I am using Master Series Silver. I have similar corrosion in a few places. The product is highly recommended by others here.

Mastercoat® Ultimate Permanent Rust Sealer SILVER Primer, Original & Sprayable Slim QUART - Mastercoat® & The Master Series Coating Line - No More Rust™

Mastercoat Permanent Rust Sealer is a professional paint over rust application that will stop rust permanently at low prices.

nomorerust.com

 

A phosphoric acid based product will destroy the rest of the rust in the pits, then you can coat it with whatever rust preventive paint you want.

Mastercoat Metal Prep & Rust Remover - Dissolve Rust FAST!

Mastercoat Metal Prep & Rust Remover is a powerful chemical that will dissolve rust on your vehicle in as little as five minutes. Fast acting and low cost.

nomorerust.com

 

Can you layer the product in several applications to arrive at a smother surface finish?

 

After getting mine clean, I did the Ospho on mine, sopped up excess let it dry overnight per the instructions. The a thick double coat of black POR15. Dry between coats.
I later learned from actual pallet and body guys that it’s better to do the epoxy primer Master Series stuff. But my welder put POR15 over welding primer on a new floor board and riser so I just did the same in the other side. I still think it’s going to be sealed for years to come. Just don’t forget to replace your seam sealer topside and underneath in the factory locations.

 

Ospho or another PA product, then Master Series Silver.

 

Another vote for a rust converter (I use Picklex20) followed by Mastercoat Master Series silver. If you wanted to "smooth out" the pits you could squeege in some 2-part polyester glaze before your top coat.

 

I believe master series silver has a thicker product (master extreme) for pits. You spread it on and then scrape it flat. You then Follow that application with a coat of MSS. A second option is that You could put one coat of MSS, bondo coat, and then add another coat of MSS.

 

Treat it with PA (milkstone remover at your local farm and feed is way cheaper than most "automotive" acids and is the same thing) then a couple coats of master series. You can let the master series separate out and use the thicker stuff from the bottom of the can to fill small holes and pits.

 

For floors, I don't care about pits. I spray two coats of silver and then if there's tiny pinholes in my welds, I glob some silver in that to fill them up.

This is the floor I'm rebuilding in my LTDII, and yes that's Mastercoat Silver.

 

Another vote for Master Series.
This is the silver but I added another step to mine though. Not really necessary I think but I top coated the silver with their AG 111 topcoat as well.

 

I’ve used both SPI epoxy and MSS during my restoration, and both have been very good. I’ve been gravitating more to MSS, especially for the frame/rockers/torque box. I really like that I can use phosphoric acid to convert the rust, but this also protects it for a length of time as I might not be able to coat it with MSS right away. With epoxy, you usually can’t coat with PA (depending on the epoxy) unless you neutralize the PA before epoxy primer. I would rather not worry about whether or not I correctly neutralized it. And if you take the metal to bare metal, you would want to protect it quickly, whether it be epoxy, PA, MSS, etc.

The MSS is really easy to apply with a foam roller and looks nice, but honestly who cares what it looks like because it will all be covered. Using the foam roller is a little easier and cleaner than using the paint gun, and there’s no overspray. Epoxy also works best with clean bare metal. Phosphoric acid then MSS would work well on your mildly pitted floor.

 

RUSTOLEUM!

 

Thanks for all the good responses everybody, looks like the way to go is

1. Ospho (or similar product)
2. MSS

Initially I was tempted to just pick up a single product that comes in can but the extra work will be worth the peace of mind.

 

Keep us updated with the progress; pics please!

 

I sandblasted. Then rust converter (Picklex 20). Master Series Silver also used on bridges then Eastwood seam sealer on seams. This on the driver’s air vent cowl after removing the fender and cutting a flap in the side.

 

Once you remove or neutralize the rust any quality coating system that is properly applied will do the job.

It rusted in the first place because of moisture,

Keep the moisture out and you will get another 50 years of trouble-free metal protection.

Spend what you need to spend, don't overspend, use that money elsewhere.

 

To give you another option, check out corroseal. It isn’t to be used in places that need a smooth, finished look like exterior panels but hidden areas it is great. It is very popular in the 4x4 scene because of its durability. Prep is pretty easy and it is water based and brushable so no need to clean up a gun or have great ventilation. They recommend several coats and after 24-48 hours it can accept a top coat if you want, but it isn’t necessary. The best I can describe the finish is like semi-gloss black powder coating. It comes out white, then turns purple when it contacts rust or bare metal then finally turns black. It turns clear if not in contact with metal or rust and just acts as a primer. If it doesn’t convert and the color is still rusty then that means the surface had grease or contamination. This is a great way to make sure it is applied correctly. I believe it is latex based, so it has a nice durable finish that is slightly more flexible than you’d get from an enamel. Great for preventing chipping in areas like the chassis or fender wells.

I did my control arms several years ago on my F100 which is one of the most damage prone spots on the truck. I did 3-4 coats and no top coat. They look the same today.

From what I read, it was created for industrial marine applications. If it can take the salty seas, then it’ll likely be fine for sitting in my garage and putting around from time to time . You can get it many places, I got a gallon off Amazon for around $30. I did the entire frame on my F100, the floor pans, the engine bay, and used it on my 73 Mustang project as well with plenty left over. Again, it isn’t for finished body work but for hidden areas.

I don‘t see it recommended much on here so I thought I’d give it a shout out.

 

Lizer, that Master coat Silver looks great!
I've been using POR 15 for 20+ years. One thing I've learned is that the best time to add primer or paint to POR 15 is while it's still tacky. Even if just a rough primer coat, it'll provide a surface that paint can stick to.

 

KBS Coatings . . . . All Day, Any Day without even the slightest hesitation. KBS is on my very short list of "never use anything but x" products. More specifically:

• Rust Seal
• BlackTop
• KBS MAXX
• Motor Coater

Finding these coatings was like a gift from the old and new gods; after years of self loathing excuses over sh** results with POR-15, VHT, Krylon, Duplicolor, Rustoleum, Eastwood (excluding any 2k Eastwood product - those are 🧨). I could never get a result like the pictures or always seem to find a way to blame myself for never stellar results. I understand I'm sounding preachy here, but the sh** just works. I've only used the above listed, but all feel . . . fool proof. Like I'd have to try and mess them up. Lastly, the icing on the cake for me with KBS stuff is that it is very noticeably thick and more gelcoat like than thin paint (aerosol or brushed).

For example:
I painted the block, heads and water pump with one coat of a zinc primer and two coats of KBS Motor Coater (olds gold aerosol). The sway bar is one coat zinc primer and three coats of Duplicolor Engine aerosol.

Caveat & Funny Story:
I hadn't heard of Master Series until lately and have no experience with it. Be warned (or delighted) that googling just "Master Series" and clicking the very first link, which is an Amazon link, like I just did . . . . . is a master series of another hobby . . . . . .

 

Almost all pro shops use epoxy primer, That's what I use.

 

I have had bad luck with POR15. Now I blast everything and use southern polyurethane epoxy primer. It works the best. Rustoleum can be used but you need to buy some hardener. I use the tractor supply hardener. It makes it dry in one day