Different purposes
Shot blasting is generally selected for heavier cleaning, rust/scale removal and profile creation before coating. Glass bead blasting is selected for cleaning and satin finishing where a less aggressive, more appearance-sensitive process is required.
The correct route depends on material, contamination level, next process and final appearance expectation.
Surface profile and coating adhesion
Coatings often need a profile to adhere properly. Shot blasting can create stronger mechanical anchor patterns, but excessive profile can affect thin coatings, threads and precision dimensions.
Glass bead blasting creates a smoother satin finish and may be better where the final look matters or where stainless cleanliness is important.
Stainless steel contamination
For stainless steel, carbon-steel contamination is a major concern. Steel shot or contaminated media can embed iron particles that later rust. Glass bead blasting with clean media is often preferred for stainless appearance and pre-passivation preparation.
The blasting area and media must remain clean. A stainless job processed with contaminated media can fail despite using a corrosion-resistant base material.
Approval through sample
Blasting results depend on incoming surface, media size, air pressure, distance, angle and coverage. A written description such as “matte finish” may not be enough.
Appearance-sensitive customers should approve a sample or reference finish before bulk work.
Process comparison
| Factor | Shot blasting | Glass bead blasting |
|---|---|---|
| Cleaning intensity | Higher; good for rust/scale/profile. | Lower; good for satin cleaning and appearance. |
| Surface profile | More pronounced. | Smoother satin texture. |
| Stainless suitability | Only with correct media control; contamination risk exists. | Commonly preferred where clean satin stainless finish is needed. |
| Before coating | Useful for adhesion profile. | Useful where lighter profile or cosmetic finish is needed. |
Practical conclusion
Shot blasting and glass bead blasting should not be treated as interchangeable. One is profile-heavy preparation; the other is cleaner, finer finishing when properly controlled.
How buyers should use this guide in an RFQ
For a technically complete coating RFQ, the customer should provide the drawing, material, quantity, current surface condition, required coating system, thickness or coating-mass expectation, salt spray target, masking requirement and packaging expectation. For zinc flake, Xylan/PTFE and phosphating work, route selection cannot be separated from geometry, surface preparation and post-coating handling.
If the part has threads, internal drives, blind holes, seal faces, bores or close-tolerance assembly zones, those areas should be marked before sampling. Coating build-up, retained coating, masking witness marks and post-curing handling must be accepted or corrected during sample approval rather than after bulk production.
Common avoidable rejection causes
- Approving corrosion performance without checking actual assembly, torque, thread fitment or bore clearance.
- Using ordinary cardboard or recycled paper directly against zinc-based coatings during humid storage.
- Bulk-packing Xylan/PTFE or zinc flake parts so that sharp edges and threads abrade the coating during transport.
- Leaving freshly blasted steel exposed before coating, causing flash rust or surface contamination.
- Treating salt spray hours as a universal field-life guarantee without considering storage, handling and exposure conditions.
Documentation and approval discipline
For controlled coating work, approval should include coating route, surface preparation method, number of coats, curing condition, measurement method, visual standard and packaging method. If the customer later changes part geometry, incoming condition, dispatch packing, storage duration or fitment requirement, the approved coating route should be revalidated before production continuation.