Heat is the only answer. But i would try cycling heat and cold in rapid sucession. Let the liquid wrench do its wonders, but if it still won't budge, try heating it, geting it very hot but not to cherry or melting point, then cool it as rapidly as you can. It does have a tendency to make metal a bit brittle if you do this to often, but if this is a rolled metal hinge, not cast or drilled, the heat will expand all of the metal, bolt and hinge alike, then the cold will shirink the hinge rapidly arround the still expanded / hot bolt. it will in efect, squeeze the bolt to a smaller size, or the hinge to a slighly larger one. Wait for the parts to come back to ambient temp, douse in liquid wrench, and try it again. You will be re-painting the part anyway, a little bit more won't make a a real big differance, right?
Old Dog...
