The Basis of Sandblasting
Sandblasting, also known as abrasive blasting, is a surface treatment process that forces solid abrasive particles onto a surface through compressed air. The abrasive particles remove rust, paint, contaminants or roughen the surface as desired. Sand, glass beads, plastic pellets or metal shot can be used as abrasives.
Purposes of Sandblasting
Sandblasting is used for a variety of purposes across many industries. Some of the main uses and goals of sandblasting include:
- Removing Contaminants – Sandblasting can remove dirt, rust, scale, paint or other unwanted layers from the surface of materials like metal, concrete, stone or fiberglass. The high-velocity abrasive particles break the bonds between the contaminants and the substrate.
- Finishing and Smoothing – After blasting off any coatings or oxidation, the exposed bare substrate can then be smoothed and polished through sandblasting. This gives metal, glass, stone, etc. a uniform matte finish or shine.
- Etching and Carving – Sandblasting slowly cuts away material so it can be used to etch designs, lettering, textures or other desired patterns into glass, stone, metal and hard plastics. The abrasive wears away the surface unevenly to create carved grooves and recesses.
- Prepping Surfaces – Sandblasting prepares surfaces like metal or concrete for painting or powder coating by roughing up the substrate to help coatings better adhere. A roughened, textured surface gives paint something to grip.
- Cleaning Mold and Tooling – Gentle sandblasting cleans dirt, debris and buildup off of manufacturing and industrial equipment like injection molds, press tooling and jigs. It restores the mold’s as-new condition.
- Removing Corrosion – Rust, oxidation and corrosion can be quickly stripped from metal surfaces through abrasive blasting rather than manual scrubbing or chemical baths. This restores the bare substrate.
Types of Sandblasting
There are several variations of the sandblasting process that use different equipment setups and abrasive media to suit different applications:
- Dry Sandblasting – The traditional method where compressed air blows abrasive powder or grains directly at the surface. It creates dust that requires containment.
- Wet Sandblasting – A stream of water is added to the abrasive blast. This suppresses dust while using the water’s mass to increase cutting speed.
- Vacuum Sandblasting – A vacuum hood or enclosure surrounds the blasting nozzle to safely collect used abrasive media and dust for disposal. This contains debris.
- Micro Sandblasting – Finer abrasive particles moving at lower speeds allow for controlled, delicate surface etching or finishing of intricate parts.
- Bead Blasting – Small glass or plastic beads are used as smoother, more rounded abrasives for polishing or finishing sensitive surfaces.
- Soda Blasting – Baking soda particles dissolve upon impact, making this a gentle option for cleaning delicate surfaces. Rinses away easily.
- Steel Shot/Grit Blasting – More angular steel particles provide aggressive cutting action for removing thick coatings or heavy corrosion.
- Sandblasting Robots – Programmable robotic arms automate blasting for high throughput, consistency and safety. They can scan and match to CAD models.
Materials Suitable for Sandblasting
- Air Compressor – Provides a high pressure stream of air to accelerate the abrasive media. Air pressure can range from 10 psi for delicate work up to 150 psi for aggressive material removal.
- Blast Pot – A chamber that stores and mixes the abrasive media with the compressed air stream. It includes controls to regulate media flow.
- Blast Nozzle – The nozzle shapes and directs the abrasive stream at the work surface. Nozzle size, shape and material affect the blast pattern.
- Hoses and Couplings – Durable, thick hoses convey the air-abrasive mixture from the pot to the blasting nozzle.
- Media – Substances used as abrasive particles for sandblasting include:
- Sand – Silica sand is a common, inexpensive medium but creates fine dust.
- Mineral Slags – Byproducts like coal or copper slag are reused as sharp, low-dust abrasives.
- Steel Shot/Grit – Angular steel particles cut aggressively for coating and rust removal.
- Glass Bead – Rounded glass beads are softer for polishing and finishing work.
- Walnut Shells – Organic crushed walnut shells are used for delicate cleaning.
- Aluminum Oxide – Hard, sharp abrasive for etching and cleaning hard materials.
- Bake Soda – Dissolvable, non-toxic particles for delicate cleaning.
The right media, equipment and settings can be tested to match the particular sandblasting application. Proper protective gear for the operator is also crucial.
The Sandblasting Process
Performing sandblasting involves these key steps:
- Surface Prep – The surface to be blasted must be clean and dry. Masking tape or peelable rubber masking agents are applied to protect areas not to be blasted.
- Selecting Abrasive Medium – Consider the goal of blasting along with the surface material when selecting the right abrasive medium and mesh size.
- Operating the Blaster – The object to be blasted is placed inside the blast cabinet or a blast operator wears protective gear. The abrasive blast nozzle is directed at the surface at optimal distance and angle.
- Monitoring Progress – As blasting proceeds, the surface is checked periodically to inspect progress and ensure even treatment. The abrasive flow rate, nozzle distance and blast pattern may need adjustment.
- Stopping and Checking – When the desired effect is achieved, blasting is stopped. The surface is thoroughly cleaned to remove any debris or remnants of abrasive media.
- Secondary Processing – After blasting, secondary steps like smoothing, polishing, coating, etc. may be required depending on the goal.
- Cleanup and Maintenance – The blast equipment and cabinet are cleaned out and checked for wear. Used abrasive media is properly disposed of.
With the right setup and technique, sandblasting can quickly alter the surface properties of materials. Always test on samples first to dial in the proper treatment.
Industrial Applications of Sandblasting
Sandblasting is utilized across many industries for its ability to clean, finish, etch or alter surfaces:
- Automotive – Sandblasting removes unwanted paint, rust or oxidation from auto bodies prior to recoating. It also cleans cast engine parts.
- Aerospace – Aircraft and jet components are sandblasted to achieve the proper surface finish or to strip old coatings. It is also used for engine part maintenance.
- Maritime – Sandblasting removes barnacles and corrosion from boat hulls, decks and other marine hardware. It prepares surfaces for new protective coatings.
- Construction – Sandblasting etches and carves stone or concrete for decorative architectural purposes. It’s also commonly used for graffiti removal and to prep surfaces for painting.
- Manufacturing – Sandblasting cleans and refurbishes manufacturing equipment like molds, jigs, dies and tooling. It removes scale, oxidation and surface defects from cast or machined parts.
- Oil and Gas – Sandblasting cleans and maintains drilling equipment. It is also used for removing scales or coatings from pipes and valves.
- Monuments and Statues – Gentle sandblasting cleans built-up dirt, pollution and corrosion from stone monuments and metal statues while preserving the integrity of the substrate.
The list of applications across industries is extensive. Sandblasting is valued for its versatility and ability to quickly alter surface properties.
Sandblasting in Jewelry and Accessories
Sandblasting is commonly used in jewelry-making and accessories for finishing metals and etching designs:
- Preparing Metals – Jewelry metals like gold, silver, platinum, titanium and stainless steel are first sandblasted to create a matte finish that better highlights stamped patterns, textures and set gemstones.
- Etching – Light sandblasting can etch decorative patterns, logos, text and digitized designs onto metal jewelry pieces, watch cases, glasses frames, belt buckles and more.
- Stone Setting – The rough surface left by sandblasting provides added grip and an indentation for gemstones to be securely set on rings, pendants, cufflinks, etc.
- Distressing – Sandblasting metal with a random pattern creates a distressed or antiqued finish on items like watch bands, bracelets, decorative buckles and eyeglass frames.
- Surface Cleanup – Gentle blasting can remove tarnish, residue or oxidation from jewelry and accessories without damaging softer precious metals and stones.
- Reconditioning – Light sandblasting refurbishes and cleans jewelry pieces to revive them and give vintage or heirloom jewelry a refreshed look.
In many fashion jewelry designs, the sandblasted texture offers a unique look and feel. Some examples include:
- Rings, pendants, bracelets where sandblasting creates a rough, matte texture as a contrast to smooth surfaces.
- Necklaces, bangles where sandblasting enables etching decorative patterns like tattoos, animal prints, etc.
- Watch cases, eyeglass frames where fine sandblasting removes shine for a raw, natural aesthetic.
- Belt buckles, bag clasps where sandblasting adds visual interest and texture.
The sandblasted surface often serves as the final product without polishing or finishing required. But blast intensity needs to be controlled to avoid damaging the jewelry.
Comparison to Polishing, Brushing and Grinding
- Polishing (Click to learn more) – Polishing uses abrasive polishing compounds and soft cloths or pads to remove surface defects and make the material smooth and shiny. It makes surfaces smoother while sandblasting roughens them.
- Brushing (Click to learn more) – Brushing utilizes abrasive sticks or wheel brushes along with cutting fluid to remove deformation and surface flaws. It also aims to make surfaces smoother, unlike sandblasting.
- Grinding (Click to learn more) – Grinding uses coarse abrasive wheels to aggressively remove material and smooth surfaces. Like polishing and brushing, it creates smoothness whereas sandblasting does the opposite.
In summary, polishing, brushing and grinding aim to create very smooth flaw-free surfaces. In contrast, sandblasting roughens surfaces by blasting abrasive media at high velocities. This allows specific textures or patterns to be produced.