Corrosion resistant metal tube and process for making the same

摘要

A corrosion resistant multi-layer tube (10) comprises a metal tube (12); a zinc layer (14) bonded to the metal tube outer surface (13); a surface treatment layer (16) bonded to the zinc layer (14); a priming layer (17); a first polymeric layer (18) bonded to the priming layer; a second polymeric layer (22) bonded to the first polymeric layer (18). A process for manufacturing the tube comprises the step of extruding multiple layers of a melt-processible thermoplastic to a pretreated metal tube having an external surface with at least a zinc based coating, a sealant coating on top of the zinc based coating, and a primer coating on top of the sealant coating. The primer coating (17) is preferably applied by an airless spray system in a closed atmosphere, wherein substantially no volatile organic compounds escape into the atmosphere. The polymeric layer(s) remain adhered to the metal tube, even when exposed for prolonged periods to aggressively corrosive environments.