Surface Finishes

What finishing does for a machined part

A machined part is rarely finished when it comes off the machine. The raw surface can corrode, wear, hold contamination, or simply look unfinished. Surface finishing changes that. Corrosion-resistant finishes such as passivation and electroless plating protect the metal from its environment. Wear-resistant finishes such as hard chrome and heat treatment protect surfaces that rub or carry load. Appearance finishes such as anodizing and powder coating give the part color and a clean, uniform look. Functional finishes such as electropolishing smooth the surface where hygiene or flow matters. Finishing is part of the part’s design, not an afterthought, because the finish interacts with tolerances, threads and mating surfaces: a coating adds build-up, a blast changes surface roughness, and heat treatment can shift dimensions. Choosing a finish is therefore a design decision, not a last step, and it is best made alongside the material and the tolerance call-out. This page is the hub for the finishing axis — the child pages below each cover one finish in detail, while these sections explain how to specify a finish and how we deliver it. If you already know the finish you want, jump straight to its page; if you are deciding, read on.

How to specify a finish on a drawing

Write the finish on the drawing the same way you write a dimension. Name the finish, state which surfaces it applies to, and give the requirement that matters — thickness or build-up, color, or surface roughness as an Ra value. Flag any surface that must stay unfinished, and call out masking for threads, sealing faces and tight bores. Material matters as much as the finish: an anodize that works on aluminium does not apply to steel, and passivation is specific to stainless. If the drawing leaves the finish open, tell us the environment the part will see and we will recommend one during DFM. The clearer the call-out, the fewer surprises on the sample, so we treat an ambiguous finish note the way we treat an ambiguous dimension — we ask before we cut. Our drawing requirements page shows the level of detail that keeps a quote fast and accurate.

Choosing between the finishes we offer

The right finish starts with the substrate. Aluminium parts typically take anodizing, conversion coating, or powder coating. Steel parts take black oxide, zinc or nickel plating, or heat treatment. Stainless parts take passivation or electropolishing. Brass, copper and titanium each have their own suitable finishes. Beyond the substrate, the choice turns on what the part has to do: resist corrosion, resist wear, present a certain appearance, or offer a clean, low-friction surface. Because every finish changes the part slightly, we pair each recommendation with masking and allowance guidance, and we confirm the thickness or build-up against your tolerances before we run it. Match substrate to finish on our materials page, and see our tolerances page for how allowance and masking protect critical dimensions. If you are not sure which finish to pick, send the drawing and we will specify it in the quote.

How finishing is handled

Finishing runs through our vetted partner network, managed under one quality process. You place one order, deal with one point of contact, and receive one shipment — the machining and the finishing are both answered for by our factory in Qidong City, Jiangsu Province, China. The finish is quoted within 24 hours together with the machining, and it sits inside the same schedule: samples in 5–10 days and production in 25–35 days after approval. Finished parts ship with a material certificate (MTR) and pre-shipment photos. Heat treatment, plating, anodizing and the mechanical finishes in this section are all handled the same way, so a part never has to leave one hand-off chain to reach its finished state. To start an order that includes finishing, see our factory or request a quote.