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.
