Fitting a Sacrificial Anode to an Aluminium Radiator

I like aluminium radiators. They are lighter and more efficient than their brass counterparts and can be bought for reasonable prices. I have one fitted to my ‘69 Plus 8 racer and to my ‘82 BMW Alpina rally car.

One potential downside to aluminium radiators is corrosion due to electrolysis. This can happen very quickly and destroy an aluminium radiator in a matter of months. Google this topic and you will find lots of information and somewhat conflicting opinions about stopping electrolysis - ground the tank vs insulate the tank etc. etc.

An alternative is to assume that some electrolysis is inevitable and fit a sacrificial anode. Sacrificial anodes are used extensively in boats. The idea is anode corrodes instead of the metal you wish to preserve. In the case of a radiator the anode is zinc and can be purchased for that specific purpose. They can also be fitted when the radiator is manufactured and why this isn’t standard procedure is beyond me.

With the engine out on the rally car I decided to install an anode in the radiator. The photos below show what is involved. Basically you buy the anode plus a weld-in bung of the correct thread, cut a hole, weld in the bung and screw in the anode. The anode should be in the lower tank and placed where it can be removed for inspection from time to time.

Simple and low cost insurance for your valuable aluminium radiator.

Anode and weld-on bung made by Aeroflow

Hole cut in face of lower tank

Bung welded in

Left: Final result. Anode screwed in. TIG weld not as nice as neighbouring professional examples but nevertheless will do the job.