Devcon (Danvers, MA) has two metal-filled epoxies that can be used to maintain compressor coils. The aluminum-filled hvac repair putty (Special F) bonds to metals, ceramics, wood, concrete, or glass and can be used to make nonrusting repairs to copper compressor coils and aluminum castings. The aluminum putty (F) is designed for repairs to aluminum castings and machinery in addition to hvac applications.