Body solder is the old way to fill steel wounds, and was used before modern fillers where invented. But it still has it’s use as it adheres better to steel than polyester filler, it is stronger, and it is not soaking up water.
Here is a video I have created to show the process with fixing some pinholes on a profile. If I should have welded this I had to cut out large pieces and make difficult profiles due to the thin rusty metal.
However, if the area surrounding the holes are sound steel it is easier to weld the holes.
Depending on solder melting point propane can be used for heating, or oxy/acetylene for faster working. I am using a small and affordable Turbo Welding Kit 90 Oxygen / Maxy Gas kit.
Here are some highlights of soldering:
- Use an active carbon mask. Fumes are toxic.
- Clean with Acetone or silicone remover
- When using a powdered flux, the metal must be heated first.
- Liquid flux is applied directly. NB containing acid.
- Heat until flux melts and turns brownish.
- Brush with a wire brush, if necessary wash with water while it is hot.
- The solder rod is lowered onto the metal and both parts are heated so that the tin melts and adheres to the metal plate. Clumps are OK.
- When sufficient solder has been applied, this is reheated until the consistency is spreadable. Then spread the solder over the area with the wooden paddle while applying heat.
- Not much heat is needed.
- Do this in one operation. Laying more solder on top of cold solder is difficult
- Spreading the solder is like smearing butter on a slice of bread. If it gets too hot it runs away and if it is too cold it is not spreadable.
- On flat surfaces use a body file. Else use 80 grit paper. Use a mask, toxic dust!
- If result is not perfect, use ordinary filler on top, after Epoxy primer.
- Wash with alkaline water to neutralize the acid. E.g. caustic soda.
See Painting and rust protection for painting and filler and Welding sheet metal.
