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Kool-Blak 225

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Kool-Blak 225 is a blackening solution that replaces hot black-oxide processes without producing hazardous fumes, sacrificing aesthetic appeal, or reducing abrasion resistance. Drag out 1–5 gallons of Kool-Blak 225 per 100-gallon bath per week.

Learn about EPi's trial kit and the short run kit.

Samples available to purchase - CALL #262-786-9330.

PLEASE NOTE: Orders ship within 3 business days.

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How to Use Kool-Blak 225

Kool-Blak 225 is a mid-temperature black-oxide solution that gives steel parts glossy black finishes while eliminating the hazards of caustic fumes and boiling temperatures.

Use Kool-Blak 225 to:
  • Coat steel parts with a glossy, smut-free black-magnetite finish
  • Reduce safety hazards and energy costs
  • Eliminate caustic fumes
  • Work with stable chemicals
  • Meet military specification MIL-DTS 13924D Class 1 and AMS 2485L
Getting Started

EPi offers half-liter starter kits for getting acquainted with Kool Blak 225 and 5-gallon short-run production kits for small projects or operations. Learn more about what is included in the trial kit and the Short Run Production Kit.

The Blackening Process: Kool-Blak 225

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. Clean the parts for about five minutes prior to beginning the blackening process.

Recommended Cleaning Products:
  • E-Kleen SR 102 is a non-silicated liquid soak cleaner that splits and floats oils.
  • E-Kleen SR 102-E is a non-silicated liquid soak cleaner that emulsifies soils and oils.

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. Pickle

Run freshly rinsed part in an acid pickle of hydrochloric acid (50% by volume) for about five minutes.

4. Blacken

Immerse the steel part for 15–45 minutes at 220–255º F in a Kool-Blak 225 solution (see technical data sheet for titration options).


If Kool-Blak 225 isn't quite what you’re looking for, consider these similar products:

  • Ultra-Blak 400 is a premium-grade powdered oxidizing agent that produces a deep anthracite-black finish on steel and steel alloys.
  • Ultra-Blak 404 is an oxidizing salt used to give steel a deep, rich black finish.

5. Rinse

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

6. Seal

Seal the black-oxide finish by immersing the parts for one minute in a compatible E-Tec rust preventative. The 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.

See the rust preventative and sealing comparison chart to find the best E-Tec solution for your needs.

Recommended Sealing Products:
  • E-Tec 501 is a slightly oily lubricant and rust/corrosion inhibitor for ferrous and non-ferrous metals.
  • E-Tec 510 is a rust-preventative water-soluble oil concentrate that creates a soft, dry film. Corrosion resistance and other characteristics are determined by length of exposure.
  • E-Laq 525 is a clear acrylic lacquer that results in a hard, dry film. It increases hardness, durability, and wear resistance.