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PreKote + Akzo - what am I doing wrong?

rdamazio

Well Known Member
Hi all.

I chose to use PreKote + Akzo for my plane, and today I did my first primer test on some scrap pieces, which I don't think went very well. I used a HVLP gun set at 20psi, but the end result looks like this:

IMG_20150301_165411.jpg


IMG_20150301_165418.jpg


I tried a few different adjustments on the gun (pattern, air flow, etc.) but it didn't seem to improve - is this the way it's supposed to look? Assuming not, any hints on what I may be doing wrong?

(total primer/painting newbie here btw)

Thanks!
 
Interesting - is that 20psi at the gun? I'm guessing your pressure is too low. A pic for comparison:

DSC_3699.jpg
 
Spraying primer

20 psi is about right if it's at the gun. You should have a flow valve with a gauge right at the gun. Maybe a water/oil filter and flow valve if your in a humid environment. The manufacturer recommended psi is a good start. 23 on mine. Also it will recommend a starting point for the needle valve position. 3/4 turn open on mine. You should see the fan of paint when you pull the trigger to the paint position. The trigger has two positions. When you first squeeze, it feeds air. As you pull farther the paint flows. This allows you to keep the air flowing and control the paint. Most guns have the fan control almost wide open.
It looks like very little or nothing came out.
Try spraying something cheap like lacquer thinner or even water to see how the trigger works and what the fan looks like when the liquid flows.
 
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I would say, after watching your time lapse video, that you didn't stir the Akzo enough. Part A ( the green stuff) needs to be stirred really well especially if it has been sitting for a while. All the solids will settle to the bottom and there can be a couple inches of solids on the bottom that are really hard to stir up. I always use a mixing stick to stir so I can feel whats on the bottom of the can.
 
Time Lapse

I would say, after watching your time lapse video, that you didn't stir the Akzo enough. Part A ( the green stuff) needs to be stirred really well especially if it has been sitting for a while. All the solids will settle to the bottom and there can be a couple inches of solids on the bottom that are really hard to stir up. I always use a mixing stick to stir so I can feel whats on the bottom of the can.

I missed that. Yep. Looks like a mixing problem.
I would suggest a big tarp to protect the area. Nice patio.
Also, buy some cheap vet syringes to measure. Clean and no waste for tiny jobs.
 
I missed that. Yep. Looks like a mixing problem.

+2 if that was a new can and you only used the Mixing Mate, that's your problem - at least part of it. I use a normal paint stir stick, and for a new can it takes quite a while to mix everything that settles on the bottom.
 
I missed that. Yep. Looks like a mixing problem.
I would suggest a big tarp to protect the area. Nice patio.
Also, buy some cheap vet syringes to measure. Clean and no waste for tiny jobs.

Yep, I fully agree, not mixed. Those mixers will work, but a paint shop might spin it for a while. The color did not show on the cardboard, so definitely not mixed.

Those mixers also have very precise valves and 1/2 oz can be easily dispensed, but to be accurate, use scales - that is what a paint shop does these days. I hate cleaning those syringes all the time.

I would not remove the respirators until the gun is cleaned.
 
Bit hard to tell from the photos, but it looks like the sheet of blue protective covering is still on the parts. That will need to be removed first. Should peel off fairly easily, unless the parts are quite old, then it takes some more effort.

Ah, I think the blue tint is just an effect of the lighting - I definitely did remove it :) scrubbing the scotchbrite with prekote would probably have made a mess otherwise.

Interesting - is that 20psi at the gun? I'm guessing your pressure is too low. A pic for comparison:

Yours looks awesome :) Yes, it's 20psi at the gun, while not spraying - I did notice that the pressure indication goes down significantly when I actually actuate the gun (when air is flowing), I was also assuming that would be normal (static vs dynamic pressure and all that) - should I be adjusting for 20 while spraying instead?

I would say, after watching your time lapse video, that you didn't stir the Akzo enough. Part A ( the green stuff) needs to be stirred really well especially if it has been sitting for a while. All the solids will settle to the bottom and there can be a couple inches of solids on the bottom that are really hard to stir up. I always use a mixing stick to stir so I can feel whats on the bottom of the can.

I missed that. Yep. Looks like a mixing problem.
I would suggest a big tarp to protect the area. Nice patio.
Also, buy some cheap vet syringes to measure. Clean and no waste for tiny jobs.

+2 if that was a new can and you only used the Mixing Mate, that's your problem - at least part of it. I use a normal paint stir stick, and for a new can it takes quite a while to mix everything that settles on the bottom.

Yep, I fully agree, not mixed. Those mixers will work, but a paint shop might spin it for a while. The color did not show on the cardboard, so definitely not mixed.

Those mixers also have very precise valves and 1/2 oz can be easily dispensed, but to be accurate, use scales - that is what a paint shop does these days. I hate cleaning those syringes all the time.

I would not remove the respirators until the gun is cleaned.

Aha, thanks!! The contents of the can looked kind of homogeneous, that's why I didn't think stirring that much was needed.
Yes, it was a new can, just removed the hazmat seal a few minutes before - I'll definitely try again and stir it much more this time - I'll report back with new pictures.
 
Ah, I think the blue tint is just an effect of the lighting - I definitely did remove it :) scrubbing the scotchbrite with prekote would probably have made a mess otherwise.
Now that I look at it on a full size monitor I see it better. Ironically, I thought the dress was white... No offense meant by the suggestion; you wouldn't be the first new builder to prime over the plastic.
 
Get a good paint mixer

Stop by the aviation isle at Home Depot and pick up one of these paint mixers:

http://www.homedepot.com/p/Workforce-1-Gallon-Helix-Paint-Mixer-HM1HD/202251542

It chucks into your cordless drill and does a great job with the solid that settle at the bottom of the can. I actually run it at the lowest speed (hight torque setting) on my drill, and I run it CCW to minimize the amount of churn in the can, especially when full. Works great to get a uniform mix without shaking.
 
Stop by the aviation isle at Home Depot and pick up one of these paint mixers:

http://www.homedepot.com/p/Workforce-1-Gallon-Helix-Paint-Mixer-HM1HD/202251542

It chucks into your cordless drill and does a great job with the solid that settle at the bottom of the can. I actually run it at the lowest speed (hight torque setting) on my drill, and I run it CCW to minimize the amount of churn in the can, especially when full. Works great to get a uniform mix without shaking.

Actually, the on-can mixers he has are quite good if turned for an adequate length of time. The bottom of the mixer contacts the bottom of the can. He just needed to turn it for about 10-15 min for the first time.
 
You might consider getting the cheap paint can shaker at Harbor Freight. It makes quick and thorough work of the epoxy paint mixing. Don't let your friends know cuz you will be the neighborhood paint shaker its so awesome! If you do get it forget the little oiler it is terrible. And it makes a lot of condensation to putting it with a drain line is a good idea.
 
Prekote

I have no exp with azco, I do want to comment on prekote. I used it on my entire rv8. It is a lot of work. The directions specifically say to apply and scrub with scotbrite, rinse well the reapply and scrub again 90 degrees from the first(don't scrub so hard to remove the Alclad finish). Please note that when rinsing the final product you should see the water actually sheet off of the surface. If there is an area that did not get done enough, the water will tend to bead up there, redo that area. Also to prevent contamination I dried only with dry filtered compressed air, no rags of any type and no touchy with bare hands after this process.

When spraying I found my epoxy primer to flow out nicely and the whole paint job came out rather nice. I used epoxy primer and kirker base coat/ clear coat process.

Bird
 
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I have no exp with azco, I do want to comment on prekote. I used it on my entire rv8. It is a lot of work. The directions specifically say to apply and scrub with scotbrite, rinse well the reapply and scrub again 90 degrees from the first(don't scrub so hard to remove the Alclad finish). Please note that when rinsing the final product you should see the water actually sheet off of the surface. If there is an area that did not get done enough, the water will tend to bead up there, redo that area. Also to prevent contamination I dried only with dry filtered compressed air, no rags of any type and no touchy with bare hands after this process.

Thanks, sounds like I'm doing this part correctly then :)

(still haven't had a chance to retry the primer - will most likely do it next weekend)
 
Success! :) Thanks for the advice.

Here's a picture of the result (with the previous result next to it for comparison):

IMG_20150321_221639.jpg
 
I'm late to this party, sorry about that, but a few comments for your perusal RD.

Based on your last pic, it looks to me that you have it on too thick now. Ok what's wrong with too thick? Nothing really, except a bit o' weight. That said, after I clean my part (prekote etal) I use a black sharpie to either mark the part number or whatever and then shoot the Akzo on the part. If I cover paint the part and can't see any shiny AL, but can still read the sharpie writing, its the right thickness. Its less coverage than you would think - might be two passes, but usually just one (YMMV wrt fan pattern).

Also, I'm a firm believer in using a primer pistol for Akzo, not a gun. The gun is overkill - way over kill - and clean up with a gun is just a PITA. The pistol is a simple siphon grade school "system" but works excellent for akzo. I do little parts and full sized skins with it - all the same.

http://www.aircraftspruce.eu/primer-pistol.htm

(Not sure why its showing up on the the EU site and not the US site, but you got a pic here.)

I got mine from the US site (in Sept14), and I use 10psi to shoot it. Clean up is a quick shoot with some acetone and wipe out the cup and reuse. Nothing is easier, not even using a brush.

Oh yeah and on mixing, all I do is shake my paint single part up side down using my arms - maybe 20 or 30 seconds (good upper body work out!), and open and mix with the second part. I guess you could use a paint shaker, but I've not found it even remotely necessary, and I don't own one. You could also store the paint single part upside down so the solids float to the top (errr, bottom?), and shake it again before use. Naturally make sure your lid is on well, and maybe store it in a bucket incase it leaks. But again, I don't do this either way, and found no need for it.

Just my .02
 
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shaking paint

I normally do my priming in large batches which means months and month pass beteeen painting. Very lazy and want a good mix so i duck down to the local Bunnings (like wallmart) and get the paint guys to chuck the Akzo base can on the shaker for a few minutes while.i wander around and buy more tape, thinners, gloves etc.
 
<snip> If I cover paint the part and can't see any shiny AL, but can still read the sharpie writing, its the right thickness. Its less coverage than you would think - might be two passes, but usually just one (YMMV wrt fan pattern).

Mani,
(from another thread) http://www.vansairforce.com/community/showthread.php?t=115757&page=2:

"Out of curiosity, I brought a primed part into work and measured the dry film thickness with a PosiTector 6000 N1 meter.
The recommended dry film thickness is 1.0-1.3 mils per the Akzo tech sheet.
My part measured between 0.25 and 0.8 mils.
Observations:
If you can see the shine of the metal through the primer, it is about 0.25 mils.
If you can sort of see through the primer, like barely make out streaks in the chromate or probably mill markings (if you didn't clean them off), it is about 0.5 mils.
If the coating is opaque, it is probably at least 0.7 mils.
I don't know how much Sharpie markings will bleed though as I don't leave them on."
 
Also, I'm a firm believer in using a primer pistol for Akzo, not a gun. The gun is overkill - way over kill - and clean up with a gun is just a PITA. The pistol is a simple siphon grade school "system" but works excellent for akzo. I do little parts and full sized skins with it - all the same.

http://www.aircraftspruce.eu/primer-pistol.htm

(Not sure why its showing up on the the EU site and not the US site, but you got a pic here.)

I could not find this on Spruce, but ATS has it...

http://www.aircraft-tool.com/shop/detail.aspx?PRODUCT_ID=SA-PP01
 
Spray gun

I use both. HVLP for big jobs. Primer Pistol for small jobs. Usually that's the amount the film container holds. I prefer high pressure on the primer pistol though. 50 psi. It atomizes better to my preference. I also ditched the little tubes and made a brass tube for the feed so it picks up all the way down to the bottom. I have a water/oil filter and flow valve on mine. I too use one container and wipe it out after shooting some lacquer thinner. Add a temporary down draft paint box and outside temp no longer matters.
 
Mani,
(from another thread) http://www.vansairforce.com/community/showthread.php?t=115757&page=2:

"Out of curiosity, I brought a primed part into work and measured the dry film thickness with a PosiTector 6000 N1 meter.
The recommended dry film thickness is 1.0-1.3 mils per the Akzo tech sheet.
My part measured between 0.25 and 0.8 mils.
Observations:
If you can see the shine of the metal through the primer, it is about 0.25 mils.
If you can sort of see through the primer, like barely make out streaks in the chromate or probably mill markings (if you didn't clean them off), it is about 0.5 mils.
If the coating is opaque, it is probably at least 0.7 mils.
I don't know how much Sharpie markings will bleed though as I don't leave them on."

Yes I read that also before I chose to use Akzo. In the end though, I find just using my Mark1 eyeball isn't good enough. The sharpie and one or rarely two passes with the primer pistol satisfies me as GTG. I don't have an industrial calibrated gun technique so I'm sure its not uniform over the entire part anyway, but its covered and I move on. Also realize that I'm not chromating as described in the quote, so I don't have the added layer of sacrificial protection to rely on.....
 
Primer pistol tweaks

I got asked via PM how to make the primer pistol work properly, as its a **** shoot as to whether you get a good one out of the box or not. I've coped my reply below, but suffice it to say that you can tweak your gun very easily to make it work proper, no matter how it works when you first fire it up. I recommend you try it with just water first to see what kind of pattern you get, then tweak from there until happy - at least that's what I did....

--------
Wow sorry, just came to the email area by accident and saw your question. Not sure why VAF didn't notify me of an email. But in anycase, take a standard propane torch for sweating copper solder joints (Lowes, HD) and heat up the little tube and slide it down. It only takes a little movement to get it right, and its in there with low temp solder. I had to tweak mine twice to get it in the sweet spot. Also make sure the top of the tube where the air blasts over it, is level if not just slightly angled in the direction of the air flow. A small jewelers file works good, but any will do. A little trial and error will make it work fantastic. Like I mentioned mine works at 10psi, which is nothing.....its like an HD gun at that pressure. And 20psi creates way too much overspray. Hope that helps. Good luck! Mani
 
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