why do shinny aluminum pie plates turn dull and dark grey in a dishwasher.

Question

Even on low heat. What exactly is the reaction?

In: 6

Answer 1

The reaction is aluminum plus oxygen (from the air) making aluminum oxide, which is dark grey or black. It’s basically “rusting” (normal rust is iron plus oxygen making iron oxide). The warmth and abrasion in the dishwasher makes the oxidation of aluminum go faster than it would normally.