The Blackening Process: Ultra-Blak 400-L
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.
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 5–10 minutes prior to the next step.
Recommended Cleaning Products:
- E-Kleen SR 102 is a non-silicated liquid soak cleaner that splits and floats oils.
- E-Kleen SR 196 is a silicated, non-emulsifying soak cleaner for that floats oil and eliminates carbon smut and other soils.
- E-Kleen SR 102-E is a non-silicated liquid soak cleaner that emulsifies soils and oils.
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 (optional)
If the pieces to be blackened have scale or rust on the surface, it must be removed following cleaning and rinsing (Steps 1 and 2) in a 50% by volume muriatic acid solution or in an 8oz. to 2lb. per gallon solution of E-Pik 215 dry acid salts. Rinse thoroughly with water following descaling and derusting.
Following the pickle step, thoroughly rinse the parts with water before blackening.
Immerse the steel part in a boiling (285–290º F) solution of Ultra-Blak 400-L until a uniform black color is achieved. Immerse the part for 5–20 minutes, depending on the size/mass of part, depth of black desired, and the metal's surface condition. See the technical data sheet for specifics on time, temperature, and solution makeup.
If Ultra-Blak 400-L isn't quite what you’re looking for, consider these similar products:
- Insta-Blak 333 is a liquid immersion blackening solution that results in a smooth, no-smut satin black finish on tools and architectural surfaces. It's used at a room temperature.
- 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.
Rinse in cold, overflowing tap water for 30–60 seconds to remove residual blackening solution and ensure sealant will not be contaminated. Transfer the metal parts from the blackening solution to the cold-water rinse as quickly as possible to avoid discoloration.
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.
See the rust preventative and sealing comparison chart to find the best E-Tec solution for your needs.
Recommended Sealing Products:
- E-Tec 501 produces an oily finish and helps inhibit rust and corrosion.
- 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-Tec 520 is used to deposit a corrosion-inhibiting, hard, clear, glossy, and dry finish.