Paint prep for old rusty implements?

So what does everyone do for paint prep on old rusty implements. Sand blast, wire brush ??

For me, in the past, it all depended on the implement. I did more wire cup wheels on an angle grinder. I have a tank and cabinet sand blasters but used them sparingly on most implements. I am now working on a disc that I will use the angle grinder and wire wheel on a post grinder.

Flap disc on a 4 or 4 1/2 inch grinder work very well. 40 or 60 grit ones work best when the metal is heavily corroded. Run your finger over before and after areas and one can immediately feel a much smoother surface. This works well on plow parts including the tops of the beams. After painting there is a tremendous improvement in appearance and smoothness. A knotted wire cup brush on the same grinder works well too as the first pass on heavy corroded parts. With a complete dis-assembly sand blasting, and/or applications of Ospho (or your favorite rust converter) or muriatic acid work well. They will get in spots that one cannot clean with wire cup or flap disc. Both of them need to be used outside in fresh air for safety and health reasons. If you plan to have parts zinc coated do not use an Ospho type product. I learned the hard way; the zinc coating will not adhere to the resultant iron. On large sweeping pieces like moldboards working up to about 120 grit paper with a random orbital sander seems to make a nice finish. If part size permits I like to run everything through the sandblaster as the final cleaning and preparation step. Then a wipe down with your favorite oil and grease remover followed by two coats of primer and two coats of finish paint. Everything I do is brush painted so some Penetrol is added to the finish paint to eliminate brush marks with the oil based paints. Hope this helps.

It needs to be taken down to bare metal. A lot of it you can use a paint stripping wheel on an angle grinder but if it's pitted with rust it needs to be sand blasted.

How ever you do it, when done coat with OSPHO before painting to keep rust from coming back--

I made the switch from cup wheel to flap wheel a couple years ago. I find that it goes much faster. I also strongly recommend a phosphoric acid rust converter, especially for getting into pits and corners, but I will add that I believe that it is important to rinse fairly aggressively with water after. If you are worried about flash rust you can wipe down with an alcohol soaked cloth.