- FAQ
- Black Oxide
Black Oxide
What is black oxide?
Black oxide is a blend of caustic, oxidizers, and additives that is used on ferrous metals. There are three types of metal blackening: hot, mid, and room temperature blackening. EPi was the first company to offer all three processes.
Hot black oxide (285 F°) is a conventional hot process which produces a true black oxide iron magnetite (Fe3O4) finish. It is a premium-grade salt mixture which will blacken a wider range of steel alloys than any other process on the market.
Mid-temperature black oxide (225–245 F°) is the latest development in blackening processes, producing a true black oxide iron magnetite (Fe3O4) finish. It produces no caustic boiling fumes and provides a safer working environment.
Room-temperature blackening (65–85° F) is the preferred metal-blackening process for safe and convenient in-house blackening. It is an excellent non-bleed black finish for powdered metal and cast iron. It produces super deep blackness and corrosion resistance equal to hot oxide blackeners.
It is important to note this is not a true black oxide process; however, it may be referred to as room-temperature black oxide. Room-temperature blackening processes are autocatalytic reactions of a black selenium-copper compound that deposits on ferrous parts through an immersion process.
What makes EPI’s black oxide and metal-blackening processes better?
Insta-Blak processes do not produce smutty rub-offs like other room-temperature products. Our Ultra-Blak products are premium-grade black oxide, and Kool-Blak does not produce a smutty rub off like other mid-temperature processes. They are easy-to-use with wide windows of operation.
What are the advantages of black oxide and metal blackening?
Ultra-Blak:
- Produces true black oxide finish Fe3O4 magnetite finish
- Abrasion resistance
- Corrosion protection
- Meets military spec MIL-DTL-13924D and AMS 2485H
- Blackens faster than other hot black oxides
- Less sludge generation than other hot black oxides, which means lower gas bills
- Capital costs less than $10,000–15,000 for turnkey operations
- Energy savings
- No CO2 emissions or green house gases
- 1–5 minute process time for blackening
- Powder metal does not bleed-out white salts like hot black oxide
- Cast iron and steel castings do not turn red
- No ventilation costs
- Provides corrosion resistance
- Dimensional stability thickness 5–10 millionths of an inch
- Can be painted over
- Anti-galling properties
- Aesthetic appeal
What can black oxide be used for?
Black oxide can be used on a wide variety of metals. Examples of specific products that can be blackened with black oxide are listed below.
- Locks
- Automobile and motorcycle parts
- Machine parts
- Power tools
- Hardware and electornic hardware
- Architectural applications
- Furniture
- Ironware
- Exercise equipment
- Large metal sheets
- Gears
- Hydraulic and pneumatic components
- Lawn and garden equipment
- Candle holders
- Fasteners
- Storefronts or displays
Who uses black oxide?
Large companies such as lock manufacturers or auto manufacturers use black oxide on a large-scale basis to blacken metal parts. Black oxide can also be used by the home hobbyist who would prefer to blacken just a few items. Below are some of the major industries that use black oxide coating.
- Ammunition manufacturers
- Appliance industry
- Architectural industry
- Auto industry
- Camping and hunting
- Collars/coupling industry
- Construction equipment industry
- Fastener industry
- Firearms
- Hardware industry
- Metal stampers
- Military components
- Oilfield Industry
- Power hand tool manufacturers
- Recreational vehicle industry
- Tool & die industry
- Tube cutters/fabricators
How is black oxide applied?
Hot- and mid-temperature black oxide is applied through a seven-step process.
- Clean and degrease metal parts
- Rinse metal parts
- Hydrochloric acid
- Rinse metal parts
- Blacken parts in boiling solution (hot: approximately 285 F°, mid: no boiling, 225–245 F°)
- Rinse metal parts
- Seal and finish
- Clean and degrease metal parts
- Rinse metal parts
- Blacken metal parts 1–5 minutes at 65–85 F°
- Rinse metal parts
- Seal and finish
What types of metal can you blacken with hot or room-temperature black oxide ?
- Steel
- Stainless steel
- Cast iron
- Copper
- Brass
- Cadmium
- Zinc
- Nickel
- Electroless nickel
How to prevent blackened parts from getting rusty?
Customers reach out to us asking how to prevent their freshly blackened parts from rusting. EPi recommends:
Use running water to rinse the parts for 1-2 minutes;
Do not dry the parts between prepping, cleaning, and blackening;
Do not use compressed air to dry the parts as it contains water droplets;
Apply E-Tec (see instructions) sealer to extend the life of the finish and protect the surface.
One of our customers shared their experience/process with us. After analyzing their process, we concluded that using compressed air for drying the parts may lead to rusting. Below is their process:
- Using a cleaning solution on the parts
- Rinse in Distilled water
- Soak in Black Oxide Concentrate, currently mixing 8 to 1 with Distilled Water
- Rinse in Distilled Water
- Soak in oil
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