Technical An epoxy primer adhesion failure?

Well hopefully this is the only spot...

It was all sand blasted, and then blown off.

I wiped cab down with metal prep per primers manufacturer specs.

Then wax and grease remover, and surface wash until it would white rag.

The CAB was CLEAN!

There is a chance the surface wash hadn't flashed, but I doubt it. It would have had 30 minutes or more while I mixed paint.

I'm thinking 1 of 2 things happened.

Possibly got a dust of overspray on that area, when painting somewhere else?

Or maybe there was some sand blasting dust fell out from somewhere and settled there when I was rotating the cab on the rotisserie while painting it?

Any of you guys with more experience have any thoughts or can tell anything from the picture?

Also epoxy manufacturer said their prep wash wouldn't affect anything as long as dried, and that wipe occurred days before.

AND I should mention the filler was put on the day after priming, so it bonded well. When blocking I had a high spot, so I hammered it down and that's when I noticed I cracked the filler and the separation occurred.

 

Sand blasting and wax and grease remover don’t like each other
Metal prep? The acid cleaner used with epoxy?
What is the product name/part number

metal preps don’t like the sand blast texture either if memory serves me correct


Cleaners can not be effectively removed over sand blast.
One reason I always DA with 80 then epoxy

 

Ive seen epoxy turn loose if not cured enough before putting something over it.
24hrs should be enough if the temp is good

 

Why does sand blasting and wax and grease remover not like each other.

It was Kirkers DTM Prep, and Enduro Prime. Hesitant to throw their name out there, because I'm sure it wasn't a product issue.

 

I always read a tech sheet. What Ive learned is that sometimes they mention not be used over sandblasted metal.
The reason is the residue can’t be removed from the sandblast texture.
The texture holds or traps the cleaner.

 

Is the primer designed to go over a sandblasted surface? Is it polyester compatible?

 

Yes and Yes

 

Ive seen a couple epoxies that polyester products would soften them.
When reviewing product info I look for filler compatible.

 

This the product?
https://s3.amazonaws.com/cdn.autobodytoolmart.com/downloads/tech-sheets/KIRK-6860-TDS.pdf
says it can be used over blasted metal
To throughly neutralize the product.
Any further cleaning after this step shouldn’t be needed

 

Even if it softened it you wouldn't think it would be a clean flake like that... I mean literally none of the epoxy stuck. And there was plenty of tooth.

 

Yep

 

Their tech sheet on the wipe says it needs to be neutralized with water did you do that?

 

Sounds like unhappy chemicals

 

Or surface wash...

I went over it after it dried with wax and grease remover and then surface wash.

Like I said though, Kirkers tech guy said even if I didn't do that it shouldn't flake like this. Which lead me to believe it was dust.

 

I highly doubt that dust caused this. Looks like a compatibility issue. My money would be on wax and grease remover before neutralizing. Need super fast solvents when you sandblast like acetone.

 

What brand/number wax and grease remover?

 

Kirkers said it wouldn't matter whether wax and grease remover was used or surface wash was used to neutralize it.

I'll keep the acetone in mind. It's odd that I've done ultiple parts this way, and this is the only issue...exact same procedure.

 

Kirkers...it was all Kirker products.

 

Sounds like the Kirker guy is just making **** up as he goes along. If wax and grease remover is not on the TDS as a neutralizer there is a reason.

 

I went back through my posts...it was primed last October.

I actually did all the prep work the day before. So all the solvents should have had ample time to flash.

 

Also too, on the wax and grease remover did you immediately wipe it off with another rag in the other hand or did you just wipe it and let it dry?

I wipe it on with one hand and immediately wipe it off with a clean rag in the other hand following each other.

I have seen problems with people wiping it on and not coming behind and wiping away any residue but not quite to the extent of what you have.

I tend to agree that it looks like a chemical problem. Anything different on the actual part of the metal there ? Lead? Metal filler ? Etc?

.

 

And this is why slower solvents dont work well with sandblasting because they are hard to wipe off the rough surface

 

I didn't read everything. I'm just gonna throw some experience at this. ETCH 1 WAY OR ANOTHER. If you blast, clean the dust and you're done. No blast, just metal prep, you're done. Clean, sand, ETCH PRIME, you're done but most poly primers don't play well with all etch primers. Filler over epoxy. WHY!?! Filler needs the most bad*** MECHANICAL BOND you can give it, that includes over f'gl*** as well. A good tooth. All this extra preparation is of the "some's good, more's better" school. That school ****s. Pick 1, piling up preps is a fools errand, always has been. You were led astray by pamphlets and urban legends. Hey, you asked.

 

Completely go thru the steps you used.
What products and sequence before priming.

 

Was it a slow evaporating remover, or a fast one? I'm curious if the Kirker wax remover is silicone based or not?

 

I wipe with one rag and another behind it. It still has a moist look to it for awhile. If it's been DAd smooth then it wipes off with the second rag.

But even if it wasn't, would multiple wipe downs with the surface wash remove it?

Nothing else was used in this area.

 

Sandblasted
DTM Prep to prevent surface rust, let dry...
Wax and Grease Remover
Surface Wash

Set over night.

Primed next day.

Filler was 3 days later.

 

The wax and grease remover sounds suspect.
The metal preps I’ve used was done this way:
Apply metal prep per directions then neutralize.

 

I don't get the wax a grease remover step. You are adding another chemical before neutralizing. The reason you neutralize is so the acid doesn't react with something. You have added something for it to react to in the procedure that is not called for by the manufacturer.

 

It may be, I don't know, but Kirker repeatedly told me that once dry it didn't matter what the etch was wiped with. I will verify again Monday.

Is there àny chance that the chemical bond between the filler and epoxy is stronger than the bond of the mechanical bond between epoxy and metal? And when I flexed the metal at that curve from dollying it caused it to pop loose.

I mean I was hammering pretty good, I expected the filler to crack, just didn't expect the paint to turn loose.

I still find it odd, I've went through gallons of these chemicals and primers, and this is the only place this has happened.