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Question:
When I was doing dishes, tonight, I noticed many colors on the bottom of a stainless steel pot. What causes them colors?



Replies:
Thanks for your question. I suspect the rainbow like colors you saw on the bottom of the pot are due to various degrees of oxidation of the stainless steel. Metal, when exposed to heat and moisture in the presence of oxygen (one of the gas components of the air we breathe) will cause or rather will oxidize. This is comparable to rust forming on a piece of metal left outdoors. The rust (a thicker oxide) or the rainbow colors (an oxide which is very very thin) can be easily removed by scouring the bottom of the pot. Another interesting way to remove it would be by using a common household material like a few drops of either vinegar or lemon juice. You can ask your parents to help you with this. If you place a drop or two of the vinegar or lemon juice on the rainbow color, you will see it vanish and the shiny metal color will reappear. This happens because the oxide which had formed is dissolved away, leaving the original metal.

In my job making integrated circuits we use the oxidation of metal sorry metal (silicon) to form various mask patterns to create levels of circuitry to make the computer "chips". You can read about computer chips in your school library. Please let me know if this information helps, or if I can make it any clearer for you.

rickru



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