Manganese sulfate and the colored stainless steel

No matter mirror stainless steel or frosted smooth stainless steel, it is always a piece of silvery white that leaves a frosty feeling to us. If added manganese sulfate, the stainless steel may show some color.

The principle of colorful stainless steel: The color is caused by a colorless transparent density oxide film on the surface. When lights shine on the film, its reflected lights interfere in the refraction lights that come from the film. Then the color happens. The thickness of the oxide film is commonly 200 ~ 400 nm. For thinner oxide film, the stainless shows blue or brown; For medium thickness of oxide film, it shows golden yellow or red; For thicker oxidation film, it shows green or even black.
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The coloring process of colored stainless steel: generally divided into three stages: oxidation film (also known as coloring processing), electrolytic curing, and closed processing.

To color the stainless steel black is to apply the solution consist of manganese sulfate, potassium nitrate, potassium bichromate, ammonium sulfate, sulfuric acid under the about 98 ℃ temperature for 5 ~ 15 min. It’s a chemical blacking process that manganese sulfate plays the role of black agent.