Removing Oxidation With Tumbling

Many metals (aluminum, copper, iron, steel) are attacked by air to create undesirable surface oxidation. While oxidation can be beneficial and protect the surface (note the green color of the Statue of Liberty) often this oxidation needs to be removed. While abrasive blasting is highly recommended for this process, large quantities of small parts can be difficult to blast one at a time.

Vibratory or barrel tumbling the parts in an abrasive or polishing media can quickly and effectively remove oxidation and prep a surface for further processing. In combination with the appropriate chemical compounds choosing the right type of media is important. Using an abrasive media will typically produce a clean, matte surface finish. Polishing media will enhance the compound cleaning action to leave a bright surface finish.

A mild acid cleaner designed for tumbling is an ideal choice for gentle oxidation removal. While more aggressive acids (mineral acids like muriatic) will also remove oxidation, care should be taken not to attack the underlying metal. In a pinch, a quick additive to use would be something like vinegar (acetic acid), citric acid or oxalic acid products (consumer bar cleaners).

The Uniqueness of Glass Bead

Glass bead is unique among blasting media. The combination of round shape and hardness produces a surface effect that is unlike other blasting grit. Abrasive media are designed to strip materials or create a surface profile. These angular media are designed to be aggressive on the surface for short and effective blast cycle times.

Glass bead is typically used for peening applications. While most media are blasted at an angle to the surface, glass bead is generally blasted perpendicular to the blast area. In combination with the round shape and hardness, this method creates a very uniform and very smooth surface finish. The size of the bead used and the hardness of the metal being blasted will result in a final surface aesthetic ranging from extremely uniform and matte to a bright, peened, satin-like finish.

Deburring Small Slots

Choosing the proper tumbling media is critical when the geometry or configuration of a part provides a specific challenge. Elements like holes, grooves and slots often can only be deburred with a unique media shape and size.

The slot in this stainless steel part is only 0.050" wide. Choosing a media that is too large may not 'attack' the burr at all but simply roll it inside. A media that is very small (like an abrasive grit) may get into the slotted area but not with enough mass to deburr the edge or could get stuck inside the part.

The long, thin shape of this slot can be deburred using a media with a angled edge. A ceramic angle cut cylinder (ideally 45 degree) with a diameter less than 1/4" will deburr the inside edge of the slot without getting stuck in the part. Alternatively, a small precision media such as a 4 mm (0.15") abrasive triangle will be able to fit inside the slot.

The part geometry and the tumbling demands (deburring, polishing, etc.) will determine the media that will best provide the desired results. Take a close look at your parts as there may be alternatives that will provide better, faster and even more cost effective results.

Deflashing Plastic Parts

Molded plastics often contain flashing that needs to be removed. While there are many methods ranging from a sharp knife to cryogenic deflashing, vibratory tumbling is an effective and cost efficient method.

Flash sticking above edge
Flashing removed - smooth edge, matte finish


The part was vibratory tumbled with Ceramic Media for only 30 minutes. A non-abrasive tumbling compound solution was used to keep the process lubricated and clean. Even after this short cycle time, the flashing was completely removed and the edge was smooth. The surface had matte, tumbled finish. At a 30 minute cycle time the general purpose media should be able to be re-used for 250 or more batches to spread the operating cost over many parts.

Choosing Tumbling Media

Choosing the proper tumbling media (vibratory tumbling or barrel tumbling) for any deburring, deflashing or polishing application requires balancing the aggressiveness of the operation with the surface finish specifications. As long as a rough, tumbled appearance is acceptable a more aggressive media can be used to remove burrs and 'smooth' a surface resulting in a shorter cycle time . If the surface finish is important (i.e., for anodizing or thin-coat plating), a less aggressive media and longer cycle time is necessary. Often a multi-step process is used with progressively less aggressive media to achieve a deburred and smooth part or even polished part.

Generally, Ceramic Media are used on harder metals like steel or titanium. Plastic or Synthetic Media are better for softer metals like aluminum, brass and copper. Within each type of media, a variety of formulations (or bonds) are available from ultra aggressive to general purpose to polishing.