Stovebolt.com Forums The Shop Area Paint and Body Shop Rust sealer?

I am just about ready to start on my cab patch panels. I know you can't use Ospho under epoxy primers or sealers, are there any other suggestions to use for a rust sealer?

I have used rust mort before years ago and it is still around may be a option

The technical sheet says that fillers or primers can be applied directly over this once it's dry (24hrs). It makes no distinction between primers or epoxy primer, looks like it is what I need. It's still available, even Wal-Mart sells it. Great call KEVNSKI...

Be careful with that Rust Mort. Looking at the data sheet, it states that it's main ingredient is phosphoric acid.
That is the main ingredient of OSPHO.
You run the potential of adhesion problems if you apply epoxy primer over a
surface treated and left with that type of rust convertor.
You could apply a Rustoleum type primer over it but that will not provide the adhesion and moisture blocking properties that epoxy primer will provide over a properly prepared substrate.

Short of sand blasting the cab what are my options?

Unfortunately you can't hide rust. You may slow it down by sealing it under something but it will keep growing and eating metal causing failure of the materials on top of it. Rust "converters" are typically only surface deep and the chemicals don't play nice with the next layers on top. They falsely make you think you've killed the rust unless it's very, very minor. But if the rust is that minor, sand it off.

You basically have three options if you are trying to make a permanent rust repair - 1) Mechanically remove the rust - grind, blast, wirewheel, etc or 2) Cut out and replace all the rusted metal or 3) Professional Chemical Dipping (very hard to find these days and trapped chemicals can leach out later causing problems). In any case, you must remove the rust, not hide it.

Not what you were hoping to hear, but media blasting is the likely the best way of doing a thorough job. It's so easy and gives you such nice clean metal with good tooth to work with. Grinding and wirewheeling is the next best option but easier to miss rust and remove excess metal. Any of it needs to be done with care to prevent adding new damage...

Craig
Go to spiuserforum.com and look at their Primer sub forum. There is a lot of chatter regarding epoxy primer and how to prep the surface.
This site, Southern Polyurethanes sells a quality epoxy primer. Their forum provides a lot of paint knowledge from their resident experts.

Within this forum their on-site expert writes that you can use OSPHO but you MUST follow the procedure to a "T" . Apply OSPHO, let sit but do not let dry then rinse with copious amounts of water, wipe/blow dry then wipe down with their 700-1 Wax and Grease Remover then after 1 hour lay down the epoxy primer.
This is the abbreviated process so go there to get the full step process But even they feel this is not the preferred approach.

But sandblasting is the best sure fire approach, then the 700-1 W&G Remover then epoxy.

I am aware of only company that does chemical dip of cabs and doors in this region, they are in Ocala Fl. They are pretty pricey, but it would be completely stripped. There are a few companies locally that do media blasting, one or two will even do it on site. The cost is a lot better but you read "horror" stories about body panels being warped from the process.

My cab has considerable amounts of rust in the toe boards, steps and cab corners, all of which is replaceable with patch panels. My welding skills are less than stellar but I'm getting better. I have a friend that is a former body man and is more than willing to help with the panels and finish work. I just want to do it once and do it right.

I payed $1200 to have my cab blasted in my driveway. The blaster did a good job and spent all day at it. It was on my rotisserie so he could get at just about everything.
Your cost should be less than that for blasting, as I live in the land of the Alaska Gouge. I've also had him do the doors and other sheet metal with good results.
A competent blaster won't warp the metal.
I would recommend that approach. Ask for references from whoever you consider.

Kevin,

What was the media that the blaster used?