Aluminum or magnesium does not “rust” like iron or some other metals when it oxidizes. These two metals havee a coating of oxide that blocks continued oxidation after it gets to a certain thickness. This is why they can look good for so long especially when exposed to outdoor conditions.
So, you would think that these metals should work well in washing machines.
Well, it is if you only use detergent and softener in the machine. These products are buffered to be in the 8.0 - 9.0 pH range. The machine is designed for these chemicals.
Apparently, if you go outside the normal operating range of the washer too far the aluminum of the spider flange will corrode. Then it will crack.