Epoxy vs. Self etching primer?

stutt66 · 02-09-2017, 04:41 AM

I'm curious to know what the difference is between epoxy primer and self etching primer.
Also when working on a metal project how to determine which one is most appropriate for the job at hand.

962porsche · 02-09-2017, 06:00 AM

between the two there are not really any huge differences as to the jobs they do .
etch primers are real good for old rusted metals ( even when they have been stripped to clean metal ) as they do what the name states it does etches the metal .
the problem with many etch primers is you can not top coat them with polyester based products .
that would be body fillers and sprayables like spray fill primers ( like feather fill) but you can use many build primers over it .
the flip side is if they are well cured you can top coat with polyesters but the time before they are cured enough it's pretty pointless .

epoxy primers do not offer the same metal protection as a etch does as they do not etch anything .
it does offer about the same rust protection to clean metals along with good adhesion to aluminum and zinc plated metals . you can use epoxy under you body fillers and you can easily top coat it with polyester products offering lots more options of products to pick from .

evercoat did come out with there G2 line of spray fillers to go over etch primers . it doesn't have the build ( fill) capability of the older evercoat spray filler but it's build is kind of close to the older spray filler to make it work ok .

both etch and epoxy have there uses and many times on the same car we would end up using both for our needs of the repairs .
i tend to use epoxy more over newer panels zinc coated panels and aluminum then old rusted ones when i tend to use etch primers on .
on this 1969 camaro i'm restoring right now i did new QTR's new door skins new trunk lid so i primed them with one coat of epoxy then used a urethane build primer over it to give me a mil build to block out nice and flat .
for the nose as they are the original panels with lots of rust . i sand blasted the nose panels then did my body filler work then etch primed them with one coat of the etch primer then went over it with the urethane build primer . the reason is simple as they were rusted and even though i sandblasted the crap out of them i still wanted a etch product on then just in case i missed ant rust spot when blasting . remember all it takes is one pin point size rust spot and the rust will come back . the etch will eat into the rust and hold it out from coming back .

stutt66 · 02-09-2017, 07:10 AM

Thanks very informative!

dwiniger · 02-09-2017, 08:38 AM

I have used a system from PPG Paints on my bare, (non rusty), metal. The metal etch is a two part system. The metal etch is mixed, sprayed on and allowed to flash for about 30 minutes. The next stage is a two part epoxy "sealer" primer, that needs to be mixed, allowed to set up for 30 minutes, then sprayed over the fresh metal etch, with in an hour or so.... (it could be up to 12 hours, or 24, its been awhile since I read the directions closely).

These paints are expensive these days, but this will create a very tough surface that resists rust, chipping and scratching.

kevin930t · 02-09-2017, 10:08 AM

With the new primers today,its not necessarily to go from etch prime then to a epoxy prime,there are primers that do it all.You can use it as a etch or as a high fill depending on how much you reduce.

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962porsche · 02-09-2017, 10:18 AM

i'm not into using metal conditioners of any type !
i have seen to many fail years down the road forcing people to strip there cars back down to bare .
the question i always ask is if your metal is clean and rust free why would you want to just start adding more needless work and cost .

last year i got a guys GTV alfa in my shop he spent 3 years restoring the car and 3 years of use after it was all done .
he stopped by and showed me how the primer was flaking right off the metal with top coat and all .
you could take your finger nail and scratch the paint off .
he used a well known metal conditioner and knowing him by the book .
the paint manufacture came out to my shop and looked at the car said the same as i did it's the fault of the metal conditioner . the paint manufacture wouldn't warranty the job and after many calls to the well known conditioner manufacture with no replies back or any one even coming to look at the car the owner took the car all back apart sent it out to be sandblasted back down and started all over again .
was using a conditioner on good clean metal worth it ? IMO not just NO but hell NO !

many people for some reason think more must be better and it's not !
it's not a penis so more isn't better !
what you want to do is use a metal cleaner like glasurit's 360-4 it cleans the metal it doesn't try and condition the metal it doesn't coat it with some film or any thing . it's just like what is done when your car was made . they didn't try and condition the metal they just made sure it was clean . your undercoats are your rust protection and if you do the job right it's all you should need to protect the metal .
i'm not a fan of any product that needs what is called a induction time just to make the product work . in this day and age having to wait a half hour or more to use a product after you mix it is out dated technology .

kevin930t · 02-09-2017, 11:09 AM

Thats a terrible thing to have happen and would only wish that on my worst client,haha.I agree i would not use a conditioner.Who knows what happened there it sounds like the product was not mixed right,or out of date,could be the other 100 things that can go wrong.I can only go by what i have done personally and the products i use and the way i apply them.I stick with one product from my primers to my clears.That way there is no geuss work.I dont claim to know it all but i can honestly tell you that i believe in the products i use,and yes they maybe more expensive but i only want to paint the car once...

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962porsche · 02-09-2017, 12:50 PM

Quote:

Originally Posted by kevin930t

Thats a terrible thing to have happen and would only wish that on my worst client,haha.I agree i would not use a conditioner.Who knows what happened there it sounds like the product was not mixed right,or out of date,could be the other 100 things that can go wrong.I can only go by what i have done personally and the products i use and the way i apply them.I stick with one product from my primers to my clears.That way there is no geuss work.I dont claim to know it all but i can honestly tell you that i believe in the products i use,and yes they maybe more expensive but i only want to paint the car once...

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yes i totally agree !stick to one product line !
the poor guy with the alfa is just screwed . i know him pretty well and he definitely has OCD so i'm sure he did every step by the book plus the 1000's of calls he made to me asking me questions when he was doing the car i'm pretty dam sure it was not user failure .

kevin930t · 02-09-2017, 03:59 PM

I have seen plenty of cars that were poorly prepped,and itsmaybe the fact that they dont know what all is involved in painting a car,i think u said it there slightest inpurity thnat will effect the out come.When i media blast a car i still go over it with 80 to knock down the dust/dirt out of the pores out of the metal,as you know its all in our own control.I always do my own prepp work not leaving it to a helper

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kevin930t · 02-09-2017, 04:09 PM

Maybe you could pm me & tell me what product that was used on the alfa.

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962porsche · 02-09-2017, 04:40 PM

80 is a little coarse for things other then a spray filler type primer .
most epoxy and etch primers being sprayed as a adhesion coat along with most build primers want to go over a 180 grit so later on it won't shrink in later on see 80 grit marks .
but this is when reading the TDS comes into play on just what products your using .
but yes after blasting you really need to sand the substrate .
you shouldn't prime right over a sandblasted surface .

doesn't matter what conditioner he used .

kevin930t · 02-10-2017, 11:56 AM

I got it...I feel bad for your friend.That is a hard pill to swallow.The one hood thing about a mess is that you can always clean it up...Just glad its not my mess.Haha

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bpu699 · 02-11-2017, 11:26 AM

Quote:

Originally Posted by 962porsche

i'm not into using metal conditioners of any type !
i have seen to many fail years down the road forcing people to strip there cars back down to bare .
the question i always ask is if your metal is clean and rust free why would you want to just start adding more needless work and cost .

last year i got a guys GTV alfa in my shop he spent 3 years restoring the car and 3 years of use after it was all done .
he stopped by and showed me how the primer was flaking right off the metal with top coat and all .
you could take your finger nail and scratch the paint off .
he used a well known metal conditioner and knowing him by the book .
the paint manufacture came out to my shop and looked at the car said the same as i did it's the fault of the metal conditioner . the paint manufacture wouldn't warranty the job and after many calls to the well known conditioner manufacture with no replies back or any one even coming to look at the car the owner took the car all back apart sent it out to be sandblasted back down and started all over again .
was using a conditioner on good clean metal worth it ? IMO not just NO but hell NO !

many people for some reason think more must be better and it's not !
it's not a penis so more isn't better !
what you want to do is use a metal cleaner like glasurit's 360-4 it cleans the metal it doesn't try and condition the metal it doesn't coat it with some film or any thing . it's just like what is done when your car was made . they didn't try and condition the metal they just made sure it was clean . your undercoats are your rust protection and if you do the job right it's all you should need to protect the metal .
i'm not a fan of any product that needs what is called a induction time just to make the product work . in this day and age having to wait a half hour or more to use a product after you mix it is out dated technology .

Interesting...

So help me understand...

If you have sheet metal that had surface rust, you just sand it best you can and epoxy primer over it? Or, etch prime? Confused...

I started using metal conditioner because rust started bubbling through years later if I just sanded and epoxy primed, painted. Not sure it made a difference...

What's the best surface prep for superficial rust?

962porsche · 04:07 PM

no if you have rusted metal you remove the rust . there are a number of ways to do it like media blasting . the problem with rust is all it takes is one pin head size spot and it comes back so i tend to opt for using etch primer on blasted clean but once was rusted metal .
to use a conditioner on new (never rusted) metal is even more pointless you want to use a bare metal cleaner made for cleaning metals then i would opt for a epoxy primer .

i have found over the years and looking at peoples work they tend to over think and over use products with the thinking more must be better .

just sanding rust in most cases will not remove it your still left with rusted metal .
using a etch primer on just sanded metal will do little to nothing and the rust will come back in no time .