(aka Black Penetrate, Black Magic, Black N, and Gun Bluing)
Black Oxidizing is an effective metal finishing process with which a Black Oxide (blackening) conversion coating is applied to parts to add corrosion resistance, improve appearance, minimize light reflection, and serve as a base for other coatings.
Although it’s possible to apply black oxidizing at a range of temperatures, the preferred and most widely accepted is the Hot Black Oxide application, which meets military and automotive certification specifications.
Basically, the black oxidizing process converts the surface of the material into magnetite (Fe3
) as the parts are dipped into hot baths of sodium hydroxide, nitrates, and nitrites at 286o
C). Water must be periodically added with proper controls.
Once the black oxidizing process is complete, it’s important to apply a final finish or sealant (also known as an after-finish), which is usually oil, wax, or lacquer. This is what strengthens the bond to prevent corrosion. The choice for the right sealant depends on factors such as the environment in which the black oxidized parts will be used/stored, the desired appearance, and the length of time protection is needed.
Black Oxidizing for Stainless Steel
Applying Hot Black Oxide for stainless steel involves using a mix of caustic, oxidizing, and sulfur salts. Generally, it’s applied to 300 and 400 series, and the precipitation hardened 17-4 PH stainless steel alloys. It can be used on cast iron and mild low-carbon steel. This process complies with military specification MIL-DTL-13924D Class 4 and provides abrasion resistance.
Black Oxide Shop in Chicago, IL - Pro-Tec Metal Finishing
Pro-Tec Metal's Process Line of hot black oxide is used to produce a true durable black oxide conversion coating on steel, stainless steel and copper alloys. From the black oxide process, these essentially dimensionless coatings create very decorative, highly durable black finishes that leave an absorbing oxide layer for oils and waxes that will provide for enhanced corrosion protection.
RACK & BARREL OPERATIONS
Features and Benefits
No dimensional change
Does not affect conductivity
Increased corrosion resistance
No hydrogen embrittlement
Reduced light glare
Provides anti-galling properties
Base for organic coatings