there are products for kitchen use by the name calcite or phosphate removers, use that instead. u need to dip the core for around 24 hours and u wil have removal of water based calcites and no harm to metal.and there is another solution which can be made with synthetic vinegar and water, 1:2. dip your core in it for 4 to 5 hours or more if needed it will give excellent results against calcites and phosphates.
