The alloy composition of HyLife™ Solar enhances the life expectancy of the aluminium tubes in two ways. This can be seen in the images below, which are the results of a SWAAT test. The SWAAT test is an accelerated salt spray test and a common corrosion test in the automotive industry.

EN 3103 alloy after 8 days in SWAAT (0.4 mm wall)

Long life alloy after 41 days in SWAAT (0.4 mm wall)

Firstly, any external corrosion attacks, are in character very different from the traditional ‘pitting corrosion’ of aluminium. The corrosion is spread laterally over a larger area and isn’t focused in depth.

Secondly, the corrosion resistance is significantly increased. The top image shows the result of a 3103 alloy after only 8 days, to be compared to the bottom image which is the result of HyLife™ Solar after 41 days. This simulates several years of harsh outdoor conditions.

Hydro recommends using HyLife™ Solar for solar thermal systems. With HyLife™ Solar tubes in a correctly designed solar thermal system, there is no risk of corrosion. Designing a system correclty, means that the system needs to be a closed system (hermetically sealed) that contains a heat transfer fluid containing an inhibitor. Filler materials for brazing should be AlSi based and not contain zinc. Also, one should use aluminium or stainless steel fittings in hot areas, i.e. at the absorber, and not brass which contains zinc. This is because zinc may introduce corrosion in a solar thermal system at high temperatures. Most commercially available heat transfer fluids contain inhibitors. It is also good practice to cover joints between aluminium and ’red metals’ (copper, brass) with a heat shrinking seal, or similar protection, to keep the joint dry and avoid any external corrosion.

To read more about aluminium corrosion (FAQ section) and corrosion design.