Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...
,
Russia
Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
,
Sweden
Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...
and
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
for this reason. Silica is a common abrasive in countries where it is not banned.
Another common mineral abrasive is
garnet
Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives.
All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different s ...
. Garnet is more expensive than silica sand, but if used correctly, will offer equivalent production rates while producing less dust and no safety hazards from ingesting the dust. Magnesium sulphate, or
kieserite
Kieserite, or magnesium sulfate monohydrate, is a hydrous magnesium sulfate mineral with formula (MgSO4·H2O).
It has a vitreous luster and it is colorless, grayish-white or yellowish. Its hardness is 3.5 and crystallizes in the monoclinic cry ...
, is often used as an alternative to
baking soda
Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3∠...
.
Agricultural: Typically, crushed nut shells or fruit kernels. These soft abrasives are used to avoid damaging the underlying material such when cleaning brick or stone, removing
graffiti
Graffiti (plural; singular ''graffiti'' or ''graffito'', the latter rarely used except in archeology) is art that is written, painted or drawn on a wall or other surface, usually without permission and within public view. Graffiti ranges from s ...
, or the removal of coatings from printed
circuit board
A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich struc ...
s being repaired.
Synthetic: This category includes
corn starch,
wheat starch
Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diet ...
,
sodium bicarbonate, and
dry ice
Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily ...
. These "soft" abrasives are also used to avoid damaging the underlying material such when cleaning brick or stone, removing graffiti, or the removal of coatings from printed circuit boards being repaired. Soda blasting uses baking soda (sodium bicarbonate) which is extremely
friable
Friability ( ), the condition of being friable, describes the tendency of a solid substance to break into smaller pieces under duress or contact, especially by rubbing. The opposite of friable is indurate.
Substances that are designated hazardous, ...
, the micro fragmentation on impact exploding away surface materials without damage to the substrate.
Additional synthetic abrasives include process byproducts (e.g.,
copper slag
Copper slag is a by-product of copper extraction by smelting. During smelting, impurities become slag which floats on the molten metal. Slag that is quenched in water produces angular granules which are disposed of as waste or utilized as discuss ...
,
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
slag
Slag is a by-product of smelting (pyrometallurgical) ores and used metals. Broadly, it can be classified as ferrous (by-products of processing iron and steel), ferroalloy (by-product of ferroalloy production) or non-ferrous/base metals (by-prod ...
, and
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when dea ...
slag), engineered abrasives (e.g.,
aluminium oxide,
silicon carbide
Silicon carbide (SiC), also known as carborundum (), is a hard chemical compound containing silicon and carbon. A semiconductor, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder and crystal s ...
or carborundum, glass beads, ceramic shot/grit), and recycled products (e.g., plastic abrasive, glass grit).
Metallic: Steel shot, steel grit, stainless steel shot, cut wire, copper shot, aluminium shot, zinc shot.
Many coarser media used in sandblasting often result in energy being given off as sparks or light on impact. The colours and size of the spark or glow varies significantly, with heavy bright orange sparks from steel shot blasting, to a faint blue glow (often invisible in
sunlight
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...
or brightly lit work areas) from garnet abrasive.
Safety
Cleaning operations using abrasive blasting can present risks for
workers' health and safety, specifically in portable air blasting or blast room (booth) applications. There is a large amount of dust created through abrasive blasting from the substrate and abrasive.
Although many abrasives used in blasting rooms are not hazardous in themselves, (steel shot and grit, cast iron,
aluminum oxide, garnet, plastic abrasive and glass bead), other abrasives (silica sand,
copper slag
Copper slag is a by-product of copper extraction by smelting. During smelting, impurities become slag which floats on the molten metal. Slag that is quenched in water produces angular granules which are disposed of as waste or utilized as discuss ...
, nickel slag, and
staurolite) have varying degrees of hazard (typically free silica or heavy metals). However, in all cases their use can present serious danger to operators, such as burns due to projections (with skin or eye
lesion
A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals.
Types
There is no designated classif ...
s), falls due to walking on round shot scattered on the ground, exposure to hazardous dusts, heat exhaustion, creation of an
explosive atmosphere, and exposure to excessive noise. Blasting rooms and portable blaster's equipment have been adapted to these dangers. Blasting lead-based paint can fill the air with lead particles which can be harmful to the nervous system.
In the US the
Occupational Safety and Health Administration
The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...
(OSHA) mandates engineered solutions to potential hazards, however silica sand continues to be allowed even though most commonly used blast helmets are not sufficiently effective at protecting the blast operator if ambient levels of dust exceed allowable limits. Adequate levels of respiratory protection for blast operations in the United States is approved by the
National Institute for Occupational Safety and Health
The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
(NIOSH).
Typical safety equipment for operators includes:
* Positive pressure blast hood or helmet – The hood or helmet includes a head suspension system to allow the device to move with the operator's head, a view window with replaceable lens or lens protection and an air-feed hose.
* Grade‑D air supply (or self-contained oil-less air pump) – The air feed hose is typically attached to a grade‑D pressurized air supply. Grade‑D air is mandated by OSHA to protect the worker from hazardous gases. It includes a pressure regulator, air filtration and a carbon monoxide monitor/alarm. An alternative method is a self-contained, oil-less air pump to feed pressurized air to the blast hood/helmet. An oil-less air pump does not require an air filter or carbon monoxide monitor/alarm, because the pressurized air is coming from a source that cannot generate
carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
.
* Hearing protection – ear muffs or ear plugs
* Body protection – Body protection varies by application but usually consists of gloves and overalls or a leather coat and chaps. Professionals would wear a cordura/canvas blast suit (unless blasting with steel abrasives, then they would use a leather suit).
In the past, when sandblasting was performed as an open-air job, the worker was exposed to risk of injury from the flying material and lung damage from inhaling the dust. The
silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
dust produced in the sandblasting process would cause silicosis after sustained
inhalation of the dust. In 1918, the first sandblasting enclosure was built, which protected the worker with a viewing screen, revolved around the workpiece, and used an exhaust fan to draw dust away from the worker's face. Silicosis is still a risk when the operator is not completely isolated from the sandblasting apparatus.
Sandblasting also may present secondary risks, such as falls from
scaffolding
Scaffolding, also called scaffold or staging, is a temporary structure used to support a work crew and materials to aid in the construction, maintenance and repair of buildings, bridges and all other man-made structures. Scaffolds are widely use ...
or confinement in a small space.
Carbon monoxide poisoning
Carbon monoxide poisoning typically occurs from breathing in carbon monoxide (CO) at excessive levels. Symptoms are often described as "flu-like" and commonly include headache, dizziness, weakness, vomiting, chest pain, and confusion. Large e ...
is another potential risk, from the use of small gasoline-powered engines in abrasive blasting.
Several countries and territories now regulate sandblasting such that it may only be performed in a controlled environment using ventilation, protective clothing and breathing air supply.
Worn-look jeans
Many consumers are willing to pay extra for
jeans that have the appearance of being used. To give the fabrics the right worn look sandblasting is used. Sandblasting has the risk of causing
silicosis to the workers, and in
Turkey
Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a list of transcontinental countries, transcontinental country located mainly on the Anatolia, Anatolian Peninsula in Western Asia, with ...
, more than 5,000 workers in the
textile industry
The textile industry is primarily concerned with the design, production and distribution of yarn, cloth and clothing. The raw material may be natural, or synthetic using products of the chemical industry.
Industry process
Cotton manufacturi ...
suffer from silicosis, and 46 people are known to have died from it. Silicosis was shown to be very common among former denim sandblasters in Turkey in 2007. A 2015 study confirmed that silicosis is almost inevitable among former sandblasters.
Sweden
Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...
's Fair Trade Center conducted a survey among 17 textile companies that showed very few were aware of the dangers caused by manually sandblasting jeans. Several companies said they would abolish this technique from their own production.
In 2013, research claimed that in China some factories producing worn-look jeans are involved in varied non-compliance with health and safety regulations.
Applications
The lettering and engraving on most modern
cemetery
A cemetery, burial ground, gravesite or graveyard is a place where the remains of dead people are buried or otherwise interred. The word ''cemetery'' (from Greek , "sleeping place") implies that the land is specifically designated as a buri ...
monuments and markers is created by abrasive blasting.
Sandblasting can also be used to produce three-dimensional signage. This type of signage is considered to be a higher-end product as compared to flat signs. These signs often incorporate gold leaf overlay and sometimes crushed glass backgrounds which is called
smalt
Cobalt glass—known as "smalt" when ground as a pigment—is a deep blue coloured glass prepared by including a cobalt compound, typically cobalt oxide or cobalt carbonate, in a glass melt. Cobalt is a very intense colouring agent and very litt ...
s. When sandblasting wood signage it allows the wood grains to show and the
growth rings
Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...
to be raised, and is a popular way to give a sign a traditional carved look. Sandblasting can also be done on clear
acrylic glass
Poly(methyl methacrylate) (PMMA) belongs to a group of materials called engineering plastics. It is a transparent thermoplastic. PMMA is also known as acrylic, acrylic glass, as well as by the trade names and brands Crylux, Plexiglas, Acrylite ...
and
glazing as part of a store front or
interior design
Interior design is the art and science of enhancing the interior of a building to achieve a healthier and more aesthetically pleasing environment for the people using the space. An interior designer is someone who plans, researches, coordina ...
.
Sandblasting can be used to refurbish buildings or create works of art (carved or
frosted glass
Frosted glass is produced by the sandblasting or acid etching of clear sheet glass. This creates a pitted surface on one side of the glass pane and has the effect of rendering the glass translucent by scattering the light which passes through ...
). Modern masks and resists facilitate this process, producing accurate results.
Sandblasting techniques are used for cleaning boat
hulls, as well as brick, stone, and concrete work. Sandblasting is used for cleaning industrial as well as commercial structures, but is rarely used for non-metallic workpieces.
See also
*
Abrasion (mechanical)
Abrasion is the process of scuffing, scratching, wearing down, marring, or rubbing away. It can be intentionally imposed in a controlled process using an abrasive. Abrasion can be an undesirable effect of exposure to normal use or exposure to t ...
*
Abrasive machining
Abrasive machining is a machining process where material is removed from a workpiece using a multitude of small abrasive particles. Common examples include grinding, honing, and polishing. Abrasive processes are usually expensive, but capable of ti ...
*
Air abrasion Air abrasion is a dental technique that uses compressed air to propel a thin stream of abrasive particles—often aluminum oxide or silica—through a specialized hand-piece to remove tooth tissue and decay before being suctioned away, similar to s ...
*
High-frequency impact treatment
The high-frequency impact treatment or HiFIT – Method is the treatment of welded steel constructions at the weld transition to increase the fatigue strength.
Features
The durability and life of dynamically loaded, welded steel structures is ...
*
Laser ablation, for laser blasting surface ablation instead of abrasive medium surface ablation
*
Shot peening
Shot peening is a cold working process used to produce a compressive residual stress layer and modify the mechanical properties of metals and composites. It entails striking a surface with shot (round metallic, glass, or ceramic particles) with ...
References
General and cited references
* ''Manufacturing Processes Reference Guide'', 1st ed., by Robert H. Todd, Dell K. Allen, and Leo Alting
* ''Tool and Manufacturing Engineers Handbook, Vol. 1: Machining'', 4th Edition, 1983. Society of Manufacturing Engineers
External links
*
{{Cleaning tools
Abrasive blasting
American inventions
Industrial processes
Cleaning methods