So, we thoughtlessly put a Bialetti stove-top espresso pot through the dishwasher. Didn't even stop to think it mightn't be dishwasher safe. Now it has gone dull, and inside the main coffee chamber has a coating of black dust which comes off on your hand.
In hindsight I discovered Bialetti pots are anodised aluminium. I know a little about this - they are covered in a thin form of very hard, insoluble oxide formed by passing electricity through aluminium. This is not the normal way that aluminium oxidises ('rusts') and if you scratch anodises aluminium the shiny surface will oxidise with a much less hard-wearing substance.
So I believe the dishwasher has either dissolved or abraded away the entire anodised coating, and the black dust is a different form of aluminium oxide. Bummer.
The part I'm unclear of is if I remove this black layer, will it just keep happening? Is the black oxide powder the natural oxide aluminium produces, or something specific to the conditions inside the dishwasher? Online I see people recommending polish, vinegar, and heat-treating but they aren't very scientific and knowing about anodisation I'm unconvinced. Is there a way, short of re-anodising, I can get a stable coating? It doesn't have to be shiny, just something that isn't going to powder everywhere no matter how much I wash it.
Answers from people with actual science knowledge preferred
In hindsight I discovered Bialetti pots are anodised aluminium. I know a little about this - they are covered in a thin form of very hard, insoluble oxide formed by passing electricity through aluminium. This is not the normal way that aluminium oxidises ('rusts') and if you scratch anodises aluminium the shiny surface will oxidise with a much less hard-wearing substance.
So I believe the dishwasher has either dissolved or abraded away the entire anodised coating, and the black dust is a different form of aluminium oxide. Bummer.
The part I'm unclear of is if I remove this black layer, will it just keep happening? Is the black oxide powder the natural oxide aluminium produces, or something specific to the conditions inside the dishwasher? Online I see people recommending polish, vinegar, and heat-treating but they aren't very scientific and knowing about anodisation I'm unconvinced. Is there a way, short of re-anodising, I can get a stable coating? It doesn't have to be shiny, just something that isn't going to powder everywhere no matter how much I wash it.
Answers from people with actual science knowledge preferred
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