Black Oxide Coating at ECO Finishing
ECO Finishing provides Black Oxide coating services in Minneapolis that are compliant with MIL-DTL-
3924. With over 60,000 sq ft of clean, well lit space, ECO Finishing has a streamlined process that
complies with all EPA regulations regarding safety and waste treatment.
The Black Oxide coating process was developed in the early 1900's and the chemical process has
changed little since. Black Oxide is a chemical conversion coating process, and as such does not change
the dimensional properties of the coated part. When a part is coated with Black Oxide, the chemical
conversion process converts the iron to the naturally occurring black iron oxide compound called
magnetite. The coating becomes an integral part of the base metal and does not chip, peel, crack or rub
off. Further, the coating is resistant to bending and flexing of the base metal. Black Oxide has limited
Black Oxide can be used to coat mild steel, stainless steel, brass, bronze, copper, zinc and powdered
metals. There are four classes of Black Oxide coating, including:
Class 1,2 and 3 need to pass an "oxalic acid spot test" prior to the application of a preservative.
All classes need to pass the "smut test" after coating and before application of corrosion
- Class 1 Alkaline oxidizing process for wrought, cast and malleable irons, plain carbon and
low alloy steel
- Class 2 Alkaline chromate oxidizing process for certain corrosion resistant steel alloys which
tempered to 900 degrees F or higher. Coating shalled be formed from a boiling alkaline
chromate oxidizing solution.
- Class 3 Fused salt oxidizing process for corrosion resistant steel alloys which are tempered
900 degrees F or higher. After immersion parts are withdrawn, cooled for eight to ten
minutes and rinsed in hot water.
- Class 4 Alkaline oxidizing process for other corrosion resistant steel alloys. Salt spray test
ASTM-B117 prior to application of a preservative.
ECO Finishing provides Black Oxide services to a wide range of industries including automotive,
aerospace, medical, military and manufacturers of industrial and consumer products. Our Black Oxide
coating tank is 5' x 3' x 3' allowing us to coat both large and small parts.
Quality is at the heart of ECO Finishing. Each job is carefully monitored from its arrival through the
entire plating process. Inspection of plated parts is enhanced by more than 100 foot candles of light
throughout the entire plant. Zinc plated thickness measurements are verified with X-ray fluorescence
and our quality system conforms to military specifications as outlined in MIL-Q-45208. ECO uses
Statistical Process Control (SPC) to assure that our product meets exacting industry standards.
ECO Finishing has the fastest lead time of any metal finishing company in Minnesota. We can process
within hours, within a day or on your schedule. Our average turn time is two to three days. The goal is
to support our customers as they grow their business by beating their competition.
At ECO Finishing, we believe that our job is to make your life easier! We specialize in Just in Time
(JIT) deliveries and fast turnaround orders. We are known by our customers for our commitment and
dedication to quality. ECO has the history, experience and professionalism to be sure to make your job
easier. Contact ECO Finishing today for Black Oxide at (763) 574-1000.