Rusty metal preparation

Have used wire wheel on a drill to remove heavy rust. There is some piting.
What would be the best primer to use to kill the rust for good?
Rust oleum or a more professional product?

I find regular aluminum paint to be as good as any rusty metal primer.
It's far better to use a phospheric acid preperation before priming. Any place that sells paint has it under various brands.

2X the phosphoric acid prep. it will penetrate deep into the pits to convert the tiny particles of rust that can be left behind even by media blasting and convert them to inert iron phosphate. It is important that it be water thin in order to penetrate. I have used various brands. I used Rustoleum Extend for awhile but decided that it didn't penetrate adequately. I most recently got Rust Mort by SEM. It is watery thin and appears to penetrate nicely.

Ok, Rust Mort sounds like what I need. Thanks

There is a product that the auto body suppliers sell. I'm sure there are several products now with different application methods, but I used a product that would brush on. You remove the scale, brush it on. It would react with rust and turn black and seal the metal. You could then cover it with primer for leveling it off and then go with your top coats.

You can sand blast too and go with a good base primer if your part is pretty solid and won't be damaged by the blasting.

Can you apply the primer directly over the phosphoric acid treatment or do you have to use water to rinse your phosphoric acid treatment first?

(quoted from post at 05:30:26 01/17/15) Can you apply the primer directly over the phosphoric acid treatment or do you have to use water to rinse your phosphoric acid treatment first?

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need for rinse will vary from one product to another as well as the conditions at the time. The different ones that I have used specify it on the container.

(quoted from post at 07:30:26 01/17/15) Can you apply the primer directly over the phosphoric acid treatment or do you have to use water to rinse your phosphoric acid treatment first?

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As showcrop reccomends,when all else fails,read the directions on the can. The only times I might stray from directions is on sheet metal. My fav product is a green water thin product by Jasco. After treating as directed,I wet sand useing 50/50 water/acid,towel dry and prime quick as possible. If I'm dealing with light rust which has been painted over in years passed,I go straight from machine sanding to wet sanding with 50/50. In all cases,you need to prime soon as possible and by all means do not leave newly treated surface exposed to dew,rain or high humidity or it will rust again. Auto paint and body suppliers sell a specialty product that is diluted and wipped on newly exposed metal from sanding to prevent microscopic rust forming before surface recieves primer. I suppose now that I'm exposing secrects I will tell you one that the old hands will likly say is wrong headed. I never let the project see daylight between primer and top coat. From 1st coat of primer to final top coat can be up to 6 months due to spot putty,primer-surfacer,primer sealer,guide coats and sandings with beer drinking between each phase. Did I mention that before I lay on the final finish I want the surface level as the dead sea and smooth as a baby's butt? If the surface is level and smooth it can often be scuff sanded and repainted down the road without taking it to metal and dealing with rust all over again. If it's wavy and bumpy there's no way of sanding valleys before hitting bare metal on hilltops.

Most auto parts stores that sell commercial paint supplies will have some type of phosphoric acid wash. I usually apply it with a red scotch brite pad & scrub until the metal is clean. If the pitting is deep enough that you can't get it out using that method then I would either try a Clean N Strip disc (3M) or blast it. After blasting the surface is usually pretty coarse so I VERY LIGHTLY sand or go over with a Clean N Strip disc to smooth it out then a final application of acid treatment. Instead of washing with water wipe it clean with lacquer thinner. If there are pits that might hold the acid then I'd flush it with lacquer thinner to get it out of the low spots. Use a different rag each time you wipe it off & wipe until the rag stays clean. The acid wash will leave a protective finish that will be resistant to rusting.