I spent most of the afternoon applying lead-free body solder to the damaged areas of the hood.
When I bought the car it had been fitted with hoodpins, which are not original to the roadster. Previously I removed the pins from the body and welded closed the holes in the hood. Today I got started by cleaning up those patch areas using a 3M Clean ‘N Strip wheel in my drill.
It was important to clean the area because the Metal Prep I used to inhibit rust formation leaves a thin protective covering over the bare metal, a coating I wanted to remove before applying body solder.
There were some other areas of the hood that would also need soldering. The hood had clearly suffered from a collision to the front right of the roadster and I had previously welded up a crack along the edge of the hood lip. But the lip itself remained a bit wavy. Here is that area before and after I cleaned it.
There was also a small dent on the passenger side toward the top of the hood.
And a larger dent on the other side of the hood.
After cleaning the metal with the wheel, I wiped all of the areas with acetone to remove any dirt or grease on the surface.
The body solder will not bond directly to steel, so I needed to apply a tinning compound that bonds to the steel and then bonds to the solder. I brushed on the tin generously.
Next I heated the tinning compound using my Propane torch and wiped it using a clean shop towel to remove any impurities that burned off.
Here is a shot after the tin was applied. Afterwards I washed the area using clean water to remove any acid residue that the tin can leave. Skipping this step could lead to rust later.
Then I applied the solder using my propane torch. I had to move fairly quickly, and with the hot solder in one hand and on the verge of running off the hood and the propane torch in my other hand it was difficult to take pictures. I got one about halfway through, and another after I judged I had applied enough. My philosophy with the body solder has become to apply more than enough and grind it back as close to smooth as possible, rather than try to work it with a paddle, which I find is very difficult to do.
I followed the same steps of cleaning, tinning, cleaning, and applying solder to the hood pin areas.
And to the small and large dents in the hood.
Next I finished working the repair on the hood pins. I started to shape the solder roughly level using my angle grinder with three stacked cut-off wheels, which creates a broader flat edge to cut away the metal.
Using the grinder I was able to get the profile of the repair fairly flat.
Then I finished smoothing the repair using some 120-grit sandpaper and a sanding block. The result was not perfect, but close. This area will require only a thin coat of body filler to be undetectable under paint.
Here is the profile.
The larger dent in the hood deflected with heat, probably because the sheet metal was thinned from grinding when originally repaired with body filler. So solder was not very useful in that area, and I will use body filler to address that area later. But the smaller dent took the solder well and the final repair was very smooth.
I finished the day grinding the solder as smooth as I could on the hood lip.