Metal prep for paint, concrete, and up against wood?

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Building my gate, and I am close to finishing up here, and am not sure on how to prep the metal. I was going to send everything for blasting and a two part industrial paint, but it's just far too expensive.I will have part of a 4x4 tube in concrete in the ground, and I will have some 2x2 angle lag bolted to a pressure treated post. And the rest is just open to the air. I figure a good primer and paint will be fine for the open air and against the post. But in the concrete how do I keep it from just rusting away where I can't see it? Would cold galvanizing be my best bet? And what about the inside of the post? fill it with concrete? The post and angle have surface rust, and the gate has that black grease stuff on it. I was using a flappy sanding wheel to clean off the gate, but it just doesn't last, same with on the rust. But not sure if that was just from using the wrong type of wheel. What is my most cost effective way to do this?   TIA
Reply:Most cost effective is hot dipped galvanizing even compared to the best epoxy coatings.  I have used the cold galvanizing paints such as Galvacon and Zinga  They were used to touch up welded areas and although the colour did not match the zinc they stood up well.  Ten years later still good.  Most wood preservatives are copper based and the copper will react with the bare steel.  Even putting a layer of duct tape on before bolting to the wood would help.  Concrete is a moisture source so again if the metal is not isolated it will rust.  I don't know your location.  In some place like Seattle moisture and corrosion are a problem.  On the west coast corrosion increases with temperature and the closeness to the ocean.  If you are in the desert then you can just about leave the metal bare and not worry.   Forgot to mention that the best way to stop internal corrosion in a tube is to weld it closed.
Reply:Thanks. I am in Alberta, we get a little bit of every type of weather here. I'll have to find a place that does hot galvanizing, and compare to a few cans of the cold galvanizing. Although it would probably need to be blasted then, and that is still pretty expensive around here. And I will weld the post closed top and bottom. Maybe I'll see if I can get some tyvec to put between the wood and steel, or tuck tape.