In metalworking, what’s on the surface matters as much as the properties of the bulk material. Any interaction with the part’s surroundings happens on the surface, so the right finish goes a long way in yielding the desired properties and enhancing its integrity. Equipment like sandblasters or an anodizing tank can seem expensive, but there are good reasons for a manufacturer to have some in-house options.
Common Types of Metal Finishing
Broadly, metal finishing processes are used to either add layers of material on the surface, alter the metal surface or remove surface material. The former processes modify the surface properties of the part, while the latter is largely employed to clean away surface flaws and reduce surface roughness. Painting, grinding and buff polishing are some low-tech examples that many are familiar with, but others common in industry include:
- Electroplating, using a current to deposit dissolved metal ions onto a surface;
- Anodizing, inducing the formation of a protective oxide layer on non-ferrous metals;
- Sandblasting, firing sand, pellets or another abrasive at a substrate to wear it away;
- Hot blackening, heat-treating the surface to form abrasion-resistant black oxide.
Benefits of Metal Finishes
One of the most common reasons for metal finishing is improving durability. Wear and tear of metal components frequently occurs at the surface—for example, corrosion, abrasion and chemical attack. Treating the surface or depositing a protective layer can extend the lifespan of metal tools and parts exposed to regular wear. Conversely, buffing and polishing metal surfaces to make them smoother can reduce friction damage done to other surfaces by contact. These processes also often improve the aesthetic appeal of treated surfaces, restoring or modifying appearances and making for easier upkeep.
Besides preventing or treating surface damage, the right finish can alter the electrical, thermal or chemical properties of the material at the surface, useful for fabricating contacts or catalysts.
The automotive, aerospace and construction industries all benefit from being able to combine mechanical strength in steel, aluminum or titanium with resilience via metals like copper, chrome or nickel. Additionally, electronics frequently use metal plating to protect sensitive components or enable conductivity in circuitry.
Heavy industry isn’t the only place that metal finishing matters. Medical equipment needs to be reliable and hygienic, especially implants and tools used in surgery. A smooth, corrosion-resistant finish that won’t harm the body with burrs, adverse biochemical reactions or bacterial growth is vital for any of these.
Finally, shiny, smooth surfaces have visual appeal on vehicles, appliances and jewelry, and metal finishes can be used to also alter the color or texture of these surfaces.