As the others said, it's best not to use metal for molds. Unless you can be sure you have liners that will absolutely prevent soap batter from touching the metal, it's just not worth the risk. Not only might you ruin your soap, you can potentially ruin your metal cookware as well.
I have used freezer paper to line various containers (usually square or rectangular in shape) and even it can leak when the batter is too wet. Of course that's not usually a problem with HP because the batter tends to be far less liquid by the time it goes into the mold.