A finish callout that just says "passivate" or "polish" leaves out the part that actually matters: what property the finish is supposed to change, and whether the base material even supports it. Finish compatibility depends on the substrate — passivation and electropolishing are tied to stainless steels, anodizing applies to aluminum, and PVD or DLC choices depend on the base material along with the wear and friction requirements of the feature. Picking a finish is really picking which of those properties the part needs — corrosion resistance, wear resistance, low friction, or simply a clean evaluation-ready appearance.

Corrosion resistance: passivation and electropolishing

Passivation is the standard route to corrosion resistance on stainless steel, and it's a common next step after machining for stainless components headed into surgical or implant use — the same pattern described in CNC turning for orthopedic implant components. Electropolishing goes further, producing a smooth, clean finish on stainless steel where surface condition matters as much as corrosion resistance, such as instrument features that will be handled or inspected closely. Both are also the natural next step once a tight-tolerance feature has already been machined, EDM'd, or ground to size — see wire EDM vs. precision grinding for how those processes set up the surface a finish is then applied to. Passivation and electropolishing are covered under surface finishing, alongside the rest of the material-to-finish pairing.

Wear and friction: PVD, DLC, and anodizing

Where a feature needs to resist wear rather than corrosion, the finish options change. PVD coatings add a hard, wear-resistant film; DLC (diamond-like carbon) targets low friction on top of that same wear resistance. Type II and hard-coat anodizing serve the equivalent role on aluminum, since anodizing doesn't apply to stainless the way passivation and electropolishing do. These are the finishes worth specifying for wear-oriented instrument features and low-friction interfaces — the kind of application detail worth checking against the full grade table on the materials page before locking in a substrate, since the finish that's available depends on which alloy is underneath it.

Cosmetic and evaluation finishes

Not every finish is load-bearing. Bead blasting produces a matte, satin, or bead texture, and brush or mirror polishing does the cosmetic work of bringing a part to an evaluation-ready appearance. Both matter for orthopedic part surfaces and cosmetic evaluation parts, and both matter for parts headed into a trial fit or assembly check, where how a part looks and handles is part of what's being evaluated alongside how it mates.

Specify the property, not just the process name

The fastest way to get the right finish is to name what it needs to do — resist corrosion, resist wear, run with low friction, or simply look evaluation-ready — rather than guessing at a process name. When the right pairing isn't obvious, that's a material-selection question as much as a finishing one; matching material properties, strength, and finish to the application is exactly the kind of thing worth raising before the substrate is locked in, not after. Include the finish requirement, along with the base material it applies to, on the RFQ checklist, or send the drawing and finish requirement through the contact page.