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    Stainless steel can turn black? What is the cause?

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    Stainless steel is a compound widely used in everyday life and is safe for users. Also known as corrosion-resistant steel or stainless steel, it contains more than 10.5% Chromium. The chromium in stainless steel reacts with oxygen to form a passive film of Chromium oxide.

    This compound envelops the steel material, preventing contact with the external environment. If stainless steel is scratched, the Chromium oxide film quickly forms a thin layer that heals the scratches and prevents corrosion.

    However, in low oxygen environments with high chloride content, Chromium oxide is less effective, failing to protect the material. For instance, in a salty water environment, the passive film lacks the oxygen needed to form a layer of Chromium oxide, which can lead to the steel turning black.

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    What causes stainless steel to turn black?

    Stainless steel turns black due to two main reasons:

    Chemical corrosion is the oxidation-reduction process of the metal, reacting directly with oxygen, usually in water and air environments.
    Electrochemical corrosion is the destructive process of metal, a reaction of the metal with an electrolyte solution.
    To limit this condition, stainless steel should not be exposed to the environment to avoid oxidation. Additionally, protective coating or preservation grease can be applied.

    Notes on using stainless steel

    Do not apply chemicals to the surface of stainless steel

    To extend the lifespan of stainless steel, customers should note the following when using stainless steel:

    • Choose the appropriate type of stainless steel: Based on the intended use and the installation environment, customers should select the suitable type of steel.
    • Do not apply chemicals to the surface of stainless steel: To clean stainless steel, customers should choose the appropriate cleaning solution, avoiding those with harsh chemicals that can damage the metal.
    • Store stainless steel correctly: Customers should store stainless steel in dry, cool places, avoiding damp, moldy areas that are prone to corrosion.
    • Use correctly: Each type of stainless steel comes with its own usage instructions. Customers should follow these guidelines to avoid reducing its lifespan.
      Inox Viet  is always ready to advise on products suitable for our customers’ needs.