Black Oxide Ultra Concentrate

Metal chemical blackening with Galvanizing Black Oxide Ultra Concentrate

A practical solution to quickly and easily chemically blacken and protect steel and iron.

Verzinkshop Black Oxide Ultra is a newer cold black oxide system based on milder acids that gives a very dark, even black finish in minutes. It works according to the same steps as Verzinkshop Zwart Oxide, with an even darker final colour with correct post-treatment. Developed for cold chemical blackening of iron and steel with minimal impact on dimensions, ideal for steel furniture, panels, restoration projects and components, among others. Not suitable for stainless steel.

Available in:

• 100 ml makes 1 liter (tester)
• 200 ml makes 2 liters
• 400 ml makes 4 liters
• 800 ml makes 8 liters
• 1600 ml makes 16 liters
• 3200 ml makes 32 liters

Need a large quantity? Please contact us .

Key Features of Black Oxide Ultra

• coverage ≈ 10 m² per liter of concentrate (≈ 2.0 m² per 200 ml)
• Safer to use than similar products from other suppliers by using milder chemicals.
• Works on cold and hot rolled iron and steel, structural steel, alloy steel, tool steel, cast iron, forged steel. Not suitable for stainless steel.
• The process usually takes 2 to 3 minutes, up to 5 minutes.
• Must be finished with a sealer, preferably while the surface is still wet.
• Mixing ratio: Start with 1:9 (1 part concentrate to 9 parts water). Adjust if necessary: 1:6 (stronger) or 1:12 (thinner). With a brush/sponge, 1:2–1:9 or undiluted can be used. Read more about the use of different types of water here.

Features of Verzinkshop Black Oxide Ultra Concentrate

Very professional product, suitable for both professionals and hobbyists.

• Cold black-oxide system with mild acid for a very dark finish at room temperature.
• Can be mixed in different proportions for the desired result.
• Apply by immersion, or manually with brush/sponge/cotton swab.
• Has no noticeable impact on the dimensions of the workpiece, ideal for precision parts.
• Works at room temperature, at low ambient temperatures the solution may be slightly heated.

Protecting chemically blackened metal and the black oxide layer

A black-oxide conversion layer in itself has limited anti-corrosion properties. Without a sealer, the layer will further oxidize in contact with moisture and oxygen. Therefore, always apply a water-repellent sealer, preferably while the surface is still wet after rinsing.

• Galvanizing Acrylic Metal Sealer – thin, shiny, structureless acrylic lacquer for interiors.
• Verzinkshop DeepSeal Metal Sealer – oil-based sealer, dust-dry.
• Verzinkshop Uni Metal Sealer – oil-based sealer, leaves a slightly greasy film.

Blacken your own metal with Verzinkshop Black Oxide Ultra Concentrate

This product works very well on structural steel and well-cleaned steel plates and parts. It meets the principles of the Living Building Challenge Red List.

Follow the steps to get an even black-oxide finish:

1. Light the Verzinkshop Black Oxide Ultra solution in a clean plastic or glass container (start 1:9).
2. Clean and degrease thoroughly. Remove rust where necessary. Activate if necessary: dip briefly (30–60 s) in 30–50% hydrochloric acid and rinse thoroughly immediately.
3. Immerse the part in the Black Oxide Ultra solution and move the light until the desired blackness is reached (usually 2–3 minutes, up to 5 minutes). Large objects can be worked with a brush or sponge manually.
4. Rinse in a designated container (not under the tap above the bath). Do not use compressed air to dry.
5. Sealing: finish immediately with a suitable sealer while the surface is still wet.

Frequently asked questions about black oxide products

The liquid can be stored in a sealed container for several months and reused. Performance depends on hygiene, load and maintenance (replenishment/filtering).

The black-oxide finish is not rust-resistant by itself and cannot be applied without a sealer. The conversion layer continues to oxidize without a protective layer.

This product does not work on stainless steel, use the Verzinkshop Black Stainless Steel Concentrate.