The priming process (How Do You Choose?)

papakeith · Post by **papakeith** » Tue May 22, 2007 10:58 am

I've been through this a few times with CJ, but still find myself waffling between the different choices and protocols. I could use some help here.

Some that I speak with say, "Wash, Etch, alodine, primer". Some say,"wash, scuff, self etch prime. Still others say, "Mah Cessner ain't gots no primer an' is 50 yeahs owld an' luks jess fine."

I've dismissed the "do nothing" option. I'm just not willing to do that.

I'm still torn, however, on just what is considered acceptable. I don't want to skimp now and be stuck when I'm 70 with an large corrosion problem.

That being said, what are the major differences between the full blown etch, alodine, prime method, and the self etching primer besides the lack of a few messy steps? Is one vastly superior to another? Do the self etching primers need a top coat? If they do that brings me up to almost the same amount of trouble to do either method.

I'm here to learn, so . . . learn me something.

N537TM · Post by **N537TM** » Tue May 22, 2007 11:57 am

Pap

I don't want start a big Primer Wars again...

My thought's on the subject...and the way I'm do'in my prime / paint

Clean surface with MEK
Clean Surface with DeNatured Alcohol
Green Scotch Bright
NO ETCH... gets in ..under rivets , overlap joints
Clean with MEK
Clean with DeNatured Alcohol
Water break test... no bead up's allowed
Mil Spec Chromate Epoxy Primer ( sherw Will) PRF-23377H light coat

Total time between Scotch bright and Primer is no more than 6 hours

NASON Hi Fill Primer (polyester)
sand
Clean with DeNatured alcohol
NASON hi fill prime
sand
Clean with Denatured
Base coat color Dupont
Clear coat Sher Will

Mike

papakeith · Post by **papakeith** » Tue May 22, 2007 12:10 pm

actually, I'd prefer that we did start a primer discussion(war). I want all of the ideas on how to proceed, and reasons for doing so. The more I can read about other's decisions and procedures, the better informed my final decision should be.

Brantel · Post by **Brantel** » Tue May 22, 2007 1:30 pm

I have switched to the Stewart Systems/AFS Waterborne primer.

This stuff can be cleaned up with water and is safe to use.

I clean any stickers or anything like that with MEK, acetone, or L. Thinner.

I use the Stewart/AFS acid etch while maroon scotchbriting the parts.

Rinse and let dry and then spray the primer with a seudo HVLP Harbor Freight gravity feed gun. I then pour the leftovers back into the jug and wash the gun with water.

This stuff is easy to work with and provides better scratch resistance than the rattle can self etching stuff. They also advertize it as providing excellent corrosion protection.

It does take a little while to dry expecially when you have a high humidity.

papakeith · Post by **papakeith** » Tue May 22, 2007 1:39 pm

I've been looking at the Stewart system. They seem to be lacking on online documentation though.

Brantel · Post by **Brantel** » Tue May 22, 2007 1:58 pm

papakeith wrote:I've been looking at the Stewart system. They seem to be lacking on online documentation though.

Call them, they have been helpfull. I know that they bought the company from AFS a while back. They have some info that is mixed in with the procedures for the fabric stuff.

It seems to be good stuff! Not as tough as two stage but better than rattle can/self etch. I was using Marhyde but this stuff is superior to that as far as toughness.

The Marhyde won't take a dimple without cracking off the base metal. this stuff does.

When you first spray it, it looks like it has a bad case of orange peel but as it dries this goes away to a beautiful smooth finish.

All the pics I have posted here are of parts primed with it.

cjensen · Post by **cjensen** » Tue May 22, 2007 2:36 pm

I think it really depends on your geographical locale and climate. You guys on the coasts NEED protection. Those of us in the middle, not so much. I started out with NAPA 7220 self etch, and that's what I still use. I does need a topcoat to seal, but I'm not topcoating much of anything. It provides some protection by itself, but around here, midwest airplanes are well known for their longevity and resistance to corrosion.

I've since really lightened up on application of primer. I'm not priming anything in the cabin, but I am painting it. I primed and sealed the longerons, just primed the aft bulkheads, and skins are bare.

My method is this...alcohol wash, maroon pad, MEK, self etch primer, done.

tshort · Post by **tshort** » Tue May 22, 2007 3:55 pm

I have done etch / alodine / AKZO 2 part epoxy for all of the interior parts (except skins - although I did the skins on the tail, as they are not accessible). My thought is that I KNOW it will be good forever - I have no plans to sell the airplane. All the other stuff I've tried (rattle cans, etc) either scratches off too easily or wipes off with acetone / MEK / etc.

I guess one other argument for that in your case is that you are spending all the time and effort making the parts - why not protect them as best you can?

T.

papakeith · Post by **papakeith** » Tue May 22, 2007 4:17 pm

One of the issues I have is with the "It's alclad" statements I see so often. maybe the bulk of the part is alclad, but every cut edge is exposed alloy. That is what bothers me most, I think, about self etch primer with no topcoat. If I were to alodine treat it, those edges would go through a conversion and get a layer of protection.

Sometimes I think about just alodining and forgetting about the primer altogether.

captain_john · Post by **captain_john** » Tue May 22, 2007 4:58 pm

Sometimes I think about putting a sharp pencil into my left eye. I don't ever do it, though!

CJ

Post by **Spike** » Tue May 22, 2007 5:13 pm

papakeith wrote: Sometimes I think about just alodining and forgetting about the primer altogether.

Perfectly acceptable to me. Ive been alodining parts whenever I can, and only spraying them where parts are fastened in case water gets trapped.

Guess Ill need that pencil John.

aparchment · Post by **aparchment** » Tue May 22, 2007 8:08 pm

captain_john wrote:Sometimes I think about putting a sharp pencil into my left eye. I don't ever do it, though!

Yessah, that's a good thing cuz I'm almost out of #2s and wuz gonna borrow yours.

On a serious note, I had been doing the alumiprep, alodine, Akzo route until recently. Then I started washing, scuffing, wiping with CleanEZ, spraying 7220 and then Akzo. Now I am going to switch to washing, scuffing, cleaning and spraying Nason. The first process just was too labor intensive for me particularly since you really can't do it all indoors. That isn't so great when you are building in New England.

Womack2005 · Post by **Womack2005** » Wed May 23, 2007 6:51 am

From day one my process has been the same:

Wash part in soapy water with maroon scotch brite.
Rinse and hang to dry.
Wipe down with acetone while still hanging.
Shoot with VeriPrime.

Done.

papakeith · Post by **papakeith** » Wed May 23, 2007 8:56 am

Sometimes I think about just alodining and forgetting about the primer altogether.

captain_john wrote:Sometimes I think about putting a sharp pencil into my left eye. I don't ever do it, though!

CJ

why do you say that john?

LooseNut · Post by **LooseNut** » Wed May 23, 2007 11:18 am

Here's my recipe for individual parts before any assembly:

Peel: remove all blue film
Wash: soap (Dawn), use kithchen scotch-brite/sponge thingy.
Rinse: water.
Dry: drip dry, wipe down with paper towel, compressed air, whatever.
Clean: acetone, paper towels.
Etch: acid wash stuff, maroon scotch-brite.
Rinse: lots of water.
Dry: as before.
Alodine: small parts that fit in the bucket, don't do big parts
Prime: VeriPrime, spray with small "detail paint gun", keep it light

For assemblies and touch ups,

Clean: acetone, paper towel or maroon scotch-brite
Prime: VeriPrime, tiny brush or spray

I avoid using the acid etch on any parts that I think I might not be able to rinse properly -- no rivets, no mating parts. For that reason, I always remove all the blue film from the aluminum before I prime.

papakeith · Post by **papakeith** » Wed May 23, 2007 6:36 pm

I just got off the phone with Dan? and Margie at Stewarts Systems (the company that bought AFS). I have decided to give their product/system a go.

Is it the right decision? I don't know. But at least it's a decision. I've wasted too much time hemming and hawing. I needed to get the ball rolling on this.

MachineMan · Post by **MachineMan** » Wed May 23, 2007 8:32 pm

Sounds like you've already decided on a direction...
but I throw one more out there.

I've been priming with a Sherman Williams (water based) DTM Wash Primer
http://www2.sherwin-williams.com/Apps/P ... data&id=35

For prep,
Scrub with ZEP "purple" cleaner/degreaser with maroon scotchbrite, (With this I achieve the "scuffing" and deep cleaning for primer prep on one step.)
I wash very well with hot water,
Parts come out very clean (no water beading)
Then dry w/compressed air.
Prime, Done

-So far I have primed my Emp and I like everything about it
-The cost is about 55.00/gal,
-Cleans up with water.
-Seems durable in handling and assembly/riveting.
-Accept's "hot" top coats, (solvent based, acrylics, epoxys etc)
-Matches the SW Wash primer that Van's uses on the Quick Builds

cnpeters · Post by **cnpeters** » Wed May 23, 2007 10:31 pm

Fun topic. I basically do the quick and easy way as Chadenfellner ':P' with the Napa 7220. As a practioner of "evidenced based medicine", I like to see real evidence that something like this is worthwhile, and I was hard pressed to uncover much after a month of research. Tons of anecdotes, little proof. There was even a set of test panels left outdoors in coastal Oregon (Alclad, primed with various products) that didn't show much difference after a year or two (details now murky). So, even if you dismiss the 'do nothing' approach, if there isn't much evidence out there for additional corrosion protection, it really wouldn't matter what method you choose if you insist on doing something. So pick was is easiest, cheapest, and the least toxic. Maybe there is contrary evidence, but I couldn't find it. Good luck on this difficult topic.

Thermos · Post by **Thermos** » Thu May 24, 2007 6:40 am

PK -

Alodine does a good job providing corrosion resistance. However, the corrosion-proof layer that it leaves is thin and easily removed by scuffs, scratches, etc. If that won't happen to the parts you're thinking of alodining, doing that and nothing else might be a good choice especially if you want to build a light airplane.

Alodine is hazardous, toxic stuff so I finally stopped using it. The application sheet for the primer I use (Super Koropon) says that if you can't use alodine, don't - it's not required - and I figured that alodine and a chromated epoxy, fluid-resistant primer was overkill anyway.

Dave

cjensen · Post by **cjensen** » Thu May 24, 2007 9:51 am

I have a 'test cell' in my backyard going right now. The two training kits that I put together in the summer of '05, have been out back in the weather since Feb '06. After a full year outside just sitting there (I have not move it), the bare Alclad is still shiney new, and the 7220'd area is still protecting the Alclad. The area of interest, is where I have a brick laying on top of them to keep the wind from taking my experiement away from me. Under the brick, the Alclad is still holding up, but it is SEVERELY discolored. Now, a brick holds a TON of moisture if not sealed, so this is the main factor in that area. BUT, we don't put bricks on our airplane's, so the area's around the brick are the conclusive (up to today) points so far.

I'll post a pic later today if anyone is interested.