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Ultra-Blak 420

For Industrial Use

Ultra-Blak 420 is an oxidizing liquid formulated for blackening a variety of brass, bronze, copper, and copper-alloyed surfaces.

One gallon can blacken 100–300 sq. ft. of copper parts.

How to Use Ultra-Blak 420

Use Ultra-Blak 420 to apply a deep black finish with excellent abrasion resistance to brass, bronze, copper, and copper-alloy surfaces.

Use Ultra-Blak 420 to:
  • Give copper, brass, and bronze parts a deep, black finish
  • Produce a true copper oxide finish, US 10 B
  • Achieve superior abrasion resistance
  • Work with a hot-temperature blackening process

Safety & Technical Data

The Blackening Process: Ultra-Blak 420

For the longest-lasting, deepest, and cleanest black finishes, we recommend the following blackening process. Please read all safety data sheets and technical data sheets prior to beginning a project.

1. Clean

Soils such as cutting oils, coolants, lubricants, and rust inhibitors must be removed from the metal workpiece. Soils can inhibit the blackening process and negatively affect coating adhesion and appearance. Thoroughly clean and degrease the parts for 5–10 minutes prior to beginning the blackening process.

Recommended Cleaning Products:

2. Rinse

After cleaning the metal parts, rinse them in cold, overflowing tap water; it’s necessary to rinse the parts to remove residual cleaning solution. Parts carrying over un-rinsed film of alkaline cleaning solution would quickly contaminate the subsequent chemicals in use, resulting in a spotty or non-adherent black finish. 

Immerse the parts to be blackened for 30–60 seconds.

3. Deoxidize

Immerse parts in a solution of muriatic acid (25–50% by volume) for 30–60 seconds at room temperature. Alternatively, parts can be deoxidized in a solution of E-Pik 215 or E-Pik 217 (1–2 pounds per gallon).

4. Rinse

Rinse in cold, overflowing tap water for 30–60 seconds.

5. Blacken

Immerse parts in a solution of Ultra-Blak 420 for 5–20 minutes until a deep black color develops. The solution should be kept at 140–200° F throughout the blackening process.


*Note that if the parts are high zinc (15–35%) copper alloys, they must be activated before blackening. This does not apply to copper or bronze parts. See technical data sheet for more information.

6. Rinse

Rinse in cold, overflowing tap water for 30–60 seconds to remove residual blackening solution and ensure sealant will not be contaminated.

7. Seal

Seal the black-oxide finish by immersing the still-wet parts in a corrosion-inhibiting and rust-preventative solution. E-Tec corrosion inhibitors are formulated to rapidly displace the residual acidic solution from the preceding rinse and produce long-term corrosion protection. As the E-Tec is absorbed, it enhances the depth of black, which may take several hours.

Recommended Sealing Products:
  • E-Laq 525 creates a hard, dry, and glossy finish.
  • E-Tec 510 is a water-soluble oil that’s slightly oily.
  • E-Tec 504 is a solvent-based oil that results in a thin, dry film.