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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Body - Exterior> The Ospho Solution..(rust removal)
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Topic Review (Newest First)
Today 06:40 AM
roger1
Quote:
Originally Posted by deadbodyman View Post
absolutely.
Shows again how you don't know.

The factory uses electrostatic primer.
Today 06:37 AM
Chevymon It sounds like you are giving advice for a collision shop job that only needs to last a couple of years, and if Barry printed your advice on the tech sheet, he would sell a lot more shops on his epoxy.

For maximum adhesion, reduced epoxy shouldn't be used on bare metal, and 80 grit DA scratches are easily covered with SPI epoxy.

I think you know better than what you are posting here, so I don't want to waste any more time on this.
Today 06:36 AM
roger1
Quote:
Originally Posted by deadbodyman View Post
also true,thats what the instructions on the can says....the instructions also "used" to say DONT use acid products on the metal (the main reason I started this thread) Think about it......lets say I have a brand new after market hood with that crappy black primer on it,its so thin it sands right off with 320.should I sand it of with 80 and scratch the heck out of it and put 80 scratches in it that will just have to be filled AND sanded again? NO,absolutely NOT ,I sand that primer off with 320 and spray my SPI epoxy reduced like a sealer then go right to paint.why make all that extra work when you don't need too. remember your filler lessons "if theres no sand scratches to begin with" theres no scratches that'll comeback in the paint.NEVER rely on the primer to do your filling for you.....
Also remember media blasting is NOT a good idea if the car is not completely takin apart...and not every car is a long term resto ,some are only in the shop a couple days.
This post just shows that your really don't know very much about basic prep procedures. Sanding metal with 80 grit does not "scratch the heck out of it". Two coats of SPI epoxy primer and the scratches in the metal are covered. I guess you've never done it or you wouldn't have said what you did. With conviction too.

It has bothered me from the near the very start of this thread that you push yourself as an expert with procedures that are so far off from what is accepted practice. This thread should have been closed long ago.

Not that I care what you do and what you push. It's the unsuspecting novice hobbyist that reads your stuff that I'm concerned about.
Today 05:57 AM
deadbodyman
Quote:
Originally Posted by roger1 View Post
The instructions for SPI epoxy are clear.
Sand metal with a D/A and 80 grit.

Where I can't get to with a D/A, I think the finish that a media blast leaves is good too. I use Black Diamond media.
also true,thats what the instructions on the can says....the instructions also "used" to say DONT use acid products on the metal (the main reason I started this thread) Think about it......lets say I have a brand new after market hood with that crappy black primer on it,its so thin it sands right off with 320.should I sand it of with 80 and scratch the heck out of it and put 80 scratches in it that will just have to be filled AND sanded again? NO,absolutely NOT ,I sand that primer off with 320 and spray my SPI epoxy reduced like a sealer then go right to paint.why make all that extra work when you don't need too. remember your filler lessons "if theres no sand scratches to begin with" theres no scratches that'll comeback in the paint.NEVER rely on the primer to do your filling for you.....
Also remember media blasting is NOT a good idea if the car is not completely takin apart...and not every car is a long term resto ,some are only in the shop a couple days.
Today 05:41 AM
deadbodyman
Quote:
Originally Posted by 67Elcamino View Post
DeadBodyman, My concern now if how I can get rid of the minor black freckles left on the paint. I was hoping that these spots, which were there before the ospho treatment, were already there. Theyre a PITA to take off and was hoping I didnt have to grind them off the entire car?

Any opinion on this? Im I over thinking this?
you mean the black freckles on the metal? right? I've run into this many times when stripping old cars and theres many opinions on the cause ..I believe they are caused by water getting in the system while priming,many shops and DIY's pay little attention to a good clean,dry air supply during the body work and priming process..I've actually seen this at a few shops I've worked at where there is so much water in the air its like a pressure washer,most bodymen will just let the air run until the water stops coming out of the hose and then prime but if you were to hold the blower up to glass you see the water is still in there. so much for the cause ....as for the cure?
I wouldn't loose to much sleep with those freckles ...
usually two applications of Ospho ,scrubbed in with a red scotch brite does pretty good then when you sand it all that's left is basicly a stain that can be primed,trying to chase all those freckles down is a losing battle ,I've never had them come back or cause any problems in the paint later on...
Today 05:20 AM
deadbodyman
Quote:
Originally Posted by roger1 View Post
The factory sprays epoxy???
absolutely.
Yesterday 09:45 AM
roger1 The instructions for SPI epoxy are clear.
Sand metal with a D/A and 80 grit.

Where I can't get to with a D/A, I think the finish that a media blast leaves is good too. I use Black Diamond media.
Yesterday 08:11 AM
Chevymon Mike, you have given a lot of good information here, but I just don't agree with what you are saying, and I use SPI also. BTW, Its hard for us--at home--to match what the factory was doing with primer 60 years ago.
Yesterday 06:46 AM
roger1
Quote:
Originally Posted by deadbodyman View Post
When the factory sprays epoxy the metal is NOT sanded...
The factory sprays epoxy???
Yesterday 06:24 AM
deadbodyman When the factory sprays epoxy the metal is NOT sanded...I don't know about other epoxies ,I only use SPI ,its been so long now I don't remember using anything else since DP-40... IMO most epoxies are about useless PPG hasn't had a good epoxy primer since DP-40 even then,as good as it was, it sanded like a rock,the only way to sand it was with 80 grit...It's also a good idea to check your adheasion before starting your filler work .I do this with a razor scraper and try scraping the epoxy off the metal but in most cases the average guy can test adheasion by sanding the epoxy down to the metal with 180 and feathering the epoxy back to make sure it feathers back nicely with no broken edges....
04-25-2015 07:28 PM
Chevymon pugsy is totally right on that. I use a hand held brush, like a tooth brush but it needs to be stainless steel. It doesn't throw the acid all over the place, and you don't have to reapply as often. Just like he said, you have to keep after it until its just shiny white metal when reapplying. If you get a sludge, that has to all come off while the sludge is dissolved.

Mike, I'm sure you know, but for those that don't---- as far as I know all the epoxy manufacturers require an 80 grit DA scratch on bare metal, although PPG is OK with 180 scratch when using their metal prep with zinc phosphate in it.

Tamco paint makes an epoxy---similar to what boeing uses---that can go over anything, even if its unsanded, but they still recommend sanding when ever possible. And they claim to be the only one available to the public with that option. I have used it and it works.
04-25-2015 05:06 PM
123pugsy
Quote:
Originally Posted by 67Elcamino View Post
DeadBodyman, My concern now if how I can get rid of the minor black freckles left on the paint. I was hoping that these spots, which were there before the ospho treatment, were already there. Theyre a PITA to take off and was hoping I didnt have to grind them off the entire car?

Any opinion on this? Im I over thinking this?
The black freckles are converted rust. That is if you used acid on it. Under the black will be nice brown rust ready to cause paint failure.
I've used a rust convertor which is basically the same as Ospho. The instructions state that the black converted rust is ready for primer and paint but it's a bunch of bull.

I ended up using a small spot blaster to get into the pits.
A wire wheel in a grinder or drill may sometimes get it all out.
Apply more acid and if it turns black, you're not finished yet.
Eventually, the acid won't turn anything black anymore and you've got all the rust out.
04-25-2015 11:28 AM
67Elcamino DeadBodyman, My concern now if how I can get rid of the minor black freckles left on the paint. I was hoping that these spots, which were there before the ospho treatment, were already there. Theyre a PITA to take off and was hoping I didnt have to grind them off the entire car?

Any opinion on this? Im I over thinking this?
04-24-2015 02:58 PM
deadbodyman yes, sometimes I do ,sometimes just 80. I tend to work through the grits when prepping bare metal. once it starts shining and getting super clean I have a hard time stopping But I use epoxy for everything, over my filler work and as a sealer when I need one.its a self etching primer too, so it sticks great to unsanded metal as well .theres really no need for any other primers ,SPI epoxy is all I use 95% of the time
04-24-2015 11:03 AM
Chevymon
Quote:
Originally Posted by deadbodyman View Post
I prefer sanding it off ,starting with 80 then 180 and finally 320 all dry sanded with a DA..
I've had great success with it for many years with no problems at all.....
Mike, are you spraying epoxy over 320 grit scratches on bare metal?
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