... a steel surface, you can use either a North or South pole magnet. They are equally as strong.If you want to ... cardboard folder, you need to use a North pole and a South pole magnet so that they attract each other (otherwise they ... to 53MGOe with wonderful coercive force6. For most applications, coating or plating is recommended.7. Coatings: Ni, Zn, gold, copper, epoxy ...