"Ignoramus23641" wrote in message
...
I am trying to solder a brass fitting to the fuel tank.

I'd ask a couple of questions:
-What was there before you started this process? If there was any other
kind of material, some remnants could be fused into the area you are trying
to tin. especially epoxies.

-What kind of solder are you trying currently? If it is soft solder, does
it have a flux core, and, if so what kind? (Acid or Resin)? or ? If you
using "electronic" solder, it may be a resin (rosin core) flux. I'd
certainly go with acid core for this application. I usually keep liquid or
semi liquid fluxes of both type around.

-Can you get tinning to occur on other pieces of sheet metal?

1. The area to be "tinned" needs to be bright and shiny, and it should be
cleaned immediately before attempting to heat/tin it.

2. Use a soft flame. It is very easy to overheat something as thin as a
fuel tank. One instant of too much heat and it's all over, until you
re-prepare the surface.

3. If you go with a silver solder, make sure you get a flux that matches
the temp range of the solder.

4. Years ago, we had to soft solder electrical wires onto steel leads from
high pressure liquid sensors. The only way we could get tinning to occur
was to use sal-ammoniac as a flux(sp?).

I personally still like to use heavy soldering coppers (soldering irons to
the rest of you) for such work. I heat them with a propane torch until the
solder to be used melts freely, then use the heat from them, (properly
tinned, of course) to transfer the heat to the work. You'd be surprised at
how effective this approach is. This way, there is NO chance of overheating
the work.
I like to collect old soldering "irons" for just this use. Note that, in
their day, they were usually sold in pairs. One would be being reheated
while the other one was in use.

Let us know what eventually works out for you.
Pete Stanaitis
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