What is the reason that black dye does not turn black?

【Troubleshooting】Black dye has turned brown or faded. We will explain the causes and countermeasures.

Black dyeing treatment is a surface treatment that reacts iron products in a high-temperature alkaline solution to form a black oxide film known as magnetite (Fe3O4). It has rust prevention effects and benefits such as anti-reflection and aesthetic enhancement. Black dyeing of general steel materials (raw materials) usually results in a deep black finish. However, for some materials, such as cast iron or those that have been hardened, as well as alloy steels that contain high amounts of chromium or other nickel, the result may be a reddish-black or a light gray instead of black. Additionally, wire-cut surfaces may appear brownish, resembling rust. The following causes can be considered: - Residual oil (insufficient degreasing) - Inadequate removal of the oxide film - High content of components other than iron in the material, leading to uneven reactions - Rough surface of the material, resulting in uneven reactions The following countermeasures can be taken: - Strengthening degreasing and cleaning - Removal of the oxide film through acid washing - Removal of thick oxide films and uniformity of surface roughness through sandblasting - Selection of black dyeing solutions suitable for alloy steels (such as SUS) Based on years of experience, our company selects black dyeing processes tailored to the material and processing history. If you have any concerns about black dyeing, please feel free to consult us.

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