[rumpity_z28]

red65mustang

Its a coating made by PPG and other manufactures but I refer to ppg because thats what i work with.
Heres a link to it on there sight where you can read about it but basically its a phosphoric acid based coating

http://www.ppg.com/cr-refinish/phase...indProduct.asp

Basically after you clean the steal you coat it with this stuff and then you can store it until needed then just primer

Oh its called DX520

[red65mustang]

If you live in Arizona, DX520 might be enough. Here in "Balmy" Florida (90% humidity) it works for maybe a couple of days.

In fact, I remembered (that's amazing, for me to remember anything) and checked. The instructions do say: "coat with epoxy the same day".

PPG wants the epoxy on the bare steel immediately for a h2o/o2 barrier to stop new rust scale from starting.

.................................................. .................................................. .
Rumpity,

I hadn't gone back and read this whole thread again till now.

For me, it's got way to many tangents and other topics twisted into it.

Here's my answer for a temporary coating on a new rust free bare steel panel part:
I clean it with brake cleaner to remove the anti-oxidation oil coating, scrub it with a red scotch brite pad to remove any rust scale then spray it with a heavy coat of Duplicolor (green) Self Etching Primer from the local autoparts store.
That works for 3 months+ in Florida.
The etch primer is easy to sand off, it's compatible with epoxy/filler/etc.

Got rust, you have to absolutely remove it to use etch primer alone for 3 months storage.

[hemi43]

Excellent reading on epoxy primer. My question is about the metal prep you all use. It clearly states that you must rinse off the prep after working it into the metal, but my problem is that when I'm doing a large panel (like a fender), the panel gets flash rust instantly after rinsing, What's the secret?? I have tried Dupon't product, Por-15's as well as others, and I always have problems. Thanks. Dan

[red65mustang]

Question: I applied 1.0 mils of epoxy to the sanded bare steel.

What do you use to sand the epoxy to prep for the filler that won't scratch thru the epoxy?

I think the idea is great but how do you do it and make a mechanical bond of the filler to the epoxy.

[BarryK]

Originally posted by red65mustang
Question: I applied 1.0 mils of epoxy to the sanded bare steel.

What do you use to sand the epoxy to prep for the filler that won't scratch thru the epoxy?

I think the idea is great but how do you do it and make a mechanical bond of the filler to the epoxy.

************************************************
Epoxies in the "automotive aftermarket" are all made to have a 7-day open coat. What that means is the epoxy can have any primer, paint, clear or body filler applied with out sanding the epoxy first for the first seven days. (delayed cure)

After the epoxy sets for 7 days than you need to hand sand the spot that you are applying the filler to with 180 and just a scuffing up is needed.

The benefits:
Ever sand ten year old filler off and noticed the metal had rust?
Epoxy will adhere better to the epoxy than 24 grit grinding marks in bare metal.
The epoxy can increase the flexibility of the glazing putty or body filler by 50% and higher.
Of course when you air-file the body-filler you are going to break through to metal in areas and before going to 2K primer we spray one or two more coats over the whole car again or on panels we did body work.

The test!!! (65 I know you like tests!)
Here is a test for you!!!
Go to Home depot and get an 18 metal Gage panel they are about 18"x5".
On one side grind with 24 grit grinder.
On other side DA with 80 grit. On the 80 grit side spray two coats of epoxy and to be safe let panel set one day (24 hrs as not sure type epoxy your using and cure rate)
Next day with the same body filler mix enough to apply a normal coating on both sides of the panel (Do not sand the epoxy first), Not 1/2 inch thick but normal filling and try to get both sides as close to same in thickness as you can.
SET in corner for one week (no cheating) than bend panel back and forth:
Here is what will happen the filler on bare metal side will crack right away and some if not all, will fall of.

The filler over epoxy side will may not even crack or split. (If your using an automotive grade epoxy)

You will be graded on this.

[red65mustang]

I'm definitely not a chemistry professor, but the chemical stew your brewing is way to scary for me.

Your saying to apply a catalytic heat reaction polyester/MEK filler on top of an uncured still reacting epoxy( that the amines haven't finished cross linking the epoxy molecules on).

Nah, I'll pass on that idea, thanks for the how to.

Your sheet metal test would prove alot more if you imbedded a hook in the filler of each, hang it with rope. Add weights till one fails.

[BarryK]

Your sheet metal test would prove alot more if you imbedded a hook in the filler of each, hang it with rope. Add weights till one fails. [/B][/QUOTE]

*******************************************
That would be a good adhesion test but it would be pointless as we know both would have all the adhesion needed.

You don't wait a week to apply primer over your epoxy now, do you? Use as a sealer shops paint over epoxy in 30-60 minutes everyday.

More and more restorers and rod builders are putting there filler over the epoxy.

Not saying you should but the people on here should have all the information they can to better themselves and the jobs they are doing.
I'm not brewing nothing, as the 7 day open coat has been an auto refinish market standard for years. (see tech sheets)

[red65mustang]

No I don't know (or agree) that filler applied to smooth uncured epoxy has even nearly as much mechanical adhesion as to sanded steel. The polyester makes no chemical bond to the epoxy, what's glueing the filler on?

Epoxy and polyester/MEK is a totally different chemistry than epoxy and 2k primer during the open coat window.

I'm not saying it doesn't work, just wondering how well.

Like they say "it's your car, do whatever the #### you want.

I'm done on this topic.

[BarryK]

Thats OK,

I knew when I wrote what I did that a few things would happen!

1) There are probably 15-20 people on here that will do the panel test as there are about that many that really want to know and want do the best they can. They will report, I'm sure.

2) I knew some old timers would slam me that they did it this way for 60 years and body filler never fell off!

I agree with you!
Its your car and you can do what you want!

[firstgenbird]

PPG specifies that their body filler may be applied over top of DP or DPLF epoxy. Epoxy is also compatible as a top coat over their filler.

http://www.ppg.com/refinishftpsite/d...filler_pix.pdf

I hope someone tries Barry's test and reports back so we know which order is strongest.

[BarryK]

Originally posted by firstgenbird
PPG specifies that their body filler may be applied over top of DP or DPLF epoxy. Epoxy is also compatible as a top coat over their filler.

http://www.ppg.com/refinishftpsite/d...filler_pix.pdf

I hope someone tries Barry's test and reports back so we know which order is strongest.

******************************************
Here is how epoxy got into the auto aftermarket paint industry.

Around 1970 Mercedes went to "Glasurit" (way before BASF bought them) their paint supplier along with Hubert's paint. Code 735G means painted at factory with Glasurit. Code 735H means painted with Hubert's.
For warranty work they wanted a coating for underneath the filler.
Glasurit than introduced the epoxy to this market and it has been a requirement for Mercedes and Porches warranty work every since. Now 6 months ago Toyota requires epoxy to be used under all filler for warranty work.

[red65mustang]

Very interesting info from PPG

Hope somebody does my "weights test" and reports back. That's what you really need to know.

Any filler tech rep's reading this thread?

[390xw]

Hi guys
I would have said the same as martinsr
when i did my learning in a government workshop they failed us for usin anything on a bare panel before aplyin the filller as we were told it wouldnt stick properly and that is how its been done werever ive worked for years then the etch would go on then a highbuil primerfiller and that would be it befors the jam job anyway thats my knoledge on it have a good day.

[red65mustang]

Thought up an easy "real world" test for you to prove epoxy/filler is better than sanded steel/filler.

Make 2 steel mudflaps, do one with, one without, post the results on your web site after ? miles.

That's what I'm looking for, better impact resistance, gladly put a skim coat of filler on the epoxy on the front valance, lower rear qtrs, etc.

[jcclark]

These "tests" to see which is stronger is a moot point.
Maybe bondo over primer is stronger, so what!.
It's an extra step, For why? Putting it on over bare metal
properly prepared it will be strong enough to outlast the car.
I don't really care if someone comes out with something
stronger. As far as these tests are concerned that's not
proof either, just because it bonds better now doesn't
mean it will bond better 5 years from now, it may not.
If anmyone out there is having adhesion problems
with filler you're doing it wrong.
For me I'll stay with what's proven, especially since it's
quicker and easier.