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Almost done with my own little prime war...

RV7ForMe

Well Known Member
Hey.... So for the better part of 6 weeks I have been pretty busy fighting my own little prime war!

So this is just what the result of all that time and money is.

1: I tried Auto Dupi Color Rattpe can (grey) non etching - easy to use, cheap, scratches easy, dont like the color

2: I tried waterborne Aviation primer (non toxic) with HVLP gun - Looked good, expensive, did not stick well at all. Came of with duck tape and scratched easier than rattle can. Was a real pain to get to spray right. either to runny or to coarse. PITA INMO

4: TRIED REALLY HARD TO GET AKZO....Cant get it here, would have to import, would cost over 400$

5: finally decided on a Aviation high solids 2 part epoxy that looks similar to akzo but less toxic I think. does contain Cromates. also expensive but not as bad as Akzo...

Results: Used it on scrap metal for testing only. Spays really nice and easy. any runs and orange peeling I thought I had on parts disappeared after drying. I Like that.

Now How durable is it? how durable is other stuff? Anyone want to look at this video and see what I got? This was after 24h after spraying. I had expected it to be tougher... but maybe this is just how all primers are. Maybe it will be better after a week of drying...

Video scratch test

download


---No need to get popcorn. I have decided I want to prime and now I will use this stuff because I am not buying a 3rd type of primer. Just wanted to see what other stuff is like. because I keep reading "tough as nails" on all 3 products I have used....
 
Prep

Couple of questions.
1. What was used to test adherence and scrating?
My test is a piece of Gorilla tape. Rub it on, leave it overnight then rip it off.
Scratch test is my wife's fingernails.
2. What's the prep process. Aluminum oxide forms pretty quick and is the enemy of adhesion. My preference is maroon scotch brite, dimple, wash with Bon Ami and grey scotchbrite, rinse, dry, spray.
I use P60G2 primer but that's another war.
 
The epoxies might need more than 24 hours to reach full strength, especially if the temps are under 70F or so.

Re-try the epoxy scratch/tape test after a week of curing.
 
Just to clarify

My process was just 2 pieces of test so I did 3 different prep works hence the 3 different areas on the picture to see what works best.

1. just aceton wipe

2. Aceton and manual scotch brite rub

3. the thinner supplied with the paint and manual scotch brite rub

this was done less than an hour before paint.

Result: honestly I cant even tell the difference.

I used my nails (leaves marks but doesn't go to metal)
and my Keys as shown in the video. (it will eventually go to metal)

Paint temp wasnt ideal so yes I will give this a couple more days and see.
 
They used some version of Koropon on the Space Shuttle Orbiter. I didn't know it was available for us "civilians". Thanks for the tip.

If it's this one, it looks very similar to the AKZO favorite, but with the advantage of coming in a qt. kit.

http://www.skygeek.com/prc-desoto-5...aign=froogle&gclid=CI3P-5L07tACFYpgfgodNmwA7A

I note it's to a Boeing spec, whereas the Akzo is to a McDonnell-Douglas spec., with both specs for a similar "fluid resistant interior primer" function.
 
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Give SEM self etching primer a shot if you can get it shipped reasonably. It's a rattle can that goes a long way and is really durable. It's about $20 USD per can, but a lot easier than having to mix and spray then clean equipment. I've found good deals on Amazon.
 
Give SEM self etching primer a shot if you can get it shipped reasonably. It's a rattle can that goes a long way and is really durable. It's about $20 USD per can, but a lot easier than having to mix and spray then clean equipment. I've found good deals on Amazon.

I do not live in the US. So that is/was my main problem. The PPG stuff vans uses. Not sold here... Akzo not sold here... SEM self etch not sold here...Shall I continue?

I ended up asking Akzo nobels official distributor in the Netherlands... Wont sell to "normal" people... I have been wasting a ridiculous time and effort on this topic.

The stuff I have now is MIL-C-85285B, MIL-P-23377, MIL-PRF-85285. So I guess It cant be that bad.

I haven't set a single rivet because of this and I have the HS, VS and rudder ready to GO!
 
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DuPont Variprime 615S

I am on my second project and I have become a fan of using a sponge brush to apply variprime 615S metal etch primer that is mixed very thin. I find it quick and easy, inexpensive and effective. If I have just a few parts that need primer, I don't have take time to set up for spray, or mix a large amount. I can mix a thimbleful and sponge brush it on. It dries very quickly, and when mixed thin, does not leave brush marks.

After deburring and using scotch bright pad, I clean the parts with a degreaser type detergent in a spray bottle, then dry with clean rag as I mix up the variprime. You don't have to keep the parts super clean because the metal etch properties will cut through small amounts of contamination like finger prints.

rj33hy.jpg


I can be back to riveting together primed parts in 30 minutes or less. It seems to save me a ton of time, and minimize wasted material which makes it inexpensive. The 615S that I buy at the local auto paint store says it has chromate in it, so I think it has sacrificial anode properties to reduce dissimilar metal corrosion.

I don't scotch bright external skins prior to sponge brushing primer, in case anyone wants to go to a polished aluminum surface later. I also sponge brush prime skins before I do any dimple countersinking. If you dimple before priming, the dimples will squeeze out extra primer from the sponge and can cause a drip on the opposite side.
 
Give SEM self etching primer a shot if you can get it shipped reasonably. It's a rattle can that goes a long way and is really durable. It's about $20 USD per can, but a lot easier than having to mix and spray then clean equipment. I've found good deals on Amazon.

I've also been using SEM - it's pretty good stuff. I found it a couple bucks less than Amazon at Summit Racing (summitracing.com)
 
Thanks for your input...

Thanks for all the suggestions and what you guys are using. As I said before most of the stuff you use I cant get. So I would like to know how tough your primer is and how tough it has to be? That's why I posted the video to show you what I have got....

Video scratch test
 
I started my build by priming everything with a rattle can self etching primer. It slowed the build process down a lot. I also fly a 49 year old Cessna with no primer and the metal still shines with very little corrosion anywhere. Then again I do not live near salt water and am in a semi-arid climate. Long story short, I elected to do the remainder of my build using no primer and counting on the ALclad for protection. I only prime non-Alclad parts. At my age, I'll be extremely fortunate to get 20-30 more years of flying. Besides, I just looked over a B-25 and two Corsairs this past weekend from the early 1940's. Worn but still flying!

Just saying that no primer may be an option for you to consider especially if primer is hard to get.
 
I started my build by priming everything with a rattle can self etching primer. It slowed the build process down a lot. I also fly a 49 year old Cessna with no primer and the metal still shines with very little corrosion anywhere. Then again I do not live near salt water and am in a semi-arid climate. Long story short, I elected to do the remainder of my build using no primer and counting on the ALclad for protection. I only prime non-Alclad parts. At my age, I'll be extremely fortunate to get 20-30 more years of flying. Besides, I just looked over a B-25 and two Corsairs this past weekend from the early 1940's. Worn but still flying!

Just saying that no primer may be an option for you to consider especially if primer is hard to get.

Very true! I have given it some thought. My reasoning was that the 172 I flew was primed and its a good thing. The runway dead ends in the salty north sea...Around here everything will rust. Just a matter of time. Also I do like the green color. makes it look like a war bird :) Also Since I am new at this I do scratch things up and after priming the parts looks so pretty. I have played with a few primers and I will now use the last one I bought. It seems to get harder with a week or so. I still have to do some chemical testing with AVGAS but otherwise I think I have a winner that is "good enough" for me.
 
Tetrosyl Etch Prime.....

Available in UK and Europe from Fleabay or Amazon.

50/50 mix with a splash of celly to thin.

Sticks like sh it to a blanket.

?70 for a 10 litre mix.

It even comes with a CDO certificate :rolleyes:

Simple, good, green, won't scratch off, better than Cessna's best.
 
Interesting idea. How thin do you mix it?

I mix it about 2 parts accelerator to 1 part primer. And will thin a bit more if it thickens in the pot during application, or if I need to stretch it a bit to complete whatever I am priming. For me it seems like the important thing is that it be thin enough to flow out well after the sponge brush stroke, so you don't get any brush marks. Yes, it is a 2 part epoxy, but I have found that over thinning doesn't seem to interfere with curing or durability.

mc8c4o.jpg
 
Primer

Sam........do you plan on top coating the Variprime? I have been using Nason self etching primer, a cheaper Dupont primer. It doesn't go on as good but has a similar appearance. I had planned on shooting a finish coat but I like the look of the primer. Just curious what your plans were.
 
Boomer

You guys be careful to rinse your parts good of any cleaner that's soap as its a release agent.
Bob
 
I agree with all Sam said except that Variprime is not a two part epoxy. It is a two part self etching primer which adheres extremely well. I clean with thinner before use and a maroon Scotch Brite pad.
 
SEM

Give SEM self etching primer a shot if you can get it shipped reasonably. It's a rattle can that goes a long way and is really durable. It's about $20 USD per can, but a lot easier than having to mix and spray then clean equipment. I've found good deals on Amazon.

SEM is a really great product and worth the money. Dries very fast and is
extremely durable. Great for aluminum, not so on steel. Epoxy primer for steel
And high wear areas.
 
I mix it about 2 parts accelerator to 1 part primer. And will thin a bit more if it thickens in the pot during application, or if I need to stretch it a bit to complete whatever I am priming. For me it seems like the important thing is that it be thin enough to flow out well after the sponge brush stroke, so you don't get any brush marks. Yes, it is a 2 part epoxy, but I have found that over thinning doesn't seem to interfere with curing or durability.

...

Careful using more accelerator (DuPont actually calls it a converter) since that is the part that contains the actual acid ingredient - phosphoric acid.

It thickens quickly since a lot of the rest of the converter component is a blend of solvents, and that is probably what overcomes small fingerprint spots you mention in your first post.

It is not an epoxy so extra converter is simply adding more acid and rapidly evaporating solvents to the mix.
 
For some parts I have also been sponge brushing primer. I am using the Sherwin Williams Sherwin-Williams CM-0724400 chromate primer. I mixed it at normal spraying strength for the first brush coatings but I will probably try reducing it next time to minimize some issues I had with inconsistent thickness.
 
Take a quick google on filiform corrosion aluminum. Also take a look at Ch6 of AC43-13 which you can download for free. Its a good treatise corrosion and corrosion mitigation wrt aircraft (just one of the fed works on corrosion) Not the be all and end all, but a good starting point. Doesnt cover some of the ACF, Corrosion X post build type of remediations/mitigations in use these days however.

BTW noone learns about corrosion until they come across it, so dont think youre behind the curve or anything. I didnt know anything until I found some corrosion pits on my wing spars. Then someone else showed me the references and such. Yea for VAF! :)
 
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Sam........do you plan on top coating the Variprime? I have been using Nason self etching primer, a cheaper Dupont primer. It doesn't go on as good but has a similar appearance. I had planned on shooting a finish coat but I like the look of the primer. Just curious what your plans were.

I do not plan to top coat the variprime inside the airplane, except for the panel, throttle quadrant and C/B and switch panel as shown in the picture. The top coat on those items is DuPont single stage Imron (now called Axalta AF400). The exterior will have a top coat, but I am still not sure how I am going to approach that. The variprime will need to be re-activated somehow. I might just clean/degrease and spray on a second light coat of variprime before the top coat.
 
Careful using more accelerator (DuPont actually calls it a converter) since that is the part that contains the actual acid ingredient - phosphoric acid.

It thickens quickly since a lot of the rest of the converter component is a blend of solvents, and that is probably what overcomes small fingerprint spots you mention in your first post.

It is not an epoxy so extra converter is simply adding more acid and rapidly evaporating solvents to the mix.

Thanks for the clarification that variprime is not actually an epoxy. I always wondered about that a bit. But it does make more sense that it is not an epoxy.
 
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