DIRTY STUFF

FOLKS, there is a way to solder aluminium. It was long thought to be impossible due to the instant oxidisation that this metal attracts; trying to solder it using conventional flux-based methods would simply see the lead solder dribble off and fall on the floor. But the method I use works, is ridiculously simple, and is permanent.

- WILLIAM PORKER

First, where the metal is going to be joined, we need to get rid of the oxidisation skin by using an abrasive like emery cloth or filing to get down to bright shiny metal. Then, using a heat source like a gas torch or an oxy-acetylene flame, heat the metal until it will melt the tip of a lead solder stick rubbed across the joint. Starting at your pool of lead solder, use a sharp-ended flat-head screwdriver to scrape the alloy surface hard across, and the lead pool will follow. Use the same technique to extend the area where the lead is sticking, until you cover the area of the joint.

I last used this method to join a brass radiator cap neck to an aluminium coolant header tank. I soldered a layer around a pre-cut hole in the flat top of the tank and then did the same to the underside of the brass neck. I then fitted the neck in place and used the torch to sweat the two together. Simple, effective and permanent, without using flux.