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Old 04-15-2005, 06:08 PM
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Epoxy is a little weird acting.

A medium coat is bad news for adhesion,
One wet coat is good for adhesion and fair for corrosion protection.
Two wet coats, gives best adhesion and corrosion protection.

Three coats don't help or hurt a bit with a big NOTE that this is only true if good flash times were given especially between the second and third coat.

In other words three coats back to back is a disaster waiting to happen.

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Old 04-15-2005, 07:03 PM
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Okay, I think I got it.
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Old 04-15-2005, 09:21 PM
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Perhaps it's because this is April 15 (tax day) that I'm inclined to make this comment, but in reading over this thread I can't help but reflect on the role that VOC regulations play in all of the adhesion issues discussed above. As a former epoxy primer formulator (non-automotive) I'd be willing to wager that if you were able to do an apples to apples comparison of current low VOC epoxy primers versus an old fashioned epoxy-polyamide based on solid epoxy resin (500 epoxide equivalent weight) and high equivalent weight polyamide, one would find the conventional solids product to be more forgiving of less than optimal surface preparation, provide better adhesion over a wide range of steel surface profiles, and be more tolerant of mix ratio inaccuracy.

I fully agree with the vast majority of BarryK's comments on this and other threads, but I have a difference of opinion regarding his comment about the role of cost-cutting versus VOC regulations when it pertains to epoxy primers. In my experience, deficiencies in the adhesion of high solids epoxies under practical field application conditions have a high probability of being related to the fact that they are formulated for low VOC, and a very low probability of being the result of raw material cost reduction activities. Give me an unrestricted choice of epoxy resin and curative (non-VOC regulated) any day, and I bet it will be more forgiving and better all-around performing than any low VOC epoxy.

(The above opinion is strictly my own, and not necessarily the opinion or policy of my employer.)
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Old 04-16-2005, 05:53 AM
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Quote:
Originally Posted by powderbill
Perhaps it's because this is April 15 (tax day) that I'm inclined to make this comment, but in reading over this thread I can't help but reflect on the role that VOC regulations play in all of the adhesion issues discussed above. As a former epoxy primer formulator (non-automotive) I'd be willing to wager that if you were able to do an apples to apples comparison of current low VOC epoxy primers versus an old fashioned epoxy-polyamide based on solid epoxy resin (500 epoxide equivalent weight) and high equivalent weight polyamide, one would find the conventional solids product to be more forgiving of less than optimal surface preparation, provide better adhesion over a wide range of steel surface profiles, and be more tolerant of mix ratio inaccuracy.
************************************************** **

1000% agree.
bwk

I fully agree with the vast majority of BarryK's comments on this and other threads, but I have a difference of opinion regarding his comment about the role of cost-cutting versus VOC regulations when it pertains to epoxy primers. In my experience, deficiencies in the adhesion of high solids epoxies under practical field application conditions have a high probability of being related to the fact that they are formulated for low VOC, and a very low probability of being the result of raw material cost reduction activities. Give me an unrestricted choice of epoxy resin and curative (non-VOC regulated) any day, and I bet it will be more forgiving and better all-around performing than any low VOC epoxy.

************************************************** *
True, but not half the problem.
These simple VOC changes when your dealing with a handful of different products besides epoxy are a total nightmare!
People don't have a clue of the cost involved.
Seems like everyday we get a letter saying this particular resin , pigment or solvent we are changing our spec from 3% to 5% (as an example)
The lab is spending hours of testing and cataloging each of these items so the finale product does not change or there is an adverse reaction.
Very expensive and time consuming.
bwk



(The above opinion is strictly my own, and not necessarily the opinion or policy of my employer.)
************************************************** ***
At least you can post! Good employer!

I know a lot of people and have a lot of friends that read on here with major companies that cannot post at all (under any name).
It is a firing offense!

I'm forever getting emails from them saying you should have said this and this!
I understand why their not allowed on here as anything that is said can be held against you for sure and it gets hard just to generalize sometimes with out hanging yourself.

I do know this, people on here would be shocked to know how many people read this that are not members and are pretty high up with some of these companies in the automotive paint field.
bwk
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Old 04-16-2005, 09:22 AM
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And I THANK ALL OF YOU !!!!!

It's really a blessing to be able to get the

"Straight story" of many of these confusing issues.

So many of us "Do it Yourselfer's are at the mercy of less than knowledgable paint suppliers or so called "pro's" who give us the wrong advice or product.
I was reading an article in a mag this morning on doing a rear quarter replacement and using the Por-15 for rust treatment. I believe this is a usefull product in some instances but a little more elbow grease and application of a better product will produce longer lasting protection.
I know this from the advice and knowledge recieved HERE.

AND, I learned something as well today. 180 IS fine for bare metal to apply epoxy over. I was alway's concerned that the 180 wouldn't provide a deep enough scratch for good adhesion. Thanks Bob.

I'm no expert by any means but I have done quite a bit of P&B which was learned the hard way by making mistakes and redoing my work due to inexperience and BAD ADVICE.

Thanks to EVERYBODY.
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Old 04-16-2005, 10:40 AM
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I'll second Bee4Me's thank you's. After an overnight dry time for my first coat of epoxy on some sections of bare metal and some sections of skim/fill, I sanded out my runs and shot a second coat over everything this morning. With my gun better adjusted the second coat looks much better - although it sounds like looks might be deceiving with epoxy. They don't tell you a lot about adhesion.

I've got the heat cranked up in the shop at the moment to get a little better "cure" and then it will be on to shooting some fill primer and working with the long board.

Anyhow, thanks for the advice. This thread was very timely for me.
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Old 04-16-2005, 03:28 PM
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Quote:
Originally Posted by Bee4Me
And I THANK ALL OF YOU !!!!!



AND, I learned something as well today. 180 IS fine for bare metal to apply epoxy over. I was always concerned that the 180 wouldn't provide a deep enough scratch for good adhesion. Thanks Bob.

Thanks to EVERYBODY.

Misunderstanding , some where.
On metal always use 80 grit. Some of the epoxies need more of a scratch to bit because of the VOC changes. Not all of them but better safe than sorry and don't worry about what you have done in the past a lot of these warnings started coming out about six or so months ago.
bwk
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Old 04-16-2005, 09:19 PM
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Quote:
80 grit followed by 180 for bare metal is best IMO, 80 grit alone is good enough if you end up with enough scratches.
This from early in this thread posted by badbob.

If I misunderstood this, I guess I'm STILL confused.Sort of.

80 is fine for me personally,as I said, I been doing it this way for several years now.
As we know 80 does require some filling with epoxy being "thin" anyway and on some parts I don't necessarly use 2 coats,my bad I suppose,but I'm just looking for a barrier not really filling which you almost have to do with 80.

This said, I was looking for a little less finishing work and I agree on the finer you can sand before applying any type paint/primer the better it will finish out and the less work you have.As long as you have GOOD adhesion.
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Old 04-17-2005, 02:04 PM
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Quote:
Originally Posted by Beenaway2long
Vince-
I'm starting down the same path as you. Just a question or two for you, though.

After the DX330, did you wash it off with thinner? That stuff seems to leave a residue even after you wipe it down 3x. I followed the tech sheet, and was not impressed.

Do you think there was a chemical reaction due to 2 different brands of paint? This stuff is getting rediculous. You need to be a Nuclear Chemist to paint a car. Just staying within the PPG line, there are like products you can't use over one another.
Well DX330 is NOT made to be a final prep, the flash point is to high in most cases. DO NOT use a thinner you could vary quickly wipe open a can of worms, instead DX320 would be a better choice for your final.

Rick

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Old 04-17-2005, 06:12 PM
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80 grit is rough, unless youll lay enough coats to fill in scratches (filling in with primer-filler) over epoxy
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Old 04-17-2005, 06:16 PM
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Quote:
Originally Posted by mitmaks
80 grit is rough, unless youll lay enough coats to fill in scratches (filling in with primer-filler) over epoxy
************************************************** *****
80 grit scratch with a DA over bare metal, one coat of epoxy will totally hid.

Not true with 80 over body filler or other paint.
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