Wrought iron is an iron alloy with a very low carbon content and has fibrous tiered slag inclusions. Wrought Iron bends better than mild steel and is very corrosion resistant, hardly rusting over long periods. It is tough, malleable, ductile and easily welded, but the slag inclusions make it extremely difficult to obtain a porosity-free and crack-free weld.

When welded, it is often tackled in MMA, as most wrought-iron still in-situ is in the external environment.

If you are surface-repair welding and don't require a perfect result, then a 6013 electrode will suffice.

If you need a weld of higher-quality, through the grain, you must use a 7016 electrode and repeatedly weld, grind back to clean metal, weld again, until you get a weld of acceptable appearance. Metallurgically it wont be sound in the same way as we are used to with mild steel, but it will probably be stronger than the wrought iron itself.