Order of Paint Prep Steps

[S10xGN]

Slightly OT...

We just got a '47 Ford Coupe to play with and it's WAY rusty. Not much paint left, just surface rust and it will need to set outdoors for awhile, too.

My #1 dilemma is how to remove the rust, especially on the inside of the car. We don't have access to a "Redi-Strip" or anything like it here in SE TX. I've heard a resounding NO on sandblasting. So, howsabout a high-pressure washer with some Ospho in the siphon?

#2 Dilemma would be, etching primer first or just epoxy primer? If etching primer, when to shoot the epoxy primer?

#3 Dilemma is once primered, would there be a problem doing panel repairs and sanding the primer off (in affected areas) and re-priming after bondo?

TIA!

 

[John Larkin]

Where do you find your Ospho? I've been looking for years; last time I found it was in Florida in 1999. I moved and couldn't bring it on the moving truck.

How bad is the rust on the inside? I rented a pressure blaster (big compressor required) to do a truck bed. It worked good. I think sand inside the car would be ok, just don't hit the exterior skins (meaning floorboards, dash and bracing only). Some cardboard over the inner doors and quarters would stop direct hits. Duct tape is pretty impervious to sandblasting too. Nasty job; expect to find it behind your ears for a few days.

If this is a work in process and you are working one panel at a time, you need to sand the panel to bare metal with 80 grit, metal work it to your satisfaction, Ospho it, let it dry really good for a day or two, wipe it with neutralizer, then apply body filler. Self-etching would be best applied now to catch rust any surface rust on exposed metal. You only need a piss coat; doesn't take alot. The application should be almost see-through. Then lightly scuff it down and prime it. A filler primer would be better but not that Feather Fill crap, use something like UroPrime.

 

[S10xGN]

John, the Ospho came from a local hardware store, but I googled it awhile back and found several on-line outlets. IIRC, it was $19.95 per gallon here.

The entire inner roof is solid surface-rust, along with the outer roof (makes me suspect Ford never bothered to paint the inside). The rest of the body has *some* paint on it, but also some surface-rust. I was hoping to sandblast it, but so many people have told me not to because of panel warpage.

The way I work (12 hr shifts) I might be able to do it panel by panel and lay on some primer, but with our locale (SE TX) weather is ALWAYS a problem, hence my preference for an "all-at-once" approach (for instance, I'm just finishing up my 7-day break and it rained 6 out of the 7 days. Pretty hard to get anything done outdoors like that)!

I was really wanting to get the body de-rusted and in primer, then do bodywork in one area at a time, but that may not be an option. Still looking for a dipper in the greater Houston area...

 

[John Larkin]

Think about trying a wire wheel. They're cheap enough to test one out. That or one of the stripping Roloc discs. The warping from sandblasting is due mostly to the heat generated by the sand hitting the panel in my experience (i.e. friction). Might get away with laying some wet towels on top of the car to cool the panel, know what I mean? I bet a '47 Ford was built from some thick steel more than likely.

 

[Drop Top]

I've been restoring cars from street rods to muscle cars sence the 80's. Started profesionaly in the early 90's. I know what your talking about. If the rust isent too bad try sanding it off with a D/A in the locked in postion with 80 grit. If its heaver then this a very light sand blast to remove the loose scally rust and then paint with Por-15. Don't take the rust all the way down if your going to use the Por-15. If the rust comes off with the d/a then metal etch the bare metal and then prim with a good bare metal sealer.

 

[S10xGN]

I need to upgrade my compressor anyways (it's 27 years old!) and I may end up with a light-duty snadblasting rig, too. I'm looking at Northern Hydraulics' house brand 7.5 HP 2 stage that will pump 26 cfm's @ 175 PSI.

If I were to sandblast the body, would it help on the (potential) panel warpage to try blasting at, say 50 psi? I know it would take longer but if it could be done without warping, I'd be willing to do it. Or how about heaping some wet towels on the opposite side of the work area?

 

[Drop Top]

The old cars that we are talking about had real metal in them back then. They were not worried about gas milage. So the metal is much thicker then the cars we have today. I have sand blasted them before with very little to no damage. Here are a few pointers. If you run out of air thats fine just stop and let the preasure build back up. Take your time you don't want to rush and chance worping the metal.
1) Buy the finest sand you can get.
2) Blast on about a 45 degree angle. So the sand will glance off the panel.
3) Keep the presure just high enough to do the job. Start low and work your way up.
4) Keep the nosel moving. Never let it sit in one place for too long. This will creat the heat that will worp the panel.
5) Keep the nosel at least 3 feet away from the panel. More if possable.

 

[S10xGN]

Originally posted by Drop Top
...
5) Keep the nosel at least 3 feet away from the panel. More if possable.

REALLY? Three feet? Doesn't seem like anything would be accomplished this far back. Maybe I'm just used to small backyard blasters...

Would this apply to a Harbor Freight pressure-pot type blaster running around 50 - 60 PSI?

 

[Drop Top]

I'm sorry I guess I'm used to a more larger size blaster. Keep it close enough to just get the job done. I have used the presure pot that harbor freight sells and you do have to be a little closer.

One word of advise. Make shure you run the sand through a peace of window screen to sift out the larger peaces of sand with this blaster. They plug up very easy. Also make shure you use a good water trap before the air goes into the pot. Moisture in the line will give you big fits also.

 

[st1nger]

sand blasting

just did interior of 83 t with harbor 20 lbs pot used #30 silica sand what I foundwas do floors rails all the inside stuff bed everything but outside panels put plastic sheet under vehicle and surround it so you catch everthing you can after you run out of sand say 100lbs then gather everything up and sift everthing thru small mesh screen sand breaks up as you use it so it get finer mesh take used sand and spay panels that have exter panels on inside 12 to 18 inch is close enough always keep moving may have to go back over a 2nd time but found no warpage and panels were clean metal prepped and epoxy primed them look great not a fan of sandblasting but it works got pic if you want to see

 

[S10xGN]

Re: sand blasting

Originally posted by st1nger
just did interior of 83 t with harbor 20 lbs pot used #30 silica sand what I foundwas do floors rails all the inside stuff bed everything but outside panels put plastic sheet under vehicle and surround it so you catch everthing you can after you run out of sand say 100lbs then gather everything up and sift everthing thru small mesh screen sand breaks up as you use it so it get finer mesh take used sand and spay panels that have exter panels on inside 12 to 18 inch is close enough always keep moving may have to go back over a 2nd time but found no warpage and panels were clean metal prepped and epoxy primed them look great not a fan of sandblasting but it works got pic if you want to see

How long does this take? I mean is the process fairly quick or do you need to stay in one place for a long time. Give me a "for instance" on, say, how long it takes to clean a front fender.

Thanks!

Russ

 

[st1nger]

sand blasting

well 1st word of advice No out skin pieces no fenders you can do floors jambs trunk anyinterior yesturday I blasted out my trunk it was undercoated took about 2 hours of actual work you also need a wet dry vacume so you can suck up sand to reuse I blasted floors and interior cab in about 1 1/2 hours you do not stay in one area you move contineously you come back to a stubborn areas if you have email will send a couple before after pic let me know will tell you anything else you need jon