Nickel and chrome plated steels are relatively easy to spot weld, whereas aluminum, tin and zinc need special preparation inherent to the coating metals. Spacing of welds - Min. 10 x Stock thickness. Adequate access for spot welding should be considered. Small flanges in U channels for example may restrict the electrode from entering the part.
Flat surfaces are easier to spot weld due to easy access.
Multiple bends impose access restrictions, and special fixtures may have to be designed to handle the parts, if access is not a problem. Prior to finishing, the spot welds have to be sanded or ground to blend the welds with the rest of the surface. It is best to choose the same spot weld size, to minimize setups and increase throughput. Plating of spot welded assemblies can cause problems when the sheet metal is overlapped. By carefully designing the assembly to allow easy draining of plating solutions this can be avoided.