Guys I need to find out what this is- it's also on my wooden bed racks
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If you run your finger over those spots, do you feel and pitting? – Fizz Sep 7 '17 at 17:31
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Also, are those bars steel or aluminium? I'm inclined to think the former, but it's hard to tell with the camera flash. (You can determine using a magnet.) – Fizz Sep 7 '17 at 17:51
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Hello, and welcome to Stack Exchange. We're closing the other question you created on this (as a different user); please don't submit duplicates. – Daniel Griscom Sep 10 '17 at 18:01
The pictures seem to be showing corrosion of aluminum. The finish on the aluminum, whether that be a clear anodize or other lacquer or enamel coating, has failed in spots and is allowing aluminum oxide to form. As you can guess aluminum oxide is white in color.
answered Sep 7 '17 at 2:06
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Aluminium oxide (=alumina) is not found in pure form on the surface of bars like this. It will be contaminated with iron oxide and thus be grey not white. Making pure (white fused alumina) WFA is done only for abrasives and is expensive (requires a Bayer process to remove the iron.) Try rubbing some aluminium and see if your get white powder... it will be grey instead. – Fizz Sep 7 '17 at 17:42
The white outer circles appears to me to be white rust, which is a term for corroded zinc; zinc is the protective layer of galvanized steel. The inner darker disks... probably indicate exposed steel (no longer covered by zinc), possibly slightly corroded as well.
