My '65 Impala is disassembled, stripped down to bare metal, and new metal welded in where needed. After stripping the body with paint stripper, I sanded all the panels with an orbital sander with 40 grit paper.

A number of surface rust spots remain that won't sand out. Some are areas up to about 6 inches square where the old body filler had separated from the metal and rust caused deep pitting. Others are where paint had flaked off and where rocks had chipped the old paint and the metal underneath rusted.

What is the best thing to use to "convert" the rust so that it won't cause problems in the future?

The auto body supply shop sold me some Dupont 5717S Metal Conditioner. Now that I read the instructions, it says to follow this up with Dupont 5718S Conversion Coating. Is the 5718S necessary, or is the 5717S enough on its own?

Another option is to use some POR 15 Metal Ready (etches and leaves zinc coating) that I have left over from another job.

Or is there a better way to handle these rust spots?

Thanks for your help.

POR 15 Metal Ready is good stuff,,,I've used it and is Great, but I'm no body Pro.

I agree, POR Metal ready hasn't let me down yet !

I use POR15 many times for bad areas that have pitted,usually I will sand blast that area but if you are limited the POR15 is perfect and follow the instruction by the tee or at times you can have delamination.Another item if the metal is cleaned well is an etching primer or a corrosion protection you can go straight to body work after it dries.Visit www.redzautorestoration.com

For about $60 your local auto body supply store can get a spot sandblaster that works great on cleaning the rust out of those pits without warping the metal. The rust convertor does help but it only buys you time. When a person has cancer doctors don't try to convert it to something else, they get rid of it.

Forget the conversion coatings and etch primer. Get some Navel jelly, it will eat the rust away leaving nothing but clean metal. Do a wash with water and soap, da sand with 80 grit and EPOXY PRIME.
Etch primer is outdated technology...Eric

Use Krud Cutter. It's stonger than naval jelly so it works better, plus it comes in a nice neat spray bottle, but comes out in a gel.

For about $60 your local auto body supply store can get a spot sandblaster that works great on cleaning the rust out of those pits without warping the metal.

I bought one and used it on the hood for my 69 Charger. I was done the whole thing in about a half hour total, layed down some epoxy and did the bodywork. The spot blaster gun was $50 well spent.

Thanks for the good ideas! I do have a spot sandblaster and may give it a try. I'll also have a look around and see if Navel Jelly or Krud Cutter is available in this neck of the woods.