Surface treatment using nickel is often desirable. Depending on the magnet material, different processes are utilized for nickel-plating the magnet. We will look at each basic material and cover the appropriate processes offered.
Non-metallic materials cannot be nickel-plated. Bonded Neodymium Iron Boron, Bonded Samarium Cobalt, Ceramics and Bonded Ceramics fall under this category.
These are Alnicos, Samarium Cobalt, and Neodymium Iron Boron. They can be nickel-plated. Different processes are utilized depending on the material being plated and the application. Below, we will look at the purpose and solution for each.
Generally it is not necessary to plate Alnicos; however, when plated, Alnicos are typically nickel plated for cosmetic or engineering reasons.
Samarium Cobalt is not prone to oxidation; however, occasionally “staining” may be visible. This is typically due to minor iron impurities that occur as part of the process and does not indicate that the material is deteriorating. This oxidation typically will cease after the free Fe impurities are oxidized and will not affect the performance of the magnet. Nickel plating is requested for reasons other than cosmetic. Generally the Military Specification is called out, but the Federal Specification may also be used. X-Ray tests are sometimes required to determine the applied thickness of the plating. See testing and certification for more information.
When Samarium Cobalt magnets need to be nickel plated, one of the following process specifications should be used:
Process K1303 – This process is similar to Electroless Nickel Plating with MIL-C-26074 Class 1 Grade A, except magnets are pre-treated to improve adhesion.
Process K1304 – This process is the same as K1303, except within a 4 hour period of plating, parts are baked for 3 hours to provide a Hydrogen Embrittlement relief bake. This is not considered a heat treatment. This process should only be utilized if the magnets will be used in a hydrogen rich atmosphere.
Neodymium Iron Boron is prone to oxidation; however, magnets provided by MCE have oxidation rates far below industry standards. Nickel-plating is generally required to ensure longevity of the magnet, cleanliness, and to prevent oxidation. When nickel-plating Neodymium magnets, one still needs to be aware that the process must be very closely controlled. The process of nickel-plating itself can be destructive to the magnet if care is not taken, and while the magnet may look good visually after the application of plating, rapid oxidation may be taking place under the coating, causing a reaction that may only be evident after a few months.
MCE has developed and employs its own proprietary processes, from pre-treating to handling, in-process handling, etching, and subsequent surface treatment in the application of nickel. The process is electrolytic Nickel Plating. This is called Process K1055.