The Blackening Process: Insta-Blak SS-370
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 prior to beginning the blackening process.
Recommended Cleaning Products:
- E-Kleen SR 148-E is a low-caustic formula that's ideal for removing a wide range of oils and soils.
- E-Kleen SR 102-E is a high-caustic formula that removes difficult-to-clean metal-working fluids.
- E-Kleen 163 works well in hand-blackening applications at room temperature. It contains no caustic and is not hazardous.
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. Blacken
Experimentation will be required to determine the optimum concentration and length of immersion. For 300 series alloys, begin with a 50% by volume solution, and for 400 series alloys, begin with a 25–33% by volume solution. Difficult-to-blacken surfaces may require the use of Insta-Blak SS-370 at full strength.
Immersion times will vary from 2–5 minutes. Very passive surfaces may require further activation to initiate the blackening reaction, which can be achieved by having plain steel in contact with the stainless steel parts while immersed in the blackening solution. Steel hooks, wire, or suspension racks are often used to achieve extra oxidation.
If Insta-Blak SS-370 isn't quite what you’re looking for, consider these similar products:
- Ultra-Blak 407 is a hot-temperature process that makes it easier to get a dark-black finish on difficult-to-blacken parts.
4. Rinse
Rinse in cold, overflowing tap water for 30–60 seconds to remove residual blackening solution and ensure sealant will not be contaminated.
5. 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-Tec 504 is a solvent-based, dry-to-touch oil formula.
- E-Tec 515 is a water-soluble oil that contains no VOCs. It's the most economical method for achieving corrosion protection.
- E-Tec 522 is a water-based satin wax for lubrication properties. It provides a dry-to-touch finish.
