Ospho treated metal

Barryk;10209 said:
Exactly!!!
You must rinse with water before the Oshpo dries or it does no good.
You CANNOT sand the dried film off as metal is porous and it will in-bed in the metal.
May work if you do sand but very risky, only other way I know is sandbast with sand.

To spot test when done--let epoxy set 24 hours mix a 1" ball of filler and set in a couple of different spot over the epoxy, wait ten minutes and with a flat head screw driver try to pop off, if their is an acid film the filler will melt the epoxy and just fall off, epoxy although hard on top will never cure on bottom.
If you applied filler to an acid film metal it will do the same thing, harden outside but by the metal will still be gummy.
Click to expand...

I want to make sure I understand this correctly?
My imperial was sanded to bare metal a few years ago , then the metal was coated with an Ospho type acid treatment.
The metal now is actually quite rust free , but probably 60% of the car has a white ,rough type coating on it.
My plans were to sand this coating off to bare metal with 80 grit, clean with wax and grease remover then shoot a couple of wet coats of epoxy over the bare metal. Not to have anyone repeat themselves , but if I understand what is being said here I should reapply some sort of rust treatment to the metal first?
 
Yes.... You have to apply more treatment to remove what is on there!

Aaron
 
And rinse the acid off while it's still wet, an alcohol wipe down will also help it dry quicker to keep flash rusting to a minimum, then sand it with 80 grit and spray the epoxy.
 
I try and stay away from discussions on acid treatments, but there is one thing about Ospho in particular that concerns me. The marketing material for Ospho claims that it contains sodium dichromate, which is a hexavalent chromium compound. As such, it is carcinogenic via inhalation.

Given this fact, I would not sand a dried Ospho coating, nor would I treat a metal surface with Ospho with the goal of later sanding of the metal, even if the Ospho has been rinsed. I believe the chromate remains on the steel and will become airborne if sanded. Better to use a straight phosphoric acid product like PPG DX579 with a water rinse. Then sanding can be performed with less danger if desired.
 
thank you crash ! of course if you posted this elsewhere you would hear the 35 year pro explain in 12 paragraphs how wonderful and safe it is . i have used naval jelly all my life. great stuff but you keep it wet until rinse but i never used it to store a body bare. makes no sense to me anyway. if it's clean nothing can protect it better than epoxy. acid is one of the hardest things to use in our industry. just one mistake and your finished car has to be tore down and redone. those bubbles don't show up until it's finished and setting in the sun for a while.

and sadly yes you need to reactivate it to remove it. after that much time it could be neutralized from exposure but i wouldn't risk it .
 
To sum this up, acids do a real good job under controlled conditions and best example is a manufacturing line where they dip the fender in an acid and then the conveyor dips the finder in three to four rinse tanks and then it goes through a heater and dipped in the epoxy tank.==Perfection!

The problem is a body shop or a garage is not a controlled environment.

PPG and Dupont have acid washes and we have a lot of shops that do use them but they are smart enough to follow the directions to a tee and these products are made to be used under todays modern coatings.
The directions may say dilute with water, apply and rinse with water while wet, perfect, if done this way, it will do a very good job.
Short cut the directions and you will have a pack of problems.

Bottom line is acid must be neutralized or you are playing Russian roulette with you expensive paint job.

NOW for the bottom feeding companies that promote rust converters and acid apply and paint crap, all I can say is good luck and maybe this is why those companies target the non body shop painter, like the learning how or the do-it-yourself guys that don't know any better.
 
EXACTLY why they market to those guys. I've never seen a por-15 rep in my shop and never will...do they even have a sales rep? LOL. I can think of a few good reasons they dont, IF they dont.
 
there is nothing wrong with using acid to etch metal , there is also nothing wrong with using it to prevent surface rust on a sheet metal project. BUT you can not mix the 2 worlds. i have seen a 49 merc that was in bare metal for almost 5 years. during that time any rust prints got hit with naval jelly . when it came time for paint to start the car was soaked with a phosphoric acid mix and rinsed several times. this was done right.
unfortunately there are those who make outrageous claims on these forums that are backed up with nothing but more claims. i only believe half of what i see and nothing i hear . proof is in the pudding. i love learning anything new . prove me wrong and you've made my day by keeping me from screwing up. i damn sure aint perfect.
but down here we have a saying , " all hat , no cattle " .

and never use tech advice from anyone but the paint mfgr .
 
I wouldn't worry to much about blasting with sand. Grandfather was a big restorer in the 70's,80's,&90's. I currently own one of his cars he did in 84' that had everything sandblasted, DP40 PPG epoxy, and topcoated. I've been redoing pieces here and there as it was showing it's age as a driver but there is absolutely no rust on any of the chassis parts, aprons, or fenders I've redone. He has probably 8 more cars done at the same era that also show no rust on any of the pieces. Regular sand has always been his bread and butter. I've also repainted two other cars he did in the 80's and same deal. All he ever did was blast, air gun, and wipe down with dupont prepsol. I use coal slag now when I blast but occasionally still use sand. I do the hot dawn soap and powerwash method because it makes me feel better but over a dozen 30+ year restos holding strong evidence shows it isn't necessary.
 
The origin and treatment of the sand may affect results. I could see where some sands might have a high sodium content which would be pretty bad for steel.
 
I've had sandblasted parts sitting in the shop for close to a year with absolutely no surface rust even showing...other than where they may have been handled for moving. Dont ask why they are still sitting there with no epoxy on them. LOL. When we were using sand for blasting, we only used the extra-fine blasting sand provided from the local (right down the road) concrete facility. No longer using sand due to the dhec laws being put in place(not to mention the health hazards) ....trying to pass laws that say if you have a bag of sand laying in your shop its $1,000 a bag fine, unless you are certified to use sand. We are the only shop in the surrounding area certified to use sand for open area blasting...You are fine if it is contained in a containment booth..but the way they talk with new laws it wouldn't be that way soon...so we just quit. Got tired of spending the money, once you fix something they come at you with something else. We Use extra fine black beauty and crushed glass now.

Honestly never even heard of the potential rust problems by using sand until shine started mentioning it. Certainly didn't hear it from our media suppliers. I'll take his word for it, since we dont use the stuff anymore and he definitely has the more experience in that field. But personaly havent seen any adverse affects directly dealing with the use of sand for blasting. Who cares now though....combine those statements with the added health risks from using sand....its pretty much a no brainer not to use it. Live and learn.
 
it was explained to me by the media supplier who had at least 75 samples of media in bottles. bottom line was he had no control over what the sand was or contained. he explained how most of it would contain caustic salts and such. i'll take his word for it that sand is the last thing i wanted to use in refinishing. better, safer cleaner medias available. use what you like i'll shut up now.
 
That makes some sense to me. All the blasting sand around me is Michigan sand from the big lakes. This sand might be a low mineral content which might be whey we never had trouble with it.

When I lead I use a baking soda and water mix to remove the acids from the fluxing process. I wash the fluxed surface and then I rewash the lead repair with baking soda followed by simple green spray washed up with Dawn and rinsed really good. I used to have some trouble before I washed the fluxed area. Some of that acid would be on the flux surface and the lead would bury the contaminated surface. You know what happens in 6mos with trapped acid.
 
I find it interesting shine.. I've sen some issues at pinch welds on sand blasted pieces before, so wouldn't mind something else..
I don't know of any other media supplier around here though.
 
Chad, Menards carries a black beauty type blasting media that is slag of some sort. I use it a lot. Seems like it's 6 bucks a 50lbs bag. I buy sand for 6 bucks a 100 lbs. It's aggressive, costs more than sand, but cuts faster. Tractor supply carries a media that is similar but the one around me never carries the right grit so I go to Menards. I'd buy the 50 pounders for twice as much just because I don't like lugging 100 pound bags out back to blast.
 
Only thing i dont like about BB is the coarsness. Even the extra fine is just too coarse for sheetmetal IMO. Its great for frames and underbodys as it will remove just about anything it hits. We only use recycled crushed glass on exterior sheetmetal parts. If there is a real rusty area we will spot with the bb. The glass is just about the best i've found that gives you the same clean white metal that extra fine sand will give you. Might not be the "quickest" media....but quickness is not at the top of my list when it comes to blasting.
 
The black blast isn't bad, but because it is so coarse, it doesn't do a great job of removing rust pitting. Takes a while blasting the same area before enough of the smaller pieces in the mix remove the pits.
 
would blasting with fine grit crushed glass take the ospho off as well? will it create any rust problems later on like using regular sand?
 
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