I understood your question, and believed it was a good one, but I don't know the answer. My guess is that the sub parts making up that latch assembly were corrosion protected BEFORE assembly and thus each part would have been phosphate, zinc plated, or even dip painted, PRIOR to assembly. Unlike what we might do in restoring a car, where we have an assembly, and we are looking for ONE answer that fits all? I think it's *possible* that the springs might have been dip painted in the same black we see other places, prior to assembly into that spring latch assembly. Maybe someone who KNOWS, or has a nice original *unmolested* part can provide a clue..?