Vibrofinishing of metals


Vibrofinishing of metals is a surface finishing process used to improve the aesthetic appearance and functional properties of metal parts. This method is particularly effective for removing burrs, polishing, smoothing and cleaning metal surfaces.

Vibrofinishing process

Loading Material: The metal pieces to be treated are loaded into a vibrating machine together with abrasive media (also called "chips" or "finishing media") and specific chemical compounds.

Mechanical action: The vibrating machine, usually a circular or rectangular tub, vibrates at a high frequency. This motion causes friction between the metal pieces and the abrasive media, removing excess surface material and improving the finish.

Use of abrasive media: Abrasive media can be of different materials and shapes, including ceramic, plastic, steel or natural compounds such as coconut. The choice of media depends on the type of metal to be treated and the desired level of finish.

Chemical compounds: During the process, chemical compounds are added that help lubricate, clean and protect metal surfaces. These compounds can include detergents, corrosion inhibitors and polishing agents.

Abrasive media

Abrasive media play a crucial role in vibrofinishing, determining the quality and speed of the finishing process. Let's look at the most commonly used types of abrasive media and their specific details:

Ceramic media:

Materials: Aluminum oxide, aluminum silicate, zirconium.

Properties: High density and hardness, ideal for material removal and rough sanding.

Shapes: Cones, cylinders, triangles.

Applications: Used for hard steels, heavy alloys and parts requiring high material removal.

Ceramic media
Ceramic media

Plastic media:

Materials: Polymeric resins, often filled with abrasives such as silicon carbide.

Properties: Less aggressive than ceramic media, suitable for delicate finishing and polishing.

Shapes: Pyramids, cylinders, stars.

Applications: Ideal for soft metals such as aluminium, brass and zinc alloys.

Stainless steel media:

Materials: Stainless steel spheres or cylinders.

Properties: High density and corrosion resistance, excellent for polishing and tumbling.

Shapes: Spheres, needles, triangles.

Applications: Used for stainless steels, titanium and other corrosion resistant metals.

Natural media:

Materials: Coconut granules, walnut shells, corn granules.

Properties: Very delicate, suitable for light cleaning and final finishing.

Shapes: Irregular, depending on the nature of the material.

Applications: Used for cleaning delicate objects, such as electronic components and jewelry.

Synthetic media:

Materials: Polyurethane, rubber.

Properties: Can be designed with different hardnesses and shapes for specific finishing applications.

Shapes: Blocks, spheres, cylinders.

Applications: Often used in specialized applications where a combination of flexibility and controlled abrasiveness is required.

Chemical products used


Alkaline cleaners: Often based on sodium hydroxide (NaOH) or phosphates, they are used to remove oils, greases and other organic contamination from metal pieces. They may contain chelating agents such as EDTA to bind metal ions and improve scrubbing effectiveness.

Acid detergents: Based on acids such as phosphoric acid (H₃PO₄) or citric acid (C₆H₈O₇), they are used to remove oxides and other inorganic contamination. Weak acids such as citric acid are preferred for delicate metals.

Corrosion inhibitors:

Nitrites: Like sodium nitrite (NaNO₂), they work by forming a protective layer on the surface of the metal, preventing corrosion.

Benzotriazole (BTA): Used specifically for metals such as copper and brass, it forms a protective film that prevents corrosion.

Amine inhibitors: These compounds contain amines such as diethanolamine (DEA) that protect metals by forming a barrier layer against moisture and other corrosives.

Polishing agents:

Polishing paste: Contains fine abrasives such as aluminum oxides or silicon carbide in combination with chemical binders to improve the shine of surfaces.

Chemical polishing agents: Such as oxalic acid (C₂H₂O₄), which chemically react with the metal surface to improve shine.

Specific compounds:

Specific formulations may include blends of surfactants, complexants and inhibitors for particular metals such as aluminium, where chemical agents are needed to prevent oxidation and improve surface finish.

Process example

An example of vibrofinishing could be the treatment of stainless-steel components to obtain a shiny, burr-free surface. Here's how the process might go:

  1. Stainless steel components are loaded into the vibrating machine along with ceramic media and an alkaline cleaning compound based on sodium hydroxide and chelating agents.
  2. The machine is activated, and the pieces are agitated for a predetermined period of time, for example 30-60 minutes.
  3. During the process, the cleaning compound removes oils and greases, while the ceramic media smoothes the surface, removing burrs and small imperfections.
  4. After the sanding phase, a sodium nitrite-based corrosion inhibitor is added to protect the pieces during the rinsing and drying phase.
  5. Finally, if necessary, a polishing agent containing oxalic acid can be added to obtain a highly reflective surface.

Advantages of vibrofinishing

Efficiency: It allows you to treat a large number of pieces simultaneously, reducing processing times compared to other finishing methods.

Versatility: It can be used for a wide range of materials and applications, from hard metals to delicate objects.

Finish quality: It produces uniform, high-quality surfaces, improving the aesthetic appearance and functional properties of the treated parts.