Primer woe's

Maxrate · #1 05-23-2010, 04:43 PM

I thought I would fess up to a real blunder in hopes of saving my fellow builder some time and heartache.

I had some extra PPG Aluminum cleaner and conditioner laying around sooooo I thought, why not use it to clean up the parts before I lay down my coat of primer. There is only one problem, Im using Sherwin-Williams etch primer for all the internal parts. Without even thinking about it I cleaned up all the parts with red scotchbrite and the aluminum cleaner, which come to find out is really acid etch. After priming the parts and allowing it to dry over night, here are the results.

Comes right off with your finger nail..

The tech rep at SW gave me a fix of a different primer. But the old adage of never mixing brands and materials sometimes can be a costly lesson..

Auburntsts · #2 05-23-2010, 05:23 PM

You may need to let the primer "cure" longer after painting. I've been using Stewart Systems water based primer and 24-hours after shooting it's very easy to scratch with just your finger nail, but a week later it becomes a lot tougher, and some days after that it's as hard as a rock and almost unscratchable. Your SW may be similar in that it just needs some more time.

Paul Thomas · #3 05-23-2010, 05:33 PM

I'm surprised you're having a problem with acid etch. Could anything else have affected your priming session?

dedgemon · #4 05-23-2010, 05:44 PM

let it cure for a week and see what you get.

Quote:

Originally Posted by Maxrate

I thought I would fess up to a real blunder in hopes of saving my fellow builder some time and heartache.

I had some extra PPG Aluminum cleaner and conditioner laying around sooooo I thought, why not use it to clean up the parts before I lay down my coat of primer. There is only one problem, Im using Sherwin-Williams etch primer for all the internal parts. Without even thinking about it I cleaned up all the parts with red scotchbrite and the aluminum cleaner, which come to find out is really acid etch. After priming the parts and allowing it to dry over night, here are the results.

Comes right off with your finger nail..

The tech rep at SW gave me a fix of a different primer. But the old adage of never mixing brands and materials sometimes can be a costly lesson..

Maxrate · #5 05-23-2010, 07:11 PM

I should have stated that all priming was completed on May 18th. I just got back in town yesterday and the primer was as easy to come off as it was after it had dried for 24 hrs. I have never worked with self etching primers and the SW tech rep explained to me that once aluminum has been coated with a traditional acid etch and then conditioned with an alodine, or aluminum conditioner that it will be virtually imposible for any etch primer to adhere the surface.

This individual was at the SW 800 line and seemed to be an expert on the Sherwin-Willams product line. His fix is a mid level epoxy primer that is used in their Genesis line of fleet paints. We'll see how this works out and I'll post some more pics when I can. After this experience though I would only recomend following the product application sheet for the respective brand of materials and NOT to mix them.

Maxrate · #6 05-30-2010, 11:54 AM

Here is an update on my primer issue. After stripping and cleaning all the parts I was able to finally get some time to reprime the parts. I followed Sherwin-Williams recomendation of using their two part epoxy primer and the results were great. Good adhesion and corrosion resistance, and a very tough finish for a primer.

Although this is in their Automotive finish line of primers/paints it has been used with great success on small general avation applications. SW has a line of paints specificly designed for the aerospace industry but the price has a large upward curve. The DTM Epoxy primer comes in three different colors, white, grey, and black. The product description sheet allows tinting 10% by volume so I decided to simulate the old military zinc-chromate color.( I have a custom swatch if anyone is interested in the color codes). The SW Genesis urethane topcoat should be a great combination for the south Texas elements.

Here are some pics.

PainterJohn · #7 05-30-2010, 12:03 PM

Since i wasnt there, i can only guess as to what is the real cause of your situation.. BUT.. I have seen this before.. Using Etch, Acids, Precleaners, and Even water.

Each time i have seen something like this its because the aluminum is still dirty. Wiping the chemicals (in this case your PPG products) on the surfaces is good, but you have to make sure you get all the streaks off.. If these parts were alodined you would have seen right away that dirt was still present in the form of black streaks in the nice yellow/bronze alodine.
I dont think it was your primer, or your cleaner that failed.. both did as designed.. just dont think ya got the surface clean.

In my opinion (and i have painted about 60 airplanes) Nothing beats Etch Alodine and Zinc Chromate primer.

Maxrate · #8 05-30-2010, 12:28 PM

John,

I agree with you on using Zinc-Chromate for aircraft finishes. I have some limited experience with zinc and a fair amount of experience with automotive paint applications. I am however priming in a residential garage and I don't want to expose my kids or the neighborhood to these harsh chemicals. I thus decided to use less intrusive products so my wife wouldn't park my things on the curb.

. My mistake here, I believe was trying to mix the two. I used etch/alodine to clean the parts but then made the mistake of using a wash primer/self etching over the now etched parts, thus no adhesive properties according to Sherwin-Williams.

The intent of this thread was to highlight my error so that no one else makes the same mistake if they use an etch primer. The whole experimental nature of building an airplane is a real learning process and in hind sight I would have used the two part epoxy primer followed by the topcoat for ease and expense. Of course I agree that the best corrosion resistance and duribality is zinc for aircraft applications.

PS I looked at your websight.......Beautiful work BRO..

L.Adamson · #9 05-30-2010, 12:45 PM

Quote:

Originally Posted by Maxrate

Although this is in their Automotive finish line of primers/paints it has been used with great success on small general avation applications. SW has a line of paints specificly designed for the aerospace industry but the price has a large upward curve.

SW Genesis paints have been used on many RV's around here. I painted mine three years ago with Genesis, and it's still just as tough, glossy & new looking, as then. It's cheaper than their "official" aircraft paint..........but not exactly cheap.......in the sense of the word.

L.Adamson --- RV6A

PainterJohn · #10 05-30-2010, 02:59 PM

yeah i totally understand keeping your stuff off the curb! lol! BWT Thanks for the kudos man!

Good luck with your paint job! If you need some help let me know.. Houston isnt that far from Austin ;-)

When you factor in the coverage Sherwin Williams JetGlo, it actually comes out cheaper than the automotive Genesis.

But if you want to really save a few bucks PPG makes a subline called "Shopline" that used to be called Omni. Its great stuff, I recently painted an RV8 with PPG Shopline. And Ill probably do the RV10 im currently working on with it. Its a great product line for tight budgets!