sand blasting

Sand blasting surface finishes 101: A Comprehensive Guide

Sand blasting surface finishes 101: A Comprehensive Guide

Sand Blasting is a process that uses sand to clean or remove paint, rust, or other unwanted substances from a surface. It can also be used to etch designs into glass or metal. The sand is accelerated by air pressure and hits the surface being cleaned at high speed. This leaves a smooth finish on the surface and removes any contaminants. This article will discuss all you need to know about sandblasting!

What is sandblasting?

Sandblasting is a process that uses high-pressure air to blast sand or other abrasive materials at the surface of a part. This process can be used to remove paint, rust, or other contaminants from a variety of surfaces. Sandblasting is also commonly used to prepare surfaces for painting or coating.

The sandblasting process can remove contaminants from the surface of a material, create a smooth or textured finish, and prepare the surface for painting or other treatments.

How does sandblasting work?

Sandblasting process is powered by air compressor, and the abrasive materials are mixed in a particular proportion and transported through pipes to the spray gun. When the abrasive materials and compressed air, pressure and injection Angle is appropriate, under the action of high-speed jet airflow, the workpiece’s surface will produce many fine particles.

The workpiece to be processed must be cleaned and degreased before sandblasting.

The choice of abrasive material depends on the type of surface to be processed, the required roughness and the degree of cleanliness.

Preparation work before sandblasting

  • ① Check the equipment. For example, nozzle, lighting, ventilation and compressed air are standard; whether the equipment leaks sand, if there is the above situation, it needs to be repaired before carrying out the work.
  • ② Count the number of parts if there is a lack of timely upward reaction to facilitate a timely search.
  • ③ Check the appearance of the parts. The sandblasting should be stopped if the parts have any defects such as hair-bumping, bumping, cracking, etc.
  • ④ Check whether the parts are all or locally sandblasted. If it is local sandblasted, The parts that do not require sandblasting should be sealed with protective wax or tape.
  • ⑤ Staff must wear protective equipment, such as masks, rubber gloves, work clothes, caps, etc.

The steps of the sandblasting process include:

Step 1:

Turn on the lighting, then open the compressed air valve, keep the nozzle working for 2~5 minutes first so that the water in the pipeline is sprayed away, so as not to make the sand wet, and then close the compressed air valve to insert the sand pipe into the sand.

The abrasives sand should be selected according to the finish requirements of parts, then put into the blasting equipment and adjusted to the required air pressure.

Step 2:

Put the parts into the sandblasting machine and close the machine door.

Protection measures should be taken in advance for parts that require no sandblasting.

Step 3:

Start the exhaust device, open the compressed air valve, and start sandblasting.

When sandblasting, the nozzle should be tilted 30° ~ 40°; Rotate or turn the part evenly and slowly move the part or nozzle back and forth so that the part’s surface is sprayed evenly until the surface of the part is all silver grey.

Step 4:

After sandblasting the parts, close the compressed air valve immediately and remove the parts. And check the surface cleanliness and roughness of the parts. Do not touch the parts with your hand directly.

4 main types of sandblasting

There are many different types of sandblasting, and each has its own unique set of benefits. The following are main types of sandblasting;

  • Wet blasting:

The main benefit of wet blasting is that it doesn’t create dust, making it ideal for use in enclosed spaces. it is also less likely to damage delicate surfaces than other types of sandblasting.

 

  • Dry blasting:

The main benefit of dry blasting is that it’s fast and effective at removing tough buildups. Dry blasting is also less likely to damage delicate surfaces than other types of sandblasting.

 

  • Soda blasting:

The main benefit of soda blasting is that it’s gentle enough to use on delicate surfaces without damaging them. it is also effective at removing tough buildups.

 

  • Abrasive blasting:

The main benefit of abrasive blasting is that it’s fast and effective at removing tough buildups. Abrasive blasting is also effective at removing paint and rust from surfaces.

5 Commonly used sandblasting materials:

  • Silicon carbide:

Silicon carbide is a complex, brittle, dark-grey or black mineral that occurs in nature as an intermediate product of silicon and carbon. Silicon carbide powder has been used since antiquity as an abrasive.

It belongs to the most expensive sandblasting materials, the consumption of the product is small, immediate effect, and the price is higher than the white corundum products.

 

  • White alundum:

The price is relatively high, but in removing some oxide layer to retain a particular unreactive workpiece, the product is the best choice; because of its higher purity, the price of white corundum products emery is also slightly higher.

 

  • Brown alumina

Brown alumina is a material made of aluminium oxide. It has a range of applications, including in the production of refractory bricks and as an abrasive.

This is one of the most cost-effective emery abrasive, sandblasting metals used in the wide range, and the fitness of the material is relatively high.

 

  • Quartz sand

Quartz sand is a type of sand made primarily of quartz. It is a prevalent type of sand found in many different places.

It is a kind of cheap sandblasting derusting material with low price, high hardness, extensive boiler maintenance, and large pipeline construction can be used with this material.

 

  • Black corundum:

Black corundum is a variety of the mineral corundum. It is the second hardest mineral on Earth, next to diamond. 

Black corundum is very rare and can be found in only a few places worldwide. Most of them are used in grinding wheel cutting, but very few are used in sandblasting.i

Surface Finish Grade of Sandblasting:

The surface roughness of the Sandblasting can be controlled by adjusting the nozzle, air pressure, abrasives type, size and distance between the nozzle and the surface.

Grade 0:

Clean to bare metal. No visible residue or staining is allowed. All oils, greases, oxides, corrosion products or other foreign matter must be completely removed.

Grade Sa:

Near White Metal Achieved by bead blasting with steel shot or grit, this finish is characterized by a clean, bright, metallic appearance free of staining or corrosion. The surface may have very fine streaks or lines that are generally not visible to the unaided eye. This is an ideal finish for many decorative applications.

Grade Sb:

White Metal Achieved by bead blasting with steel shot or grit, this finish is similar to Sa but may have slightly more visible lines or streaks. This finish is also well suited for decorative applications.

Grade Sc:

Commercial A bright, clean metal surface free of most foreign matter produces this finish by bead blasting with steel shot or grit. It may have a slightly pebbled appearance and is commonly used for architectural applications.

Grade Sd:

Brushed Achieved by bead blasting with steel shot or grit, this finish has directional lines running the length of the sheet. It is commonly used for decorative purposes.

Grade Se:

Matte bead blasted finish with a dull, non-reflective surface. This finish is commonly used for industrial applications where a decorative finish is not required.

Advantages of sandblasting

Rust Removal

Sandblasting can remove all dirt, oxide layer and rust on the surface of the workpiece and establish a very important finish on the surface of the workpiece.

Improved adhesion

It can be replaced with different particle size abrasive, achieve different degrees of roughness, and significantly improve the workpiece, coating, and plating force. Or make the bonding parts stick more firmly better quality.

Decorative effect

Abrasive blasting cleaning can make the workpiece show uniform metal colour, make the appearance of the workpiece more beautiful, and beautify the role of decoration.

Improve mechanical properties

Mechanical parts, after abrasive blasting, it can produce a uniform fine concave and convex surface on the surface of the parts, and improve the fatigue strength, wear resistance and corrosion resistance of parts.

Stress relief

By hitting the surface of the workpiece with sand balls, the stress is eliminated, and the surface strength of the workpiece is increased, such as the surface treatment of spring, machining tool and aircraft blade.

Application of sandblasting

Sandblasting process is widely used in ships, automobiles, bridges, machinery, pipelines and other industries. The specific applications are as follows:

  • Remove paint or rust from ships, vehicles, bridges or other metal surfaces.
  • Clean the surface of the workpiece before electroplating or applying a coating.
  • Prepare the surface of the workpiece for bonding.
  • Remove oxides or other foreign matter from the surface of glass, ceramic or metal products.
  • Produce a uniform, matte finish on metals, glass or stone.
  • Clean moulds and dies.
  • Prepare surfaces for painting or other finishes.

Bead blasting VS Sandblasting, What is the difference?

Why choose bead blasting?

Bead blasting is a process that uses small beads of glass or ceramic to remove surface material. The bead blasting process is typically used to clean metal parts or to prepare them for painting. Bead blasting can also be used to create a matte finish on metal surfaces.

After bead blasting treatment, the surface dirt of the workpiece is removed, the surface of the workpiece is not easy to be destroyed, and the surface area is increased. Because the workpiece surface is not damaged during the machining process, the excess energy generated during the machining will cause the surface strengthening of the workpiece matrix.

Why choose Sandblasting?

Sandblasting, on the other hand, uses sand particles to remove surface material. Sandblasting is typically used to remove paint or rust from metal surfaces. It can also be used to create a textured finish on metal surfaces.

After sandblasting treatment, the surface dirt of the workpiece is removed, the surface of the workpiece is damaged slightly, and the surface area is greatly increased, thus increasing the binding strength of the workpiece and the coating/coating.

The workpiece surface of sandblasted for natural metal colour, but because of the rough surface, and light refraction, there is no metal lustre for the dark surface.

Bead blasting produces a clean, smooth finish, while sandblasting produces a textured finish.

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