High corrosion resistance neodymium magnets are simply neo magnets with better corrosion resistance then regular neo magnets. NdFeB magnets are very corrosive even under regular environment (room temperature and low humidity). Therefore, these magnets are produced in vacuum conditions and are coated with a variety of coatings to keep them from corrosion.
High corrosion resistance Neodymium magnets are produced in a special process. Therefore making them more resistance to corrosion. These magnets have significantly better results in salt spray tests, for example. The magnetic characteristic of these magnets are quite similar to regular NdFeB magnets. Though coating is not a necessity but a recommendation. Regular neo magnets with coating always are in risk of corrosion. Small impacts or wrong assembly can probably damage the coating. When the coating is being damaged and corrosion starts, the magnets will start to lose some of their magnetic properties. That is a good reason to use high corrosion resistance neodymium magnets is certain magnetic applications. Due to its higher corrosion resistance, these types of magnets became highly popular in high end military and space magnetic application.