I weld up may gates, pens etc and I use rattle can primer and Rustoleum. Most of my gates and pens are 10 or more years old and still look fine. If I see a rust spot I rattle can it with the rustoleum that penerates the rust. I do not use colors or gloss its all flat black or primer red. Surface prep is key using solvents and a brass brush on the grinder to texture the surface a little.