The short answer
For wear surfaces on CNC aluminum (and some steels for EN), buyers often choose **hard anodize (Type III)** versus **electroless nickel (EN)**. They solve different wear/corrosion stories and change masking, growth, and [quote-new.php](https://3dwk.com/quote-new.php) **rates.v1.1** estimate packaging. Pick one primary wear system—do not stack both “everywhere” without function.
This guide is for buyers finishing functional slides, cams, and housings. Illustrations use an **Example part** only. It is distinct from Type II vs Type III cosmetics in [anodizing Type II vs Type III](https://3dwk.com/resources/anodizing-type-ii-vs-type-iii) and from plating family overviews in [zinc vs electroless nickel vs black oxide](https://3dwk.com/resources/zinc-plating-vs-electroless-nickel-vs-black-oxide).
What each finish is good at
**Hard anodize (Type III):** thick aluminum oxide on aluminum alloys—wear resistance, dielectric benefits, limited color options. Growth into fits matters; call post-anodize skim or pre-size. See [how anodize choice changes CNC RFQ cost](https://3dwk.com/resources/how-anodize-choice-changes-cnc-rfq-cost) and [chem film vs Type II anodize](https://3dwk.com/resources/chem-film-vs-type-ii-anodize-aluminum).
**Electroless nickel:** conformal Ni-P coating on aluminum or steel—wear + corrosion, more uniform thickness on complex geometry than rack electroplate. Call required thickness class and whether high-phos or mid-phos matters for your environment.
Neither is a universal “make it tougher” stamp. Soft Type II clear on cosmetics does not replace a wear callout on a sliding bore. Powder coat is a different family entirely—see [powder coating vs painting](https://3dwk.com/resources/powder-coating-vs-painting-metal-parts).
Wear callouts that shops can price
State: mating material, motion type (slide / rotate / occasional), dry or lubricated, and which faces need the wear system. “Hardcoat all over including threads” forces masking notes and often widens bands. Mask threads, grounding pads, and press-fit IDs explicitly. Related: [edge break / chamfer / deburr](https://3dwk.com/resources/edge-break-chamfer-deburr-callouts-cnc), [thread inserts vs tapped holes](https://3dwk.com/resources/thread-inserts-vs-tapped-holes-aluminum), [designing threads](https://3dwk.com/resources/designing-threads-and-tapped-holes).
Illustration 1 shows an **Example part** wear-face map: hard anodize on slide ways versus EN on a steel cam profile—typical guidance, not a customer lab report.
Dimensional growth and sequence
Type III growth can be tens of microns per surface depending on target thickness—design fits accordingly or call post-finish machine. EN thickness is more uniform but still consumes tolerance budget on H7 bores. Sequence notes (“machine → EN → skim seal face”) prevent false automatic mids. Background: [surface roughness Ra](https://3dwk.com/resources/surface-roughness-ra-for-machined-parts), [reaming vs boring](https://3dwk.com/resources/reaming-vs-boring-cnc-hole-size), [O-ring groove design](https://3dwk.com/resources/o-ring-groove-design-cnc-housings).
Cost and lead-time narrative (estimates)
Finish lot minimums often dominate prototype qty. A qty 2 Type III line can carry nearly the same finish adder story as qty 10 if finish-bound. **rates.v1.1** CNC material/time bands still apply underneath (e.g. PA66 bar ~$5/kg coeff ×0.8; 17-4PH ~$9/kg ×1.4; IN718/IN625 ~$55–60/kg ×2.5; CoCr ×2.2—estimates). Hard anodize is aluminum-centric; EN on hot alloys may push lines toward **needs_manual** when combined with high machine time or line totals above configured USD thresholds. See [what needs_manual means](https://3dwk.com/resources/what-needs-manual-means-preliminary-quote) and [how quantity breaks change CNC unit cost](https://3dwk.com/resources/how-quantity-breaks-change-cnc-unit-cost).
Illustration 2 contrasts “wear coat somehow” versus a finish-block RFQ with masked threads and growth notes.
When to prefer hard anodize
- Aluminum substrate
- Sliding aluminum-on-polymer or light metal contact
- Electrical isolation needs
- You can tolerate or machine for oxide growth
When to prefer electroless nickel
- Need coating on steel or mixed metals in one process family
- Complex OD/ID needing uniform thickness
- Corrosion + wear together
- Hard anodize is not applicable (non-aluminum)
Substrate and alloy notes
6061 and 7075 both hard-anodize, but dye and wear narratives differ—state alloy. Steels take EN, not Type III. Stainless may prefer passivation/electropolish for corrosion without a wear coat—see [passivation vs electropolishing](https://3dwk.com/resources/passivation-vs-electropolishing-stainless). Do not paste aluminum hardcoat notes onto a 17-4PH RFQ.
Example part walkthrough
**Example part:** 6061-T6 wear plate, ~100×60×8 mm, two Ø8 H7 hinge bores, sliding face Ra 0.8 target after finish. Path A: Type III on slide face only, mask bores, pre-size for growth. Path B: mid-phos EN 25 µm nominal on slide + edges, mask threads. Upload the chosen path on [quote-new.php](https://3dwk.com/quote-new.php)—do not invent salt-spray certificates or customer logos.
What to do next
Pick one wear system, mark masked faces, then estimate on [quote-new.php](https://3dwk.com/quote-new.php). Service pages: [CNC machining](https://3dwk.com/cnc-machining-service.php), [materials](https://3dwk.com/materials.php). **rates.v1.1** figures are planning estimates. If needs_manual appears, clarify finish scope rather than stacking every coating name on the drawing.
Masking maps buyers should draw
A one-page masking sketch on the PDF—shade wear faces, cross-hatch mask zones—beats a paragraph of prose. Shops price masking labor from clarity. Grounding pads, press-fit IDs, and tapped holes are classic mask zones; leaving them ambiguous invites clarification loops that look like **needs_manual** even when spindle time is simple. Related service path: [CNC machining](https://3dwk.com/cnc-machining-service.php).
Prototype versus production finish stories
Qty 2 may accept a wider thickness range and visual inspection. Qty 50 may need thickness coupons, adhesion checks, or defined sampling. Say which story applies so finish vendors are not over-specified on a fit-check lot. Re-upload when the finish story changes rather than pasting an old mid onto a new quality agreement.
Common questions
Can I hard anodize then electroless nickel the same aluminum part?
Sometimes for special stacks—but call the sequence and purpose. Blanket dual coats without function inflate masking and review time.
Does Type III always beat EN on wear life?
Depends on counterface, load, and lubrication. Specify the duty; do not treat hardness numbers alone as a PO guarantee.
Will “anodize or nickel, you choose” speed the quote?
Usually the opposite—it forces clarification. Prefer one primary finish on the PDF.
Is bead blast compatible with either wear system?
Often as a pre-texture—call it explicitly so cosmetics do not overwrite wear thickness notes. Related: [bead blast vs tumble vs vibratory](https://3dwk.com/resources/bead-blast-vs-tumble-vs-vibratory-finish).