Matt black ironmongery has gone from a niche look to a default one — black taps, black handles, black sockets. A bright stainless bolt head in the middle of it undoes the effect entirely, which is why black fixings have become a range in their own right.
They are not all the same thing, and the differences matter outdoors.
What black stainless actually is
Our black nuts and washers are chemically blackened stainless steel. The fixing is made from A2 or A4 stainless first, then treated so the surface converts to a black oxide.
The key point: the colour is a conversion of the surface itself, not a coating sitting on top. There is no film to chip off and no paint layer to peel at the edges of a spanner flat. Underneath, it is still stainless — so a scratch exposes stainless, not bare steel, and it will not bleed rust down your paintwork.
How it compares
- Black zinc / black passivated steel — cheap, and the black sits on a plating over mild steel. Once through, it rusts like any steel. Fine indoors, poor outdoors.
- Powder coated — thick, durable colour, but it builds up in threads and under heads, and it chips at corners. Awkward on fasteners specifically.
- Chemically blackened stainless — thin enough not to affect thread fit, corrosion resistance from the base metal, and no chipping. More expensive.
What it will and won't do
Be realistic about the finish. Blackening is a surface treatment measured in microns. It resists handling and weather well, but it is not armour:
- Spanner flats will polish to grey if you crank hard on them repeatedly. Use the right size and a six-point socket where you can.
- Prolonged direct sun will lighten the finish over years.
- Abrasive cleaners will take it off. Soapy water and a cloth, nothing more.
The corrosion resistance comes from the stainless underneath, so pick your grade the usual way — see our guide to A2 versus A4. A black A2 fixing on a coastal balcony will pit exactly like a bright A2 one.
What we stock in black
- Dome cap nuts to DIN 1587 — the closed acorn cap covers the thread end, so there is no bright stub poking out of a black assembly. Also the safe choice at hand height.
- Serrated flange nuts to DIN 6923 — integral washer face plus serrations that bite in and resist vibration. No separate washer needed.
- Penny / mudguard washers to DIN 9021 — oversized outside diameter to spread load on soft or oversized holes.
- Flat washers Form A to DIN 125 — the standard washer, in black.
- Finishing cup washers — countersunk cup that conceals the hole around a screw head. The detail that makes a black fixing look deliberate rather than tolerated.
Two practical notes
Buy the set together. Blackening varies slightly between production batches, more visibly than bright stainless does. If a job is visible and you need consistency, order everything at once rather than topping up in six months.
Mind galvanic pairing. Black stainless is still stainless. Bolting it to galvanised or aluminium in a wet location sets up the same galvanic problem as any stainless fixing.
Where to start
Black options sit within Nuts and Washers. For black nylon and rubber sealing washers — a different material for a different job — see Nylon & Plastic Products.