SPI epoxy primer after panel treated with phosphoric acid

borna428

Promoted Users
Hello all,
I put a new floor panel on my restoration project. initially i was thinking to use mastercoat series moisture cure urethan to seal the pan. as part of the steps, the panel had to be treated with their rust converter which has some degreaser and phosphoric acid in it. I treated the panel with their rust converter which has the phosphoric acid in it. but now I changed my mined and want to use the SPI epoxy primer on the panel instead of their urethan moisture cured paint.
I have heard SPI epoxy primer is not going to work if applied on phosphoric acid treated metals. So the question is am I too late to go with SPI epoxy primer? I have already ordered 2 quarts and don't want to change to another brand.
what do you guys suggest me to do to neutralize it ? Should I rewet it with the same solution, wait a few mins and rinse it off with ammonia and then water? will that work?

the data sheet for the metal perp says "Mastercoat Metal Prep & Rust Remover can be neutralized with water in the event of an accident."


Thanks
 
Get some Ospho and follow the procedure on page 13 of the SPI tech manual. The only difference I would add is to use red scotchbrite pads with the Ospho, not a towel. A thorough running water rinse is critical to removing all traces of acid film. Clean with SPI #700 and let dry before primer.
 
Get some Ospho and follow the procedure on page 13 of the SPI tech manual. The only difference I would add is to use red scotchbrite pads with the Ospho, not a towel. A thorough running water rinse is critical to removing all traces of acid film. Clean with SPI #700 and let dry before primer.
Thanks for the info. but the panel is already treated with their version of rust converter which has phosphoric acid in it. So what you are saying is that I should re-wet it Ospho and neutralize it based on the tech note, even though I didn't use Ospho ?
 
The Ospho will remove the stuff you have already done. The point is to remove the product that is not tested to work with SPI. Do not use any products from this point other than those listed in the Tech Manual.
 
The Ospho will remove the stuff you have already done. The point is to remove the product that is not tested to work with SPI. Do not use any products from this point other than those listed in the Tech Manual.
Absolutely. I switched after I read so many good thing about SPI. So another question is how can I confirm that the acid is completely neutralized? Instead maybe I can do a proof of concept on a piece of metal that I don't need. I will apply the rust converter as I did on the panel and let it dry. Then will neutralize it with the procedure in the tech note and spray the epoxy primer. what kind of behavior I should see if the test panel is not neutralize correctly? Is it something I can validate after the epoxy is dried or will not show until months later?
 
we went to the local Mika place and they had a rust solution called Rust Raider. They are mostly the same materials with phosphoric acid and put a real nice blue coating on the part after all the rinsing. That blue coating is what I am used to seeing from a good iron phosphate with the good old molybdate mixed in it. But bottom line, just dont come back posting about the SPI epoxy not sticking to the other product even after you used the ospho, what starts on the base metal is what you are trusting the SPI to stick to.
 
Absolutely. I switched after I read so many good thing about SPI. So another question is how can I confirm that the acid is completely neutralized? Instead maybe I can do a proof of concept on a piece of metal that I don't need. I will apply the rust converter as I did on the panel and let it dry. Then will neutralize it with the procedure in the tech note and spray the epoxy primer. what kind of behavior I should see if the test panel is not neutralize correctly? Is it something I can validate after the epoxy is dried or will not show until months later?
It's difficult to determine when the acid is neutralized. That's why acid treatments are dicey for the hobbyist. That's also why copious amounts of fresh water are called for on the rinse. A test panel is a great idea!
 
P. S. Want is wanted is not so much to neutralize the acid, but to wash it away. True neutralization would involve more chemicals, and it's best to keep it simple.
 
I hate the neutralization but its just white powder that keeps building up. If you clean concrete with muriatic acid, the concrete being a base, neutralizes the muriatic. It cleans because the muriatic dissolves the base of concrete and stops eating it when it is neutralized. Steel does not neutralize phosphoric, it reacts to phosphoric, so the neutralization is the water with ph or 7.

When you think you are done, most tell you to wait a couple hours before painting, if the white film does not return after two hours, its done. It is really tedious if you just hate to be pouring all that water back onto a cavity, like a drip rail, after you just did this because the water got in and rusted the panel out. I just used the kimberly clark blue, red, white shop towels, since they do not have lint like the generic or scott brand so I dont use copious amounts of water and being an industrial first guy, respect the phosphate coating it is leaving behind..

The mastercoat looks interesting though, noticed some ceramic paint on the site to try on my next set of headers.
 
I hate the neutralization but its just white powder that keeps building up. If you clean concrete with muriatic acid, the concrete being a base, neutralizes the muriatic. It cleans because the muriatic dissolves the base of concrete and stops eating it when it is neutralized. Steel does not neutralize phosphoric, it reacts to phosphoric, so the neutralization is the water with ph or 7.
Now couple of question. I am not in a position to bring the frame out of the garage to hose it down with water.
Does re-wetting it with Ospho and wipe it out with a wet rag and remove the water with wet-vac and repeat the process works as well?
Also how about adding some ammonia to the water in order to increase the PH and do the final wipe with plane water?
Last but not least, what if the white film does com back, at that point your still need to re-wet it with Ospho or just wash it with more water?
 
The main cause of failure of epoxy on acid treated metal is incomplete removal of the acid. If you want to deviate from the recommended procedure, you are pretty much on your own. I would not use ammonia. Use SPI #700.
 
The main cause of failure of epoxy on acid treated metal is incomplete removal of the acid. If you want to deviate from the recommended procedure, you are pretty much on your own. I would not use ammonia. Use SPI #700.
Can the Litmus paper helps to find out how well the acid is removed? I never do anything on my own and try to deviate from the recommended procedure for the product. The reason I am in this mess is because originally I wanted to used some other product and followed their procedure, but now I am switching to SPI epoxy primer.
One question that hasn't been answered. Once I done with all the cleaning and spray the primer. what kind of testing can I do to make sure adhesion and bonding of the epoxy to metal is good and solid?
 
Now couple of question. I am not in a position to bring the frame out of the garage to hose it down with water.
Does re-wetting it with Ospho and wipe it out with a wet rag and remove the water with wet-vac and repeat the process works as well?
Also how about adding some ammonia to the water in order to increase the PH and do the final wipe with plane water?
Last but not least, what if the white film does com back, at that point your still need to re-wet it with Ospho or just wash it with more water?

That is why I said I did not hose it down, just keep rinsing out a rag and wiping it off with clean water, hence the disposable towels. It is something you really need to experience your self. If you keep using the Ospho, you are just going to get more white film. The suggestion to wipe it off with Ospho is if you are past a simple white dust and have a white film that will not rinse any more. You can apply the ospho in 10 minutes, you can wipe it off for two hours to get no more white haze. I have diluted the ospho greatly, like a pint in a gallon bucket and went back over with the rag, it was strong enough to break the film but not aggressive enough to start more. At any point, if the rust still looks like rust, not blueish black, then you need to keep putting full strength on.

I would say definte no to the ammonia since you are trying to create an actual coating on the part. Ammonia will not kill it, but more likely to remove the good the ospho is doing.
 
That is why I said I did not hose it down, just keep rinsing out a rag and wiping it off with clean water, hence the disposable towels. It is something you really need to experience your self. If you keep using the Ospho, you are just going to get more white film. The suggestion to wipe it off with Ospho is if you are past a simple white dust and have a white film that will not rinse any more. You can apply the ospho in 10 minutes, you can wipe it off for two hours to get no more white haze. I have diluted the ospho greatly, like a pint in a gallon bucket and went back over with the rag, it was strong enough to break the film but not aggressive enough to start more. At any point, if the rust still looks like rust, not blueish black, then you need to keep putting full strength on.

I would say definte no to the ammonia since you are trying to create an actual coating on the part. Ammonia will not kill it, but more likely to remove the good the ospho is doing.
Some other guy recommended wiping with simple green before the final rinse with water and WAX/grease remover and said never had any issues. Do you recommend that?
 
Failure to adequately rinse metal treatment products is the most common reason for subsequent coating failure. So take that for what it's worth. If you can't use running water, you should use lots of clean water from a large bucket, and lots of clean disposable wipes. The way to tell if the metal is clean is that it "sheets," that is, water will no longer bead up at all on the surface, but you won't be able to determine that very well with a wiping method.
 
Some other guy recommended wiping with simple green before the final rinse with water and WAX/grease remover and said never had any issues. Do you recommend that?
simple green is diluted hydrochloric acid with more additives, so you are back to lowering the PH getting farther away from neutral. Its made to remove oxides from metals. You need to understand, that you are getting an iron phosphate type coating from the ospho, which is an oxide. So adding anything not recommended by the maker of the product is probably doing more harm than good. When Dawn is suggested, it is not because it is soap, it is because it clings to the surface and takes longer for the water to evaporate, bonus is cleaning too. But soap is high ph, so getting back to neutral without evaporating quickly reduces any surface rust. You will start to see rusty water in a bucket, but it will continue to clear up. You will get rusty water if you just use your hands without gloves on.

I wont argue that simple green will help remove the white dust film quicker than just water, but like everything else, quality happens with time.
 
As far as I know, Simple Green has citric acid in it along with a PH buffer, but I am not a chemist. I do know that I have never seen it recommended in a tech sheet for metal preparation prior to refinishing. It is a pretty decent first step to re-painting an existing finish, though.
 
I have found when I thought all acid was gone, a quick check with a wire wheel in a drill across the surface was shooting up fine white dust. This was residue I thought was gone. I use this across all surfaces and then scuff with 80 as the wire wheel tends to smooth out the surface.
This can be a final test when you think you are finished.

Here's an excellent video showing what happens if not removed properly.
He talks about the steps taken on the panels that worked well also.

 
Good video. Only comment is that the "fish eyes" were in fact craters from too heavy of application. He was correct that they posed no problems with adhesion.
 
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