Can aluminium absorber tubes handle the high liquid temperatures in a solar system?
Hydro: It is necessary to use a commercially available inhibited glycol, specially designed for solar applications. Internal tests at over 175°C with aluminium, copper and stainless steel has shown no corrosion problems, when using Hydro's HyLife™ Solar alloy in a correctly designed system. Please contact Hydro for a reference list of heat transfer fluids.

Can aluminium absorbers be used in open systems, with fresh water in the tubes?
Hydro: No. This will generally cause corrosion. All aluminium absorbers are only suitable for closed loop systems with a heat transfer fluid containing an inhibitor.

Where can I buy the glycol designed for solar systems with aluminium tube absorbers?
Hydro: The major suppliers in Europe have products suitable for aluminium. Please contact Hydro for a reference list.

Is it possible to use other materials in the liquid circuit that contains aluminium tubes?
Hydro: Tests over 175°C with Hydro’s HyLife™ Solar alloy, copper and stainless steel in a closed circuit system have shown no corrosion problems when in a correctly designed system. For instance, 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. External galvanic corrosion may occur between aluminium and other metals if water is allowed to condense on the joint area. It is therefore good practice to keep the joint dry and protected with a heat shrink sleeve, or similar.

What about external corrosion in coastal salt-water regions?
Hydro: Eventual joints directly to copper or brass fittings should be covered against external moisture.

Read more about corrosion design.