Over the years, a strong down-gauging trend has been observed for the various automotive radiator materials answering the continuing pressure for weight and cost reduction. Downgauging, on the other hand, requires an improvement of the corrosion resistance of both tube and fin stock alloys. Air-side corrosion resistance has been ensured by the application of suitable pre-treatment and corrosion protection systems. But with the introduction of highly corrosion resistant (“long-life”) alloys for tube stock products with optimized compositions e.g. based on EN AW-3110, it has been possible to eliminate these costly and sometimes environmentally hazardous surface treatments. (Additional protection of the external surface of the tube can be achieved by using fin stock alloys that preferentially corrode in contact with the tube alloy (i.e. the fins act as sacrificial anodes). For this reason, the fin alloy must be more electronegative than the tube alloy. The preferred option for achieving a fin that protects the tube against corrosion is the addition of zinc, typically in the range of 1.0 to 2.5 wt. % Zn. However, in vacuum brazing, the low vapour pressure of Zn means that a significant proportion evaporates and the remaining Zn level in the fin is difficult to control. Thus for vacuum brazed radiators, the use of alloying elements with a high vapour pressure like tin or indium is sometimes preferred to lower the electrochemical potential. The low melting point Al-Si alloys which are used to clad the tube stock are – in the brazed condition – already slightly electronegative to most of the Al-Mn based tube alloys, i.e. the addition of Zn to the clad alloy is often not necessary)
Alloys available at HE Tubing:
On customer specific request, we do have following Alloys available:
EN AW-3102 modified, EN AW 3003 modified, EN AW-3026 en C47D (see table below).