I actually have been doing a bit of checking on zinc primer and did run into ZRC which came highly recomended. Carboline I haven't but now I will check it to. The jury is still out but it was interesting learning about the hot dipped galvinizing process. There is a fair bit of prep.-proper size and placement of filling and air vent holes etc. I do usually solid weld joints if feasible -if not I clean-prime and seal with automotive seam sealer. This has worked fairly well. The big difference in hot dipped vs cold galvinizing is apparently lifespan - aprox 1/2 for cold. Mainly I am going thru this exercise to try to learn more and get a better job without breaking the bank. Thanks for your input.