I have been using this product for a long time to convert rust to a black polymer. Corrseal. I took a picture of my Grandsons Escape trailer hitch before and after to show how well it works. It is milk color at first then drys black. It took him all of 10 minutes to do this, most of the time was looking for a 1 QT plastic mixing jug and an old paint brush. I have used it with a spray bottle to do the underside of a Jeep JKU.

I will warn you if it gets on you or the garage floor the spots will turn black also, and will not wash off. USE Gloves. He did not apply it heavy enough and will have to touch it up again. It would have been better from a spray bottle but I didn't have an old one to use. He is learning.

 

I've used Corroseal as well with great results. Just make sure to top coat it for the best possible protection.