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Surface Finish Selector

Find the right surface finish for your CNC part. Select your application type, material, budget, and priority. The tool ranks 12 finishes and highlights the best match for your needs.

Your Requirements

Recommended Finishes

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Specify your finish in the order notes. Free DFM review included.

Recommendations based on general industry guidelines. Actual suitability depends on your specific application.

How We Calculated This

This tool scores each of 12 surface finishes against your inputs. It checks material compatibility first, then scores each finish on four criteria: how well it matches your application type, whether it fits your budget, how well it aligns with your priority, and overall versatility.

Material Compatibility

Not every finish works on every material. Anodize only works on aluminum and titanium. Black oxide works on steel and stainless. Passivation is for stainless steel only. The selector filters out incompatible finishes so you only see options that work with your material.

Application Scoring

Each finish gets a score from 0-10 for each application type. For example, electropolish scores 10 for medical because it creates an ultra-clean, smooth surface. Powder coat scores 10 for cosmetic because it offers the widest color range. The tool uses these scores to rank finishes for your use case.

Budget and Priority

Budget filters finishes by cost level. A low budget favors as-machined, bead blast, and passivation. A high budget opens up electropolish, chrome plate, and hard anodize. Your priority further adjusts the ranking. Choosing "durability" boosts hard anodize and nickel plate. Choosing "lead time" boosts finishes with no extra processing time.

Pro tip: If you are not sure what finish to use, start with as-machined for prototypes. You can always add a finish later for production parts. This keeps prototype costs low and turnaround fast.

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Frequently Asked Questions

As-machined is the cheapest finish because it requires no secondary processing. The part comes straight off the CNC machine with tool marks visible. Ra is typically 32-63 microinches. For a low-cost secondary finish, bead blasting adds a uniform matte texture for minimal cost.
Type II anodize creates a thin oxide layer (0.0002-0.001″) that adds color and moderate corrosion protection. Type III hard anodize creates a thicker, harder layer (0.001-0.003″) that adds significant wear resistance and hardness up to 70 Rc. Type III costs about 60% more and is used for high-wear applications.
No. Anodizing only works on aluminum and titanium. For stainless steel corrosion protection, use passivation (removes free iron) or electropolishing (smooths and brightens the surface). For color on stainless, use powder coating, nickel plating, or black oxide.
Medical devices typically require electropolishing (for stainless steel and titanium) or passivation. Electropolishing creates an ultra-smooth surface that resists bacterial adhesion and is easy to clean. For aluminum medical housings, Type II anodize with a clear or colored finish is common.
Ra stands for Roughness Average, measured in microinches. It is the average height of surface peaks and valleys. Lower Ra means smoother surface. As-machined is 32-63 Ra. Fine machined is 16-32 Ra. Mirror polish is 4-8 Ra. Most functional parts work fine at 32-63 Ra.
Powder coating typically adds $8-25 per part depending on size. It adds 2-3 days to lead time. Powder coat provides excellent color options, UV resistance, and a durable finish. It works on steel, aluminum, and brass but not on plastics or titanium.
For aluminum outdoor parts, Type III hard anodize or powder coat provides the best protection. For steel, powder coat or nickel plating prevents rust. For stainless steel, passivation is usually sufficient. Titanium and PEEK need no finish for outdoor use.
Yes. Anodize Type II adds 0.0002-0.001″ per side. Type III hard anodize adds 0.001-0.003″ per side (50% grows outward, 50% penetrates). Nickel plating adds 0.0002-0.002″. Powder coat adds 0.001-0.003″. Account for this in your design if tolerances are tight.
Yes. Common combinations include masking certain areas during anodize to leave bare aluminum for electrical grounding, or anodizing then adding a powder coat on specific surfaces. RivCut can handle multi-finish parts with masking specifications on your drawing.

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