An important challenge during design and brazing is to optimise the combination of the different materials fin, Micro Port Extrusion (MPE) and header used in the heat exchanger.
Over the years, a strong down-gauging trend has been observed for the various automotive heat exchanger materials, answering the continuing pressure for weight and cost reduction. Downgauging, on the other hand, requires an improvement of the corrosion resistance of both the micro port extrusion and fin stock alloys. Air-side corrosion resistance has been ensured by the application of suitable pre-treatment and corrosion protection systems.
NEXCOR™ Long Life Alloys (LLA’s): superior extruded aluminium MPE’s and Round Tubing for Automotive and HVAC/R heat exchanger applications.
- Most highly corrosion resistant bare aluminium alloys – requiring no zinc arc spray or chromate coating to withstand intense environmentally corrosive conditions
- Extends high efficiency life cycle of heat exchangers – no tube-to-fin separation to degrade performance
- Durable and promotes a higher post-braze strength for a more stable microstructure
- Substantial cost saving over copper (HVAC/R applications) with a weight reduction of 40-50%.
With the introduction of highly corrosion resistant LLA’s for the MPE with optimized compositions like the EN AW-3110 NEXCOR™ alloy, it has been possible to eliminate these costly and sometimes environmentally hazardous surface treatments. Additional protection of the external surface of the MPE can be achieved by using fin material alloys that preferentially corrode in contact with the MPE alloy (i.e. the fins act as sacrificial anodes). For this reason, the fin alloy must be more electronegative than the MPE alloy. The low melting point Al-Si alloys which are used to clad the MPE are – in the brazed condition – already slightly electronegative to most of the Al-Mn based MPE alloys, i.e. the addition of Zn to the clad alloy is often not necessary.
Alloys available at HE Tubing: