Traditional lead solder has been used for over 80 years for filling, leveling and blending. Even the best polyester fillers cannot match the adhesion, strength and durability that body solder provides. Since I wanted to make a durable repair I thought I’d give it a try.
I found it easy to create a solder puddle on horizontal surfaces, but when it came to vertical surfaces, heat control was a problem. I thought I'd give it another try, this time with the improved, easier and safer-to-use lead-free body solder. Eastwood's Lead-Free Solder was easier to use because of the small 1/4"-diameter stick and wide spreadable temperature range, as well as the fact that lead-free soldering can easily be done with a commonly available propane torch.
I used a cleaning wheel and electric drill to get down to clean metal, a few inches beyond where the solder would be applied, then I wiped the surface with Eastwood PRE Painting Prep to remove any grease or oil. I stirred the thick Lead-Free Body Solder Flux and applied a light coat with an acid brush a little beyond where I wanted to apply the solder. I heated the surface with a propane torch until the surface had a silvery brown look. Then, with a clean, dry cotton cloth, I wiped away surplus flux. The bright silver appearance indicated that the surface was properly prepped. But a little more cleaning was needed, so I rinsed the surface with hot water. I followed this by scrubbing the surface with a diluted solution of baking soda and water (to neutralize residual acids) and thoroughly water-rinsed. This last step is unlike anything I was accustomed to with electrical, electronic, and plumbing soldering.
I lit my propane torch and directed the heat to the surface and the tip of the solder bar, with the solder bar touching the tinned surface. I deposited a little more solder than what was needed to level the surface because it's easier to file than to apply more. I was careful to move the flame in and out to keep the solder just soft enough to melt onto the surface. Next I applied a little Paddle Lube to the paddle's working surface to prevent the soft solder from sticking. Then I used the propane torch to heat the solder just enough to shape it. Once the solder yielded to light pressure, I used the paddle to push the solder into shape.
Once the surface cooled, the flat flexible file refined the shape. Even with a coarse 8 teeth per inch, it leaves a smooth surface. The solder files more quickly than the surrounding steel so I had to be careful not to remove too much. At this point I applied a skim coat of polyester body filler to get the contour exactly right. The finished result was a repair that will last far longer than body filler alone. For more help learning how to use lead or lead-free body solder pick up the DVD The Lost Art of Body Leadwork".
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