The Stovebolt Site 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?

I believe it was a ground glass media. It was very fine. Probably 80 Grit Garnet Link

I did some digging on the web last night, there are a few companies near me that do blasting. One is just the next town over and they do mobile dustless blasting, they use the same equipment advertised on "My Classic Car" with Dennis Gage. The key here is they come to you.

I did a quick search and didn't find any threads detailing someone who actually has used this on the "BOLT". Would there be any true unknowns using this method , prep and final finish? It looks promising I I'll reach out to the contact and see if I can get some more information and maybe even a price.

WRT the dustless blasting, the main complaint I have heard is that using water as a propellant invariably leaves collections of "slurry" in those same rust prone areas that you are trying to clean, making it a moisture collector that is now going to start the very rust we're trying to get rid of. So I would not recommend using this process on something that cannot be thoroughly cleaned out..


Speaking to (dry) media blasting and the damage that may occur, most times the damage occurs when someone is blasting from the inside and working around the "openings" of an inner structure. Damage such as this follows those openings exactly, and kinda verify that it was indeed sandblast damage. When someone is blasting along cleaning up the inside oblivious to the fact that nothing is hitting the panel underneath structural braces, the "stretch" occurs only at the opening. The peening action starts the stretch on the same side that the media hits, so it stretches INWARD toward the media source.

Here is a media blasting damage "study" I did, and various methods to correct.

http://67-72chevytrucks.com/vboard/showthread.php?t=647269

For heating methods, Robert kinda shys away from torches for sheet metal shrinking because I like the slower sneak up on the fix approach. Faster methods tend to have me sliding past the exit ramp sideways, and then I need to stretch again.

My preferred method is using the heating tip on a dent puller, trunk lid upside-down in the case of my study, so we have the stretch pucker upward, and then use the heating tip on the high(est) spot. By shrinking while the weight of the dent puller is against the panel (but don't push, you won't need excessive force) you can actually see the panel move down/outward as the shrink occurs. But it boils down to using the "shrinking" tool you have, and what works best for you.

The panel really doesn't care which side heat is applied, it will shrink regardless. But in my experience, just having that little bit of static weight of the shrinking tip against the inside, it seemed to restore proper panel crown more quickly in approaching the repair from the stretched side.



So, with all that said, prevention being an ounce of cure, etc, how do we prevent that damage? In equating sandblast damage to a hammer swing, Media size = hammer size. Air pressure = hammer swing velocity/force. So to make sure we aren't using a sledge hammer, the media size should be medium to small, and to reduce the force of the hammer blow, air pressure as low as possible. Next, if media blasting the inside of a hood/trunk lid/door where a structural member (with openings) is against the inside of the outer skin, block off those open areas so you can media blast the normally irregular surfaces of that structural member without media going past the access holes where it strikes the back side of the outer skin. Then follow up that with abrading the back side of the outer skin with a DA and 80 grit.

I have done much of my own blasting but I've also paid for some since it's messy and the price really is not too bad once you price your media, mess, time and of course health risks. You must protect the lungs. Need to choose media and blaster carefully - don't use the guy who mainly blasts heavy equipment and bridges. I pay around $80/hr here and they can do it faster than me and includes the media though I do a more thorough job myself. It works out to roughly $50 per body panel, inside and out, so a good way to price your own time.

I had body panels stripped by a guy that did plastic bead. The bead removed paint finishes but not bondo or rust and it still left factory markings and original protective coating on the metal. It was a great way to start and picture what really needs work and reduced the toxic mess of the remaining blasting since the paint finish was gone.

For rust and bondo I use a fine ground glass and only use new media (no recycling media as this reduces packing contaminants into the clean "pits" you are making. I use the fine glass since it was abrasive enough for rust removal but not nearly as aggressive as sand, slag, etc to prevent warping. Sand is not healthy to use. I have had friends use the dustless blasting and it left everything messy with a slurry in corners and starting to rust.

I find with the glass that I am actually cleaning everything very well and the part is spotless when done and a really nice texture for epoxy primer. The only drawback is that blast media bounces and removes all coatings into the smallest corners which is good for starting fresh but epoxy primer does not bounce. You may need to brush or airbrush inside the corners of doors, etc as you don't want to leave them naked and freshly blasted as they will rust quickly.