Phosphoric Acid Metal Prep

[kyteler]

PPE is your friend. 

[Toddy415]

I cleaned mine up with meths as per instructions then wax and grease remover then applied epoxy primer. The epoxy is super easy to chip off / hasn't stuck very well at all so I am thinking I went wrong using the meths. I will try cleaning up using thinners instead next time.

[Spencer]

Yeah something went wrong, 2 part epoxy will usually stick pretty good even to a poorly prepped surface.

So using the data sheet for something like the protec 408 epoxy primer it says to sandblast your metal or sand it until clean and coat it. Says if you are using new sheet metal to use their acid wash (which is phosphoric acid) to remove the oils, read the data sheet for the acid wash it says to use steel wool to apply and wash with water so you are washing and scouring it, then wax and grease before painting. This is how I learnt from a couple restoration body work guys, backed up by the data sheets of most paint systems. Now epoxy is used as a sealer of old paint so it does stick to other shit and usually well. But you want to test it out and if you go all the way to bare metal I don't see why you would want anything else under it, especially a rust converter primer, they don't have the same adhesion as magic chemically cured 2 part epoxies.

http://www.ppglic.com.au/uploads/tds/408 Epotec Epoxy Primer (2).pdf

So for all applications its pretty much clean white sanded/scotch brite steel clean with wax and grease and then apply 2 part epoxy. If you have pitting or want to clean it then acid wash with phosphoric, neutralise with water. I would still key the metal up again with scotch brite after the acid wash to remove everything as you can get some residue if the acid wash got dry. Anything else is garbage IMO.

Then for safety as said modern epoxy cures with polyamide, old school ones used amine or something toxic (not a chemist). So 2 part epoxy is very similar as other single stage paints as far as safety goes, ie don't breath it and avoid getting it on the skin and eyes. It doesn't have the extra death factor of polyurethane which cure with isocyanate, anyone who has sprayed urethane clear knows how deadly that shit smells.

[dmulally]

On 13/08/2019 at 12:14, Toddy415 said:

I cleaned mine up with meths as per instructions then wax and grease remover then applied epoxy primer. The epoxy is super easy to chip off / hasn't stuck very well at all so I am thinking I went wrong using the meths. I will try cleaning up using thinners instead next time.

Sounds like it needed a bit of scuffing first. 

[Lord Gruntfuttock]

Seems strange. I've thrown Durepox onto greasy, shiny, and rusty old bits when emptying/cleaning gun out, and it has stuck fast every time...

[Toddy415]

31 minutes ago, Lord Gruntfuttock said:

Seems strange. I've thrown Durepox onto greasy, shiny, and rusty old bits when emptying/cleaning gun out, and it has stuck fast every time...

Thats what I was expecting i might have to do test bits to find out whats wrong a bit annoying but better to find it now i guess. Im guessing its user error not a product issue. 

[Spencer]

The test is when you sand it back, have had epoxy stick not so well to a bunch of things when you start sanding.

When block sanding you will go through your epoxy and/or high build primer and that is the real test, if you have some shit adhesion at the base layer (like some shit single stage rust primer or badly prepped steel) the edges don't feather and things come off in little clumps leaving sharp edges, just making more work by needing filler etc to fix it. Then in the back of your mind for the next 10 years that your paint job is stuck on real shit. You get away with it on internal fix ups where you just poo it on and walk away, it sticks so well to itself that it doesn't go anywhere.

[Mr Vapour]

all good interesting stuff. I support reading tech sheets. best way to get things prepped correctly. 

I'm not far away from engaging a repair cert inspector so will see what processes he wants me to use. he has told me to not even blast till he sees the car. 

When requested I supply a phosphorous wash tergophos and the coating epiphos (same as keyphos253) I have the epiphos in 20ltrs so if any one wants some let me know. 

 

[ajg193]

Bit off track but:

http://www.emdocs.net/hydrofluoric-acid-burn-keeps-burning/

 

Some rust converters can have HF in them (case study in the link), so be sure to read any datasheets/warnings on the bottle or it could well kill you

[dabuzz]

Slightly off track, but in keeping with the 'prep' theme.

When you have panels acid dipped, they coat it in some stuff that looks kinda black to stop flash rusting, and can store in for ages.

does that have to be fully washed off, or just scuffed up and epoxyed over?

[Spencer]

I would scotch brite it with wax and grease at a minimum, see what happens. Or spray a patch then sand it back to test.

[yetchh]

23 hours ago, ajg193 said:

Bit off track but:

http://www.emdocs.net/hydrofluoric-acid-burn-keeps-burning/

 

Some rust converters can have HF in them (case study in the link), so be sure to read any datasheets/warnings on the bottle or it could well kill you

 

I don't think I've seen any converters with hyroflouric in them, they've all been phosphoric.. That shit is lethal anyway, you need an antidote if you (for some fucked up reason) want to use it.. 

[ajg193]

Just now, yetchh said:

 

I don't think I've seen any converters with hyroflouric in them, they've all been phosphoric.. That shit is lethal anyway, you need an antidote if you (for some fucked up reason) want to use it.. 

I think it is more for cleaning stainless when welding

[yetchh]

We used it for cleaning old buildings back in the UK.. Stinky shit, special with no mask. 

[RUNAMUCK]

I have heard a mate say they weren't allowed to use some stainless steel cleaner at his work anymore. (He's a TIG welder)  perhaps that had that shit in it?

I also saw a tech bulletin at a brake shop once saying that certain kinda of brake stuff will convert into that if the car has been burned out. And it will keen burning you in till you get an injection to reverse it. 

[Lord Gruntfuttock]

Yeah think some o-rings produce it if burned too...

[SR ROLLA]

Thanks for the input everyone. It's awesome how much knowledge and experience gets shared around on oldschool.

Cheers

[Murph]

Why add zinc to phosphoric acid?

[87creepin]

On 13/11/2022 at 16:02, Murph said:

Why add zinc to phosphoric acid?

Extra rust protection I believe. And zinc phosphate is a sweet coating. 

/broscience 

[ThePog]

Ah man I have a 20l of 99% phosphoric somewhere that i inherited when I bought a business, I moved it when tidying up my container in the pandemic and it had a small crack in the container. This was enough to react with the wooden floor and set the container on fire. It sat outside til I could wash the container floor and find a new container, and where it sat and leaked a bit more the ground bulged up around it. How I didnt get any on me is miraculous.

I have no fucking idea what to do with it..