swingtop quality differences

[kapbrew13]

I noticed the metal swingtop from the midwestsupplies.com corrode when I soak it in oxyclean and starsan. The metal becomes white-ish and starts flaking off. However I don't experience this on the real grolsch bottles.
Anyone else experience this?

 

[Vongo]

I take my swing tops off if i need to give them a good soak.