Bandit,
I think the welds look bad because they are contaminated with the metal's coating. I personally don't think you need to pre-heat, but I agree 100% that you need to clean the area with a grinder before you weld. I've learned this the hard way. <img src="/forums/images/graemlins/smile.gif" alt="" /> And cleaning the area will actually make it easier to weld.

If you want to take it a step farther, grind the area and then clean it w/ rubbing alcohol or automotive paint degreaser, just to make sure that it's super clean.

EDIT: one more thing, I think you need to turn up the heat a bit. Looks like the welds are sitting on top of the metal; not getting the penetration you'd like.