Self-Healing Corrosion Protection Coatings for Nd-Fe-B Magnets
A neodymium magnet (Nd—Fe—B) is protected by a self-healing, corrosion-resistant coating of (a) a sacrificial metal layer; (b) optionally, a metal pretreatment layer on the sacrificial metal layer; and (c) an electrocoat coating layer.
1 . A method of protecting a neodymium magnet, comprising
(a) applying a sacrificial metal layer;
(b) optionally, applying a metal pretreatment layer onto the sacrificial metal layer; and
(c) applying an electrocoat coating layer.
2 . A method according to claim 1 , wherein the sacrificial metal layer comprises a member selected from the group consisting of:
aluminum, zinc, magnesium,
combinations thereof, and
aluminum, zinc, and magnesium alloys.
3 . A method according to claim 2 , wherein the sacrificial metal layer comprises a member selected from the group consisting of:
aluminum, combinations of aluminum with one or both of zinc and magnesium, and aluminum alloys.
4 . A method according to claim 1 , further comprising curing or crosslinking the applied electrocoat coating layer.
5 . A method according to claim 4 , wherein the electrocoat coating layer is applied from a composition comprising an acid-solubilized reaction product of polyepoxide and primary or secondary amine and a blocked polyisocyanate curing agent.
6 . A method according to claim 1 , wherein the metal pretreatment layer is applied onto the sacrificial metal layer and the metal pretreatment layer comprises a phosphate.
7 . A method according to claim 1 , wherein the electrocoat coating layer is applied directly to the sacrificial metal layer.
8 . A neodymium magnet, comprising a coating comprising:
(a) a sacrificial metal layer;
(b) optionally, a metal pretreatment layer on the sacrificial metal layer; and
(c) an electrocoat coating layer.
9 . A neodymium magnet according to claim 8 , wherein the sacrificial metal layer comprises a member selected from the group consisting of:
aluminum, zinc, magnesium,
combinations thereof, and
aluminum, zinc, and magnesium alloys.
10 . A neodymium magnet according to claim 9 , wherein the sacrificial metal layer comprises a member selected from the group consisting of:
aluminum, combinations of aluminum with one or both of zinc and magnesium, and aluminum alloys.
11 . A neodymium magnet according to claim 8 , further comprising curing or crosslinking the applied electrocoat coating layer.
12 . A neodymium magnet according to claim 11 , wherein the electrocoat coating layer is a crosslinked reaction product of a primary or secondary amine-functional polyepoxide and a polyisocyanate curing agent.
13 . A neodymium magnet according to claim 8 , comprising a metal pretreatment layer comprising a phosphate.
14 . A neodymium magnet according to claim 8 , wherein the electrocoat coating layer is directly on the sacrificial metal layer.