Sand away the EDP coating. If you decide to butt the panels like we did, leave a gap of 0.035-inch between them so the metal can expand when it heats up. Maintain this gap by inserting a small screwdriver into the seam next to the welder tip. This trick also keeps the panel from buckling. Never weld in a continuous bead here; it will cause the panel to distort from too much heat. Put the welds an inch or so apart and then go back and fill it in. Move around the area so the metal doesn't overheat.