5 Common Metal Surface Finishes

Custom metal manufacturing requires well-planned engineering down to the finest detail; proper material choices, dimensions, and tolerances all play a critical role in ensuring that a final part or component works according to exact application requirements.

In addition to these standard specifications, the overall finished texture of the metal, or surface finish, is key to a part’s final function.

What is a Surface Finish?

Also referred to as surface roughness, surface texture, or surface topology, a surface finish broadly indicates the overall textural quality of a finished metal surface. Surface finish is often broken down into particular characteristics such as lay, waviness, roughness spacing, profile, and overall surface roughness (or friction).

Depending on a component’s specific end usage, required surface finishes will vary greatly. For example, optical and medical-grade components typically require the finest polishing and finishing available, while other, less sensitive parts may not dictate the need for such high finishes.

Popular Surface Finishes

There are nearly as many unique textures, patterns, lays, and levels of surface finish roughness available as there are applications demanding them. For designers, the goal is to balance a part’s most efficient production with required final performance, allowing for the coarsest finish possible that will still ensure optimal part quality and reliability.

Five of the most common finishing processes are listed below.

Glass Beading, which blasts a weld or surface area with glass beads ranging from 60 to 90 sieve. The resulting finish is a satin texture, much like a 2B finish, which can be applied full-surface or in masked bands.
Passivation, which creates a surface film to protect against chemical reactivity. Passivation can be the result of a number of different processes and is deeply prized for its resulting low corrosion rates.
Grinding, one of the most popular finishing methods, is an efficient way to obtain basic roughnesses. Depending on the specific tools, work style, and time applied, machinists can obtain a broad Ra (Roughness average) spectrum using grinding processes.
Mechanical Metal Polishing, a removal or buffing process, utilizes progressively finer abrasives to achieve precision smoothness. Mechanical polishing is a common sanitary polishing style, achieving surface finishes to meet 3A standards and higher.
Electropolishing, an inverse process to electroplating, streamlines metallic surfaces on a microscopic level with chemical solutions. The object at hand is polished ion by ion, creating bright, clean, and microscopically smooth results.

Specialty Metal Finishes for Unique Applications

Specific applications demand particularly high-performance finishes. Some of the most common specialty metalwork is found in medical, aerospace, and custom décor applications. A few of the most popular specialty finishes are listed below.

Sanitary Finishes, Ra ranges from 30 to 35 microinches. A sanitary stainless steel finish prevents bacterial growth and allows for efficient washing and cleaning in food manufacturing and processing, restaurant environments, beverage applications, and more.
Fine Finishes, Ra ranges from 12 to 16 microinches. A fine finish is critical for most medical and pharmaceutical applications, as well as aerospace jobs. Fine metal surfaces prevent corrosion and improve durability and overall structural fit, form, and integrity.
Mirror Finishes, the most difficult Ra to achieve. Custom architecture, design, décor, and optics all utilize mirror-finished metal for high-end projects.

Custom Metal Finishing for Your Next Project

Whether making use of grinding, honing, lapping, polishing, or superfinishing techniques, the world of custom metalwork serves many unique surface needs. The full scope of finish possibilities is at your fingertips, so be sure to partner with a trusted, experienced finishing service provider who can guide you through each step of the process.

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