PG classics
This is a current thread so I’m spouting off here. Anytime you buy diecast pot metal parts, you take the chance of inferior base metal quality. Its called pot metal for a reason, its all scrap tossed into the pot, aluminum,zinc,magnesium and whatever. You will also find trace of heavy metals,lead,cadmium ect. There is also dirt and that is what causes blistering. Eventually it all blisters. Restoration is expensive. Crome platers mostly refuse to crome stuff they don’t repair or have a relationship with the restorer.
There is nothing you can do to stop blistering and pitting. Waxing,cleaning, controlled environment don’t matter, its in the casting material.