All Innomag  pump internals are molded with thick layer of mechanically tough, chemically inert ETFE or optional PFA fluoropolymer.  These polymers are designed for high corrosion resistance and strength over a wide temperature range. However, essentially all plastics are semi-permeable.  This means that they allow small atoms, ions or molecules present in the pumped fluid to pass between their molecules like a very fine sieve.  Many of these materials are very corrosive.  This normally doesn’t affect the plastic but can allow the corrosive products to attack the underlying materials.  By far the most vulnerable parts of any mag-drive pump are the magnets.  Innomag pumps are made using neodymium-iron-boron magnets which are the strongest available but not very corrosion resistant.