Pre-coated tubes for brazed heat exchanger - experience with Zn containing fluxes

摘要

Since the introduction of HYBRAZ coated products, there has been a significant drive towards the use HYBRAZ coated Multi Port Extruded (MPE) tubes. NOCOLOK Silflux (NOCOLOK Flux and Si particles) coated MPE tubes has been well established as a means of brazing MPE tubes with unclad fin. At the same time there is a significant interest in using reactive Zn flux on MPE tubes. The HYBRAZ coated products containing reactive Zn flux will then provide flux for brazing and a Zn diffusion gradient into the tube for corrosion protection. The current work will reflect some experience in the application of NOCOLOK Zn containing coatings. Beside various benefits in the application of pre-coated tubes the industry is struggling with the organic content within the coating. In a second part this paper will discuss the main process parameter with respect to binder amount, removal of the binder, interaction of the binder with particles and decomposition products.