Ductile Iron Grooved Coupling: Ductile Iron Couplings, Grooved End, Material ASTM A536, Grade 65-45-12, EPDM Gasket, Epoxy, Orange Surface. Keywords: Ductile Iron Grooved Coupling. Name: Grooved Coupling. Material: Ductile Iron, ASTM A536, Grade 65-45-12. Gasket: EPDM. Bolts & Nuts: ISO 898-I Class 8.8. Surface Treatment:Epoxy - RAL3000 & Painted - RAL3000 & Painting - ORANGE.