Sandblasting (also called abrasive blasting) is the process of propelling abrasive particles at high velocity against a surface to clean, roughen, or polish it. It covers a broad family of techniques differentiated by abrasive media: sand blasting (silica sand — increasingly restricted for health reasons), steel shot blasting (for heavy cleaning/peening), glass bead blasting (for bright satin finish), aluminum oxide blasting (for etching/roughening), soda blasting (gentle cleaning of soft surfaces), and dry ice blasting (non-abrasive cleaning for delicate equipment).
The process is widely used in China for surface preparation before painting/coating, rust and scale removal from steel structures, cosmetic finishing of die-cast and machined parts, and shot peening for fatigue life improvement. Many overseas buyers underestimate the impact of blasting parameters (pressure, nozzle distance, media type) on the final surface appearance — what looks like a simple "same surface" actually varies dramatically between shops.
| Abrasive Type | Particle Size (Mesh) | Hardness (Mohs) | Air Pressure | Surface Profile (Ra) | Best For |
|---|---|---|---|---|---|
| Silica sand | 16–60 mesh | 7 | 4–7 bar | 3.0–12.5 μm | Heavy rust/scale removal (restricted in many countries) |
| Steel grit | G14–G80 (0.2–1.5 mm) | 6–7 | 5–8 bar | 5.0–25 μm | Shot peening, heavy cleaning of castings/forgings |
| Aluminum oxide | 24–320 mesh | 9 | 3–7 bar | 1.5–8.0 μm | Precision etching, surface preparation for bonding/coating |
| Glass beads | 40–325 mesh | 5–6 | 2–5 bar | 0.8–3.0 μm | Bright satin finish, deburring thin parts |
| Plastic media | 12–60 mesh | 3–4 | 1.5–4 bar | 1.0–4.0 μm | Stripping coatings, cleaning soft metals |
| Walnut shell | 16–40 mesh | 2–3 | 1–3 bar | 0.5–2.0 μm | Gentle cleaning, wood/fiberglass restoration |
| Baking soda | 50–200 mesh | 2.5 | 2–5 bar | 0.5–1.5 μm | Cleaning without etching substrate, no residue |
China's casting and heavy steel structure hub — hundreds of shot blasting/sandblasting lines serving foundries. Most have tumble-blast machines for small castings and cabinet-blast lines for structural steel. Shot blasting prices: ¥200–500/ton ($30–75/ton) for large volumes. Silica sand blasting is still common despite regulations (often in open-air yards). Good for industrial-scale surface prep but not fine decorative finishing.
Precision sandblasting hub for consumer electronics, die-cast zinc/aluminum parts, and architectural hardware. Hundreds of small shops with automated blasting cabinets using glass beads, aluminum oxide, or ceramic beads. Capable of consistent satin matte finishes on aluminum and stainless steel. Prices: ¥2–15/piece for small parts ($0.30–2.20/piece). Custom masking for selective blasting is available (expensive but well-executed).
Foundry and automotive component region with integrated shot blasting lines. Many IATF 16949-certified factories with robotic shot blasting for engine blocks, transmission housings, and suspension components. Wheel shot blasting (for automotive wheel pre-treatment before powder coating) is a specialty. Prices: ¥300–800/ton ($45–120/ton). Consistent quality due to process automation.
Health and safety red flag: Silica sand blasting is still widely practiced in Chinese open-air or poorly ventilated workshops. Inhaled crystalline silica dust causes silicosis — a fatal lung disease. China has regulations (GBZ 2.1-2019 limit: 0.7 mg/m³ respirable crystalline silica) but enforcement is inconsistent. For your protection and to avoid supply chain liabilities, always specify "silica-free abrasive blasting" (use aluminum oxide, glass beads, garnet, or steel grit instead). This costs 20–50% more but eliminates the health and regulatory risk. Many European and US importers now require this in their supplier contracts.
Too much blasting pressure or time can erode material from the surface, change dimensional tolerances (especially on threaded holes and fine features), and work-harden thin sections. For aluminum die-cast parts, over-blasting can erode through thin walls (0.8–1.2 mm) — we've seen this causing 10% rejection rates on electronic enclosures. Key rule: for thin-walled parts (< 2 mm), use glass beads at low pressure (2–3 bar) and keep nozzle distance at least 200 mm.
After blasting, abrasive particles can become embedded in the surface — especially in softer metals (aluminum, brass, zinc). This embedded media can cause: (1) paint/coating adhesion failure, (2) corrosion spots from trapped moisture around particles, and (3) cosmetic defects after anodizing or plating. Mitigation: specify "compressed air blow-off + ultrasonic cleaning" after sandblasting. For critical surfaces, test with a white cloth wipe and 10× magnification inspection.
When only certain areas of a part should be blasted (e.g., satin finish on external surfaces with as-machined internal cavities), the masking must be precise and durable enough to withstand the abrasive impact. Standard vinyl tape fails within 10–20 seconds of blasting. Better options: silicone rubber masking, polyurethane tape, or custom machined aluminum masks. Budget significant cost for complex masking — it can add 50–100% to the blasting cost.
| Process | Cost per m² | Notes |
|---|---|---|
| Sand blasting (open air, silica sand) | ¥10–30 ($1.50–4.50) | Cheapest but increasingly restricted. Good for heavy rust removal |
| Sho blasting (steel shot, cabinet) | ¥15–50 ($2.25–7.50) | Recoverable media (reused 100×+). For casting/forging cleaning |
| Glass bead blasting (cabinet) | ¥20–60 ($3.00–9.00) | Premium for fine satin finish. Media is single-use or reclaimed |
| Aluminum oxide blasting (cabinet) | ¥30–80 ($4.50–12.00) | Most expensive. For precision etching and critical surface preparation |
| Dry ice blasting | ¥80–200 ($12.00–30.00) | No abrasive residue. Used for in-place cleaning of equipment |
| Special: selective masked blasting | ¥50–150 ($7.50–22.00)+ per m² | Custom masking + handling adds significant cost |
Minimum charge: ¥100–300 ($15–45) for cabinet work. For high-volume production (1,000+ parts/month), per-piece pricing drops 30–50%. Shot blasting costs are typically ¥200–800/ton for heavy castings/structural work.
Sandblasting is a surface cleaning/preparation process — the goal is to remove contaminants, old coatings, and create a surface profile. Shot peening is a cold working process — small spherical shot (steel, glass, ceramic) is blasted at the surface with sufficient kinetic energy to create compressive residual stresses, improving fatigue life of the part. The key differences: shot peening uses specifically sized spherical media, controlled coverage (98–200% by Almen strip measurement), and aims for surface compression rather than material removal. Do not confuse them in your specification — they solve very different problems.
Yes, typically by 0.003–0.050 mm per surface depending on media hardness, pressure, and blasting duration. For most applications this is negligible. For precision parts with tolerances < 0.05 mm, account for this material removal in your dimension stack. Mask critical surfaces (ground sealing faces, threaded holes, bearing seats) before blasting. Thin blow-molded or extruded walls (< 1.0 mm) are especially vulnerable to dimensional change.
Don't just say "matte finish" — it's too vague. Specify: "Glass bead blasting using 100–200 mesh glass beads at 3–4 bar pressure, nozzle distance 150–250 mm, achieving uniform satin surface with Ra 1.5–3.0 μm, no visible directional patterns." If you have a physical sample or a RAL/ISO reference plate, send it. Chinese shops understand "matt 哑光" or "细砂面" (fine sand surface) but this still leaves much to interpretation — the most reliable method is to approve a first sample and keep it as a reference.
Yes — in fact, sandblasting is excellent for weld prep because it removes mill scale, rust, and oil simultaneously. But caution: if silica sand is used and particles remain embedded in the surface, silica can contaminate the weld pool and cause inclusions or porosity. For weld prep, specify "aluminum oxide or garnet blasting" and ensure the surface is brushed or blown clean before welding. Alternatively, use steel shot — the embedded particles won't contaminate steel welds.
Yes — especially silica sand blasting. Inhaled crystalline silica dust survives in lung tissue and causes silicosis, a progressive and incurable lung disease. China recorded over 8,000 new occupational silicosis cases in 2023. For your supply chain, always require: (1) silica-free abrasive, (2) blast cabinet with dust collection (HEPA filtration), (3) operator personal protective equipment (PPE) including supplied-air respirator. For the environment: blast media waste is typically classified as hazardous if contaminated with heavy metals from the surface being cleaned, and must be disposed of properly.