On 21 Nov, 17:30, devonsteve wrote:
Can anyone tell me how to clean blackened stainless steel pans ,

Barkeeper's Friend, which is oxalic acid as a white powder. Same stuff
as rhubarb, but easier to work with. If you are using rhubarb though,
leaves are better than stems and remember that it's quite toxic stuff.

Otherwise scrubbing with such things as a Garryflex block (abrasive
grit in rubber). Then for kitchen use, passivate again afterwards to
avoid future staining. Use 15% citric acid solution (homebrew shop).