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  #1  
Old 05-25-2021, 01:28 PM
ravenstar ravenstar is offline
 
Join Date: May 2021
Location: New Hampshire
Posts: 15
Default Preparation for Priming

Hi everyone, after lurking for months, I'm hoping to begin my own RV-12is project very soon, and I've got many questions. To get the ball rolling, I'm trying to arrive at a decision on interior priming that I can live without second guessing myself for years. Before I start my build I thought I'd experiment with some primers on the practice toolbox kit I've built.

I'm very conflicted: I tend to feel like others who don't want to damage the protection of the alclad surface to add a different kind of protection (not to mention all the effort to thoroughly rough up each piece -- did I hear 200 hrs added build time?), but I also like the look of the primed surface and the possible corrosion benefits. So I tried something I haven't seen discussed here yet: I cleaned one surface with Dove soap and when that failed to prevent the water from beading, I used a cheap supermarket clone of Windex since it's what I had hanging around to clean the surface then one more wash with detergent. Then I primed it with SEM primer without doing the usual sanding.

I guess this was the first time I've used a decent primer as I was stunned by the toughness of the coating. 24 hours after two passes 10 minutes apart, rubbing the surface with a dull edge of a piece of metal didn't leave any noticeable mark.

So now I'm wondering just how important scuffing up the surface is to getting a good bond? Seems like cleaning was most important. And what about the simple household cleaner I used in the prep? I wasn't expecting it to be so simple or effective, so I started looking around and couldn't find any reliable information on whether it would have an adverse affect on the metal or paint.

Any thoughts about this prep process? I'd rather not prime than prime in a way that damages the surface, or is just wasted effort.

Many thanks!
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  #2  
Old 05-25-2021, 02:24 PM
wirejock's Avatar
wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 4,544
Default Surface prep

My opinion. Worth $.02

Search for Aluminum Oxide

I am in the full prep ball park.

A light scuff and clean shouldn't damage the Alclad. All you're trying to do is rough the surface and remove aluminum oxide. Water break free surface is the goal. Hydrophillic surface.
Back to Aluminum Oxide. That's the thin layer that effects adhesion. Its hydrophobic. Water beads.
Lots of opinions.
Most cleaning products won't remove it unless they have an acid. I prefer Bon Ami and scotchbrite. Clean and scuff at the same time. Dry. Shoot.

The other method is chemical removal. Alumiprep with scotchbrite will remove it and scuff the surface. I also use it on some parts.

SEM is self etch so it's going to chemically etch the surface to promote adhesion. Lots of builders love the stuff. No personal experience.

There are some products you wouldn't use without a very thorough rinse. Bleach for instance. Some window cleaners have ammonia or vinegar. Test.

Test your paint. Shoot several tokens. One control with no cleaning. The rest cleaned or scuffed or both with various methods. Cure. Appy a section of black Gorilla tape. Leave it a day or two then rip it off. Go with whichever works best.
__________________
Larry Larson
Estes Park, CO
wirejock at yahoo dot com
Donated 01/01/2021, plus a little extra.
RV-7A #73391, N511RV reserved (2,000+ hours)
Empennage, wings, fuse, finishing kit, now FWF
Disclaimer
I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #3  
Old 05-25-2021, 02:59 PM
arr arr is offline
 
Join Date: Jun 2020
Location: Fresno
Posts: 62
Default My $0.01

On my empennage I probably took it too far and primed all internal surfaces.

Like you, new to aluminum construction procedures. People I respect very much advised to not prime and maybe they are correct.

However, this is my future family member in the form of an RV10!

My procedure:

Prep as many parts as possible at once. Turn on the best garage music you can find. Debur and scotchbrite like a madman. I scrubbed every surface of everything.

Then, on a bright sunshiny day, set up multiple picnic tables on the driveway. Lay out all your parts and spray alumiprep on all of them. Have your paint process ready to go.

A quick scrub with scotchbrite and acid prep (alumiprep) and GLOVES. After about 15 minutes rinse thoroughly, let dry in the sun.

I used AKZO two-part epoxy. Mix it and give it the 30 minutes (?). Blow dry all your little parts just to make sure you've removed all water residue.

Move parts (with gloves to prevent oil from contaminating the surfaces) to your "paint booth".

I invested in a Hobby Air hood and air supply. Don your disposable cover-alls and gloves and have fun painting !!

AKZO: applies easily, dries fast, provides a super durable finish that looks good - if you like ugly green.

Bottom line: the process was not bad at all. Probably only four mornings spent on painting for the entire empennage.

Reach out any time to talk. Also, I am open to any and all advice.

Andy
__________________
RV10 Builder.
Aerobatics intro done and addiction started.
Thinking of being untrue to the 10 and finding an RV8.

Thanks to a COVID forced shutdown--re-evaluated and completing a 40 yr dream of flying and building.

PASSED THE CHECK RIDE !!
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  #4  
Old 05-25-2021, 03:23 PM
wirejock's Avatar
wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 4,544
Default Process

Quote:
Originally Posted by arr View Post
On my empennage I probably took it too far and primed all internal surfaces.

Like you, new to aluminum construction procedures. People I respect very much advised to not prime and maybe they are correct.

However, this is my future family member in the form of an RV10!

My procedure:

Prep as many parts as possible at once. Turn on the best garage music you can find. Debur and scotchbrite like a madman. I scrubbed every surface of everything.

Then, on a bright sunshiny day, set up multiple picnic tables on the driveway. Lay out all your parts and spray alumiprep on all of them. Have your paint process ready to go.

A quick scrub with scotchbrite and acid prep (alumiprep) and GLOVES. After about 15 minutes rinse thoroughly, let dry in the sun.

I used AKZO two-part epoxy. Mix it and give it the 30 minutes (?). Blow dry all your little parts just to make sure you've removed all water residue.

Move parts (with gloves to prevent oil from contaminating the surfaces) to your "paint booth".

I invested in a Hobby Air hood and air supply. Don your disposable cover-alls and gloves and have fun painting !!

AKZO: applies easily, dries fast, provides a super durable finish that looks good - if you like ugly green.

Bottom line: the process was not bad at all. Probably only four mornings spent on painting for the entire empennage.

Reach out any time to talk. Also, I am open to any and all advice.

Andy
That is an excellent process. Should serve you well. Love my Hobby Air.
Only thing I would add is when you move on to interior color, wipe surfaces with a tack cloth right before pulling the trigger. The tack cloth will grab any dust or particles.
__________________
Larry Larson
Estes Park, CO
wirejock at yahoo dot com
Donated 01/01/2021, plus a little extra.
RV-7A #73391, N511RV reserved (2,000+ hours)
Empennage, wings, fuse, finishing kit, now FWF
Disclaimer
I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #5  
Old 05-25-2021, 05:27 PM
Bandera Bandera is offline
 
Join Date: Feb 2021
Location: Gainesville, Tx
Posts: 34
Default

If you donít want to use an acid etch you can wash once with soap and water followed by washing two times with AKZO Metaflex SP 1050. Metaflex is a water based adhesion promoter. It works very well. AKZO 10P2111 primer goes good with that.
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  #6  
Old 05-27-2021, 06:58 AM
ravenstar ravenstar is offline
 
Join Date: May 2021
Location: New Hampshire
Posts: 15
Default

Quote:
Originally Posted by wirejock View Post
My opinion. Worth $.02

SEM is self etch so it's going to chemically etch the surface to promote adhesion. Lots of builders love the stuff. No personal experience.

There are some products you wouldn't use without a very thorough rinse. Bleach for instance. Some window cleaners have ammonia or vinegar. Test.

Test your paint. Shoot several tokens. One control with no cleaning. The rest cleaned or scuffed or both with various methods. Cure. Appy a section of black Gorilla tape. Leave it a day or two then rip it off. Go with whichever works best.
This I think is where I'm going for simplicity and minimal toxicity. My first experiment with the SEM was very positive. That stuff adheres better and is tougher than any paint I've used on any surface. But I don't have any experience comparing it to the other high end epoxy primers and paints. I've done epoxy/fiberglass work before and I'm a big fan of it in general. But I just don't see myself going through all the prep and cleanup work for all the parts that I will want to prime. This is a project I'll likely do in many frequent short work sessions. Self-etching seems the best fit for me, if it works.

To your point, I know the cleaner I used for my first test had ammonia in it, which I don't think I'd want to use on an aircraft part, though I haven't found anything definitive on that matter. I didn't try SEM without that cleaning, though, so I'll try the test you suggest along with a minimally prepped surface just to see what happens, thanks.

To everyone who replied, thanks. You've also got me reconsidering your approach. Perhaps I have the wrong impression of the effort involved in the preparation steps, so I'm going to go back and reread information the approaches you've suggested. I do want a high quality product, but it seems in the case of interior priming, it's very hard to sort out what different levels of quality mean.
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  #7  
Old 05-27-2021, 07:15 AM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Southwest
Posts: 1,590
Default Other camp

I am in the other camp.
I deburr all the parts, scrub with scotchbrite, wipe with acetone and shot the primer. No harsh chemicals to deal with except acetone and primer. Has worked well with very good adhesion. Same prep for painted parts. I am using shermin williams pg primer like the factory. Paint on key interior parts is jetflex, the good stuff. Never had a paint adhesion problem and very staisfied with ease of application and results.

My exterior paint will be a professional job with all the trimmings; i wont get near all those chemicals. Even with me applying the primer i use good protective mask and googles. Never breath the fumes of the primer chems, really bad for you. But the other steps are done in the open air. The mask goes on before the first can of primer chemicals is opened, and comes off when the last can is sealed and all the stuff is cleaned up and disposed of.

I did not use the alum prep, or any other surface treatment prior to prime, only acetone wipe.
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John S

WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for their use.

Dues paid 2021, worth every penny

RV9A- Status:
90% done, 90% left to go
Firewall Forward 5% in work
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www.pilotjohnsrv9.blogspot.com

Last edited by PilotjohnS : 05-27-2021 at 07:18 AM.
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  #8  
Old 05-27-2021, 02:00 PM
David Z David Z is offline
 
Join Date: Aug 2010
Location: Thunder Bay Ontario
Posts: 698
Default

I use Alimiprep for everything. Apply it with scotchbrite pads, rinse off and look for the clean water sheeting.

Next, I bought a gallon of Prekote. We'll see how that goes. Going to do some more research, but it sounds like Prekote does NOT chemically etch the metal, so might be doing some form of acid etch before Prekote. Likely be weak mix of Alumiprep, water rinse, then Prekote, air dry, spray primer.
__________________
RV8
Empennage Passed Pre-close Inspection
Wings mostly done
Fuselage at the "porcupine stage"
83126
Dash 8 day job is financing the RV8
Donation till September 2021
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  #9  
Old 06-13-2021, 04:15 PM
StressedOut StressedOut is offline
 
Join Date: Jun 2017
Location: Fullerton, CA
Posts: 157
Default

Soap and water wash with Dawn, then rinse. Spray with Prekote and scuff the surface with maroon Scotchbright, then final rinse and dry with clean wipes.

The Prekote directions say to do it twice. The second time scuff it 90 degrees to the first direction so you get a cross hatch scuff. I admit that sometimes I only do a single pass and it doesn't seem to affect the results.

I don't use Alumiprep or Alodine (Bonderite) because the runoff is considered toxic waste and needs to be captured and disposed of properly.

I use Akzo two-part epoxy green primer and the stuff is tough as nails if you do the surface prep correctly. I'm considering switching to Ekoprime though.
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RV-14A Kit#140433
Completed: Vertical Stab/Horizontal Stab
Scrapped: Rudder
Working on: Empennage (Elevator, Rudder #2, Aft Fuselage)
Ordered: Wing Kit (Arrives March 2021)
Construction log - mykitlog.com/ajackson
Dues paid on March 2021
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  #10  
Old 06-14-2021, 05:40 AM
David Z David Z is offline
 
Join Date: Aug 2010
Location: Thunder Bay Ontario
Posts: 698
Default

Quote:
Originally Posted by StressedOut View Post
The Prekote directions say to do it twice. The second time scuff it 90 degrees to the first direction so you get a cross hatch scuff. I admit that sometimes I only do a single pass and it doesn't seem to affect the results.
What happens if you scuff in circles?
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Empennage Passed Pre-close Inspection
Wings mostly done
Fuselage at the "porcupine stage"
83126
Dash 8 day job is financing the RV8
Donation till September 2021
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