Sandblasting is a critical surface pretreatment process for aluminum die casting parts. It removes oxide layers, flash, oil, and other surface impurities left over from the casting procedure, while creating a fine texture on the surface that greatly improves the adhesion of spray painting, powder coating, or anodizing. Sandblasting can also expose hidden casting defects such as pores or cracks, which helps to achieve quality control more effectively.
This article will systematically explain the sandblasting media, standard operating procedures, required equipment, and key benefits for aluminium die casting components. Read on to learn how to achieve the ideal sandblasted surface effect for aluminium alloy die casting parts.
Sandblasting Media for Aluminum Die Castings
Glass Beads
Glass beads are often used for die casting products that require a clean, matte surface without changing the parts’ dimensions.
The smooth spherical particles can gently clean the surface without damaging detailed structures, especially for appearance parts, or parts that need to be anodized or sprayed.
Plastic Pellets
Plastic particles can remove coatings, powders, or contaminants without damaging the substrate.
Ideal for thin-walled or precision metal die casting components, with low heat generation and effectively avoids thermal deformation.
Walnut Shells
Walnut shells are environmentally friendly blasting media suitable for cleaning complex die casting parts.
It is gentle enough to protect casting details while effectively removing light oxide layers or residues, and is often used for castings with high surface sensitivity requirements.
Baking Soda (Sodium Bicarbonate)
Baking soda is a non-destructive blasting material that can remove oils and oxides without changing the dimension and leaving no residue, making it ideal for surface pretreatment before chemical treatments such as anodizing.
Aluminum Oxide
Aluminum oxide is used when a stronger surface roughness is required to enhance coating adhesion.
It can form a rough texture and improve mechanical bonding, but the intensity of use must be strictly controlled, otherwise, it may damage the surface or edges of the part.
Unrecommended Blasting Media
Hard blasting materials such as steel grit or silicon carbide are not suitable for aluminium alloy die casting.
Due to they will cause surface pits, embed metal contaminants, or deform thin-walled castings.
Sandblasting Operation Process
Pre-Cleaning
Before sandblasting, contaminants such as oil, dust, coolant, or release agent on the surface of the die casting aluminum should be removed to ensure that the sandblasting media can evenly contact the surface and form a consistent treatment effect.
Media Selection
Sandblasting media should be selected according to the product surface requirements, structural shape, and subsequent treatment process.
For example, the part to be powder-sprayed may require a rougher surface, while anodizing requires a finer surface texture.
Equipment Settings
The air pressure, nozzle size, spray distance, and angle need to be adjusted correctly. For aluminium die casting components, 30-60 PSI pressure is recommended.
Improper parameter settings may cause uneven surface, excessive wear, and even deformation of thin-walled structures.
Sandblasting Skills
Sandblasting operations should maintain uniform and continuous movement to avoid overspraying in a certain area.
Grooves or small ribs need to be precisely controlled to ensure comprehensive treatment and avoid omissions or excessive wear.
Post-Sandblasting Inspection
After sandblasting, the die casting products’ surface uniformity, defects, and suitability for the next process need to be inspected.
This includes observing pores, cracks, discoloration, and residual blasting media, so timely repairs can be made to avoid waste in later processing.
Subsequent Processing
After sandblasting, the parts should be sprayed, anodized, or polished as soon as possible.
Die casting aluminum is easy to reoxidation rapidly after sandblasting, which will affect the adhesion of the coating, so the subsequent processes need to be carried out in time to stabilize the surface state.
Die Casting Blank & Sandblasted Die Casting Part
Sandblasting Equipment
Sandblasting Cabinet/Sandblasting Room
The closed sandblasting space can effectively control dust, prevent pollution, and ensure the consistency of processing parameters.
It is recommended to use a sandblasting cabinet for small parts and a sandblasting room for large batches or large parts.
Air Compressor
Generating high-pressure airflow and driving the abrasive media towards the surface of aluminum die casting components.
The air compressor can provide a stable and continuous supply of clean and dry compressed air to ensure consistent sandblasting force and surface quality of castings.
Nozzle System
It is recommended to use ceramic or boron carbide nozzles, which are wear-resistant and have high sandblasting accuracy.
For fine aluminium alloy die casting parts, small nozzles can be used to accurately control the spray range to prevent accidental damage to areas that do not need to be treated.
Dust Removal System
Dust must be effectively controlled during sandblasting to protect operators and avoid secondary contamination of products.
The dust removal system helps improve visibility, recycle sandblasting media, and meet environmental requirements.
Advantages of Sandblasting on Aluminum Die Castings
Consistent Surface Quality
Sandblasting can remove flash, mold residues, and oxide layers, making die casting parts present a clean and uniform matte effect, improving product vision and texture.
Enhance Coating Adhesion
By forming a micro-concave and convex structure, sandblasting can greatly improve the adhesion of powder coating, spray painting, or anodizing, and extend the life of automotive die casting components in harsh environments.
Improve Heat Dissipation Performance
For thermal management components such as heat sinks, sandblasted surfaces increase the effective contact area, which is conducive to air flow and heat exchange, and is suitable for fields such as electronics, lighting, and new energy.
Improve Mechanical Strength
Sandblasting can introduce micro-compressive stress on the surface, reduce crack propagation, and improve fatigue resistance.
It is suitable for structural casting parts that are loaded or vibrate frequently.
Helps with Quality Inspection
Sandblasting can clearly expose casting defects such as pores, inclusions, or shrinkage marks, making it easier to screen out defective products before subsequent processing and improve the yield rate.
Conclusion
Sandblasting plays a key role in improving the functionality and appearance quality of aluminium alloy die castings.
It improves coating adhesion, reveals casting defects, enhances heat dissipation and mechanical properties, and achieves a clean and uniform surface effect.
As a leading aluminum die casting company, CEX Casting seamlessly integrates sandblasting into our entire die casting process.
Contact us today to get the customized surface treatment solutions for your next die casting project.