I have been working on designing a submersible platform, held underwater by electromagnets. When the platform is submerged is exerts about 3 kg of bouyancy. When power is cut to four electromagnets at the base of the platform, the platform rises to the surface. Functionally it works well, but I am having trouble preventing corrosion of the electromagnets. I experimented with some magnets made of 400 Series Magnetic Stainless Steel, but passivation is not perfect and they still show signs of rust. I have tried nickel coating, painting and plastic coating but the nickel corrodes, the paint seems to crack around the edges of the magnet, and the plastic adds too much gap for the magnets to work. Does anyone have any suggestions or previous experience with submerging electrical components?