Before painting steel components, shot blasting removes rust and prepares the surface. Control surface cleanliness, roughness, and operating parameters. The process covers pre-blasting treatment, equipment selection, blasting, post-treatment, and precautions.
Surface requirements before blasting
Steel components must meet these conditions:
No oil or moisture. Oil prevents shot from contacting the metal base. Moisture can cause rust rebound.
No rust or oxides. Remove oxide scale and loose rust completely to avoid under-coating corrosion.
No sticky contaminants. Remove weld spatter, dust, and similar debris with compressed air blow-off.
No acid or alkali residue. After chemical cleaning, neutralize and rinse thoroughly.
After blasting, form an anchor profile depth of 40 to 70 μm to improve coating adhesion.
Shot blasting equipment selection and operation points
Equipment types:
Pneumatic automatic recovery shot blasting equipment: compressed air drives shot, with an automatic recovery system. Suits large-area continuous work.
Screw or scraper conveyor plus bucket elevator recovery shot blasting equipment: mechanical shot conveying. Suits high capacity and reduces manual work.
Small cabinet shot blasting machine: portable, suits local repair or small components.
We can machine custom nozzles, wear liners, fixtures, and other precision parts for shot blasting equipment from customer drawings, for single-piece or low-volume production.
Abrasive selection:
Steel grit and steel shot suit high-strength steel components. They give strong impact and do not break easily.
Quartz sand costs less but produces much dust. It needs a dust collection system.
Copper slag has moderate hardness and suits soft metals such as aluminum alloy.
Operating parameters:
Compressed air pressure is usually 0.5 to 0.7 MPa. Too high deforms the workpiece. Too low reduces cleaning efficiency.
Blasting distance is 150 to 300 mm. Too close damages the substrate. Too far disperses the shot.
Blasting angle perpendicular to the workpiece surface gives the best cleaning. Keep the tilt angle at 75° to 90°.
Shot blasting process
Pretreatment: Remove weld spatter, burrs, and other sharp impurities to avoid scratching the workpiece. For galvanized layers, use light sweep blasting to remove the oxide layer while keeping the zinc layer's corrosion protection.
Blasting: Work in zones. Divide work areas by component structure to avoid missed or repeated blasting. Cover evenly. Move the shot in a spiral path to cover all surfaces, including edges and internal cavities. Check in real time. After every 1 m², compare roughness with a standard sample. Re-blast any area that fails.
Post-treatment: Blow off residual shot with compressed air. Reach Sa2.5 (Swedish standard) or SSPC-SP10 (US standard). Apply the first primer coat within 4 hours after blasting to prevent rust return. For welded parts, wait 72 hours after welding before coating.
Features of environmental shot blasting equipment
An integral sand suction floor recovers 100% of shot. No residual abrasive on site, reducing dust emissions.
Dust concentration is below 8 mg/m³, meeting national environmental standards.
No deep pit foundation is needed, saving over 30% in civil construction costs.
Low failure rate, maintenance cost reduced by 50%, downtime shortened to within one hour.
It can use steel grit, steel shot, quartz sand, and other abrasives, with fast process switching.
Sufficient indoor lighting and good visibility improve the operating environment.
Precautions
Safety protection: Operators wear dust masks, safety goggles, and noise-reducing earplugs. Emergency stop buttons are installed in the blasting room.
Abrasive management: Regularly test abrasive particle size distribution. Replace when wear rate exceeds 30%.
Equipment maintenance: Clean dust collector filter elements daily. Check screw conveyor wear weekly.
Proper operation of shot blasting equipment brings steel component surfaces to the required cleanliness and roughness for coating. This improves coating adhesion and corrosion resistance and extends component service life.
Our custom precision component machining capability is not limited to shot blasting equipment. Beyond nozzles, wear liners, and fixtures for shot blasting equipment, we also machine yacht precision components, RC car structural parts, medical device parts, and non-standard parts for food machinery and textile machinery. Hansheng Automation works from customer drawings and production quantities to deliver single-piece or low-volume precision machining.
