Guide
Black nickel plating, black oxide or black anodize: which black finish fits your part?
Black nickel plating is a thin, dark electroplated nickel alloy, used mainly for appearance and low glare on brass, bronze, steel or zinc parts. If the part is aluminum, black anodize is usually the better black; if it is steel and needs only a dark color with oil, black oxide is simpler; choose black nickel when you want a metallic, conductive black over a nickel undercoat on a non-aluminum part.
By Saola Manufacturing engineering team · Published · Updated
This guide compares the three finishes buyers most often mean when a drawing just says “black”. How to write the black oxide note itself is covered in the black oxide callout guide, so it is only summarized here.
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What is black nickel plating, chemically?
It is not pure nickel: it is an electroplated nickel alloy, commonly nickel-zinc, that comes out dark gray to black. Because the layer is thin and somewhat brittle, it is treated as a decorative finish rather than a protective one.
Plating chemistry makers sell nickel-zinc and nickel-cobalt-zinc versions. The result is a dark, metallic-looking film whose depth of color depends on bath chemistry and on what sits underneath it. Plating chemistry makers describe their black nickel layers as very thin; one maker's technical page gives a layer of up to 2 microns by rack or barrel (Uyemura, black nickel process data), and the same page says a heavy nickel undercoat is used when higher corrosion performance is wanted.
That undercoat is the key design fact. Black nickel on its own adds color, not a barrier. The corrosion resistance of a black nickel part comes almost entirely from the bright or semi-bright nickel (and sometimes copper) layers below it, plus any clear lacquer or oil applied on top. When you compare quotes, you are really comparing the whole stack, not the black layer.
The old U.S. military specification for this finish, MIL-P-18317, dates from 1954 and covers black nickel on brass, bronze or steel for uses such as the interior of optical instruments, where the operator's vision should be distracted as little as possible (MIL-P-18317 record, EverySpec). A standards store lists a 2020 cancellation notice for it that points future buys to SAE AMS-QQ-N-290 (NSAI standards store listing), so check the status in the DoD ASSIST database before you cite it on a new drawing.
How do black nickel, black oxide and black anodize compare?
They differ in what base metal they go on, whether they add thickness, whether they conduct, and how much corrosion protection they give. The table sorts them on the points that usually decide the choice.
Read the table by base metal first. Anodizing only works on aluminum (and a few other valve metals), black oxide is a conversion of the surface of steel, stainless or copper alloys, and black nickel is an electroplate that can go on most metals a plater can prepare, including brass and zinc die castings.
| Point | Black nickel plating | Black oxide | Black anodize (dyed) |
|---|---|---|---|
| Base metals | Brass, bronze, steel; also zinc die castings and other platable metals | Steel, stainless, copper alloys | Aluminum alloys only |
| How it forms | Electroplated layer, usually over a nickel undercoat | Chemical conversion of the surface | Electrolytic oxide grown from the aluminum, then dyed and sealed |
| Dimensional change | Black layer is very thin; the undercoat adds measurable thickness | Typically no measurable change | Coating grows partly into and partly out of the surface |
| Corrosion protection | Set by the nickel undercoat and topcoat | Very limited without oil or wax | Good when sealed |
| Electrical conductivity | Metallic stack is conductive | Thin film; contact usually still possible | Oxide is an electrical insulator |
| Look | Metallic dark gray to black; can be glossy | Matte to semi-gloss black, oily feel if oiled | Even black, matte to satin |
| Wear | Soft black layer can mark on sliding contact | Wear set by the base steel | Hard oxide; Type III is harder still |
When should a drawing call for black nickel?
Use it when the part is not aluminum, needs a metallic black look, and must keep a conductive surface or already carries nickel plating for corrosion. Brass and zinc parts that people see and handle are the common case.
Typical candidates are decorative brass fittings, knobs, bezels, hardware and instrument parts, and zinc die-cast housings that already go through a copper-nickel plating line. On those parts the black layer is a short extra step at the end of a line the part was going through anyway.
Black nickel is a poor fit for three cases. On aluminum, anodize is lighter work and better protection. On sliding or wearing surfaces, the thin black film can burnish to a lighter color, so keep it off bores and shafts or accept that those areas will change shade. On parts that must survive outdoor or marine exposure without a topcoat, the finish depends on the undercoat and lacquer, so you would be specifying those layers anyway.
Many buyers asking for black nickel on stainless steel really want a black that does not rust. For stainless, black oxide is the usual low-cost route, and the black oxide guide explains which class applies.
When is black oxide or black anodize the better choice?
Pick black oxide for steel parts that must keep tight fits and live indoors with oil, and pick black anodize for any aluminum part. Both are usually simpler to buy than a plated stack.
Black oxide adds essentially no thickness, so a ground shaft or a threaded hole keeps its fit. Its weakness is corrosion: MIL-DTL-13924E states in its scope that black oxide gives only very limited corrosion protection under mildly corrosive conditions (MIL-DTL-13924E, 2018), so the oil or wax topcoat and the packaging do most of the work.
Black anodize is the default black for aluminum. It is an oxide grown from the part itself under MIL-A-8625F, which covers six types and two classes of anodic coating (MIL-A-8625F, 1993); black is a dyed Class 2 finish. Because the oxide insulates, plan masked or machined-after areas where the part must ground, as the anodize conductivity guide explains, and see the black anodize guide for color and fade control.
How do you write a black nickel callout on the drawing?
Name the whole stack: base metal preparation, undercoat type and minimum thickness, the black layer, any topcoat, the significant surfaces, and the appearance standard. A note that only says BLACK NICKEL leaves every one of those choices to the plater.
A workable generic note, to adapt rather than copy:
FINISH: BRIGHT NICKEL UNDERCOAT [MIN THICKNESS] ON SIGNIFICANT SURFACES, THEN BLACK NICKEL. CLEAR LACQUER TOPCOAT [YES/NO]. COLOR AND GLOSS TO MATCH APPROVED SAMPLE [ID]. NO PLATING IN THREADS [LIST] / THREADS TO GAUGE AFTER PLATING.
Put a number on the undercoat only if you have a basis for it, such as a nickel plating standard your product already uses for its other plated parts (the electrolytic vs electroless nickel guide covers ASTM B689 and related specifications). Mark the significant surfaces on the drawing, because recesses and blind holes plate thinner and may come out lighter in color. Treat color as a sample-approval item: black nickel shade varies from bath to bath, so an approved boundary sample is the practical acceptance standard.
For threads, decide whether the plated stack must fit a standard gauge after plating. If it must, say so; the machinist then cuts the thread to allow for the plating. The threads after anodizing and plating guide walks through that allowance.
How do you inspect and accept a black nickel part?
Accept it on appearance against the approved sample, undercoat thickness on a test location, adhesion, and thread or bore fit after plating. Ask the plater to report each of those for the lot.
Appearance is checked by eye under agreed lighting against the boundary sample. Thickness is normally measured on the undercoat, because the black layer is too thin to matter dimensionally; the coating thickness measurement guide explains which gauge suits which stack. Adhesion is usually a bend or tape-style check on sample parts, and fit is checked with go/no-go gauges on plated threads and bores.
In the RFQ, ask the supplier to state the undercoat, the black process, the topcoat, and what the certificate of conformance will list. Also ask whether the bath is a nickel-zinc type or another black nickel chemistry, since that affects RoHS questions and color.
How is a black finish handled on a Saola order?
Finishing at Saola is a managed process run by partner plants, from a fixed menu. Electroplating is on the menu in general, but black nickel is not a named item on it and black oxide is not on it, so raise either at drawing review; anodizing on aluminum is on the menu.
Our lead plant in Vietnam machines the part on its CNC turning and CNC milling lines. The finish is applied by a partner plant we manage, and the quote names where each step is done.
The current menu on the surface finishing page covers electroplating, gold plating, zinc plating, RoHS blue trivalent chromate, oil-dip rust protection, anodizing on aluminum, powder coating and pad printing. If your drawing calls for black nickel or black oxide, flag it in the RFQ so it is reviewed against that menu before any price is given. For aluminum parts, a black anodize callout can be quoted from the menu once the color sample and masking are defined. Send the drawing for a quote with the finish note written the way you intend it.
Frequently asked
Is black nickel the same as black chrome?
No. Both are dark electroplates usually laid over a nickel undercoat, but they come from different baths and differ in color, hardness and process. Treat them as separate callouts and approve a sample of whichever one you choose.
Can black nickel go directly on aluminum?
Not directly in normal practice. Aluminum needs special preparation, such as a zincate step, before any nickel will adhere, and for most aluminum parts black anodize is the simpler black. Raise any plated black on aluminum at drawing review.
Does black nickel conduct electricity?
The plated stack is metallic, so it is generally conductive, unlike anodize. If the part must carry a ground or contact current, say so on the drawing and test a sample, because a lacquer topcoat will insulate the surface.
Will black nickel change my thread or bore size?
The black layer is thin, but the nickel undercoat adds thickness. Either mask the feature or have it machined to allow for the plated stack, and state that the thread must gauge after plating.
Is black nickel RoHS compliant?
It depends on the bath and any sealer. Many black nickel baths contain no restricted substances, but ask the supplier for a RoHS declaration on the finished stack rather than assuming it.
Sources
- MIL-P-18317, Plating, Black Nickel (Electrodeposited) on Brass, Bronze, or Steel, U.S. Department of Defense, December 22, 1954 (EverySpec record)
- MIL-P-18317 Notice 1, Cancellation, listing by NSAI standards store, 2020
- Black Nickel / Ruthenium Plating Processes, Uyemura (plating chemistry maker), technical page accessed November 2026
- MIL-DTL-13924E, Coating, Oxide, Black, for Ferrous Metals, U.S. Department of Defense, September 12, 2018
- MIL-A-8625F, Anodic Coatings for Aluminum and Aluminum Alloys, U.S. Department of Defense, September 10, 1993