Why does stainless steel sink turn black?

There are several possible reasons why your stainless steel sink may turn black over time. Some of them are:

Exposure to high heat, such as from the stovetop or dishwasher, can cause the metal to oxidize and form a black oxide layer on the surface.
Contact with acidic substances, such as vinegar, lemon juice, or cleaning products, can erode the protective chromium layer and expose the iron underneath, which can rust and stain.
Scratches or abrasions on the sink can trap moisture and dirt, which can promote bacterial growth and mold formation, resulting in black spots or patches.

To prevent or remove the black stains from your stainless steel sink, you can try the following methods:

Use a mild abrasive cleaner, such as baking soda or Bar Keepers Friend, and a soft sponge to gently scrub the affected areas. Follow the grain of the steel and rinse well with water.
Apply a solution of bleach and water to kill any mold or bacteria that may be present. Then, use vinegar to neutralize the bleach and remove any residue. Rinse and dry thoroughly.
Polish the sink with a stainless steel cleaner or a paste of olive oil and flour. This can help restore the shine and create a protective barrier against future stains.

I hope this helps you keep your stainless steel sink clean and shiny.

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