These are the new magnets, they are Ferrite, the same material most impellers are made from and will not corrode. They don't need waterproofing, the old magnets were neodymium and had iron plates, these required waterproofing. Neodymium has gone up in price over 500% and to keep costs down we switched but the old neodymium for up to 3/4" contained 2 tiny magnets, not much bigger than an N cell battery, to get to the roughly 5/8" we have from the Ferrite the entire magnet holder is full of Ferrite. The only way these will get any corrosion is if iron particles stick to them, the attracted iron will corrode but the ferrite itself will not.