I thought I would share what is looking like a small success: Most of the A.C.s in existence are old and getting older and aluminium features in much of their structures. Over the years I have tried to keep the one off alloy header tank on LM5000 water tight, but even with lots of anti corrosion anti freeze in the system the dissimilar metal corrosion around the radiator cap has been dire. The aluminium welding from 1958 still looks good, but I would not recommend trying to weld new metal onto the old - just too much oxide hiding within. So what to do ? Well complete replacement is one option, but I would sooner preserve the original structures where possible. Last year, discussing this with Rob Hendriks, he said he had experienced considerable success in this kind of repair with 'Belzona'
http://www.belzona.co.uk/en/products/1000/1121.aspx I gave it a try last year and so far the repair has been perfect and the tank looks just like it did in 1958. There are various versions of the compound and the one I chose has a reasonable working time before hardening as well as a longer shelf life.
It might be worth a try on Weller blocks with corrosion problems ?
