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Stewart Systems EkoPrime Test

skelrad

Well Known Member
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If anyone's curious, I wanted to see how EkoPrime would stand up to abuse on an acid etch only surface vs an acid etch plus Scotch Brite scuffed surface. I primed parts a week ago and primed a scrap piece with half prepped each way. 24 hours after the primer was put on (cool weather, so I'm positive the primer still had a ways to go to truly cure), I hit it with a sharp awl. The awl cut through the acid etch only side with minimal effort. While it cut through the scuffed surface to an extent, it was not nearly as noticeable. In the picture, the acid etch only portion is the top half (right under the word "awl") and the scuffed portion is the lower half of the metal.

I tested again at 6 days, figuring that the primer should have largely cured to it's long term hardness. The primer stood up much better to the awl on the acid etch surface. On the scuffed surface, the awl really just burnished the surface. It took a fair amount of aggressive scratching to get through to aluminum at all.

So all in all, given the ease of spraying the EkoPrime (water borne - no 2 parts to mix or wait for), I'm very pleased with it. Yes, I've beat up a few areas on the parts that are having to deal with my riveting education, but for the most part all primed surfaces have held of wonderfully to the abuse of a newbie builder. For all of the empennage I scuffed every single part while using the EkoEtch. I'll likely continue to do that just because I like the added toughness, but I'd have a hard time arguing with someone who just decided to clean parts and spray with an acid etch and not scuff at all. The primer seems to stick pretty well regardless. Obviously that's only for internal surfaces that won't see long-term abuse.
 

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This is good info, as the EcoEtch, red Scotchbrite prep then EcoPrime is essentially the method I'm now using.
 
Really interesting information and thanks for sharing.

I am waiting for the empennage and thought I would play around with some processes. I am working on painting/Priming and have got a sample kit from Stewart Systems. So far I like - but I haven't sprayed EkoPrime yet. Today I was playing with EkoClean and EkoEtch on a scrap piece of Aluminium.

I actually came on here to get an opinion of my testing. What I did was prepare two zones on the scrap piece, one I treated as per Stewart System's instructions (Clean then Etch) and then other I cleaned with MEK after EkoClean.

In both tests I cleaned until the EkoClean cloth was "rubbing clean". But I was shocked how dark the MEK cloth was afterwards. So it did lift further dirt off the surface.

So I am actually wondering, whether to clean with MEK and then EkoEtch, skipping the EkoClean step.

Given I am in Europe and the time now, I will stop, and I'll re-run my tests tomorrow, and spray with EkoPrime.
 
Bon Ami

Try something less toxic as a third.
Maroon scotchbrite, Bon Ami. Scrub to water break free surface. Dry. Paint within 2 hours.
 
Really interesting information and thanks for sharing.

I am waiting for the empennage and thought I would play around with some processes. I am working on painting/Priming and have got a sample kit from Stewart Systems. So far I like - but I haven't sprayed EkoPrime yet. Today I was playing with EkoClean and EkoEtch on a scrap piece of Aluminium.

I actually came on here to get an opinion of my testing. What I did was prepare two zones on the scrap piece, one I treated as per Stewart System's instructions (Clean then Etch) and then other I cleaned with MEK after EkoClean.

In both tests I cleaned until the EkoClean cloth was "rubbing clean". But I was shocked how dark the MEK cloth was afterwards. So it did lift further dirt off the surface.

So I am actually wondering, whether to clean with MEK and then EkoEtch, skipping the EkoClean step.

Given I am in Europe and the time now, I will stop, and I'll re-run my tests tomorrow, and spray with EkoPrime.

Not knowing anything about this process when I started, I bought both the EkoClean as well as the EkoEtch. After talking with Stewart, I learned that EkoEtch actually has detergents in it, so if you are going to use it along with schotch brite to etch, it'll clean the metal just fine. I use the etch and scotch brite, and after the recommended 3ish minutes of time for a part, I simply rinse it off with a garden hose. I usually use a rag to dry parts off just to speed things up, and very occasionally I'll get a SLIGHT amount of grey on the rag as I dry. After one swipe with the drying rag, no more grey though. In my first batch, I was the typical worried new guy, so pulled out some acetone to wipe the parts down more, but it really didn't pull anything else off the parts. Personally, from my limited experience, I would say you'd be overdoing it to clean with anything on top of using EkoEtch as long as you rinse thoroughly.

Just from my very limited experience, I am going to change how I do things in future prep. I was originally super worried about a great etch, so I spent a ridiculous amount of time scuffing with the scotch brite while using EkoEtch. Overkill in a big way and man, it's exhausting! For interior surfaces that aren't going to get abused, from what I've seen, the primer is going to stick just fine with minimal prep work.

When talking with Stewart, they actually said that in reality as long as you have clean metal after using EkoClean, the primer is going to stick well enough to do its job, even without any etching at all. This is for internal surfaces that will never be touched of course. That's one test I haven't done, but for internals, I think they're probably right. It's easy to get caught up in trying to find the absolute best solution to something and forget that the line between "good for the intended job" and "absolute best" is sometimes not even perceptible, but the "best" approach is 2x the effort. You have to decide where the line is for you. For me, I will lightly scuff as I clean parts with EkoEtch, but mostly I'll let the etch do its job. I'm really only lightly scuffing as I clean the parts, not the aggressive scuffing I was doing before for fear of primer peeling off when I looked at it wrong. For internal parts that will never see the light of day, the value in a perfectly, manually etched part is not big enough to justify the added effort and time in my opinion.

Maybe during my next priming day I'll test a piece that has been cleaned only, but with no etch. That's probably not a direction I want to go, but would be interesting to see the outcome and if the primer flakes off with bending or any kind of abuse.
 
Not knowing anything about this process when I started,

Exactly where I am. My first ever "squirt" with a spray gun was today for my trials. I have watched many youtube videos on gun setup etc. I'd say it went "OK" - I need to allow a bit longer between coats and I did spray too much on, so I got a few "High Corners" where the paint ran to. And I probably need to improve the lighting in the garage :D

Try something less toxic as a third.

I will do, living in Germany, everything was closed today, so I'll grab some Iso and Acetone from the DIY store tomorrow, and run a few more tests/practice sprays, before I attempt to paint the Vans Practice Flap Kit.

But just to share with the thread the results of today, in the attached photo from left to right I did the following. Far Left, exactly per Stewart Systems instructions (EkoClean/EkoEtch with Scotch Brite/Rinse/EkoPrime), centre left sample added a MEK clean (EkoClean/EkoEtch with Scotch Brite/Rinse/MEK Wipe/EkoPrime), centre right sample was Silicon Cleaner/mechanically etched with MEK and Scotch Brite, and the far right was cleaned with Silicone Cleaner, then cleaned with MEK and then etched with EkoEtch and Scotch Brite, rinsed with water.

I think the far right sample is probably marginally the best, (and it is marginal) but the left and centre left are about equal and just a tiny bit behind. The centre right, which was not chemically etched is the worst.

Maybe during my next priming day I'll test a piece that has been cleaned only, but with no etch.

I'll be interested in your results, for me it was the worst sample without the chemical etch, whether it's good enough though, I think is more a subjective thing, because I agree with you on the below quote.

It's easy to get caught up in trying to find the absolute best solution to something and forget that the line between "good for the intended job" and "absolute best" is sometimes not even perceptible, but the "best" approach is 2x the effort. You have to decide where the line is for you.
 

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Aluminum Oxide

The samples don't appear to be etching issues. To me they look contaminated. The fisheyes look like silicone or oil contamination. Keep silicone products in another city!

The enemy of adhesion on aluminum is aluminum oxide. Similar to the thin layer of rust that quickly forms on steel. It forms very quickly. Paint doesnt stick well to it. It's only a few microns thick and easily removed chemically or mechanically. Etching products are usually acid. They react and remove it while etching the surface so the paint can bite. Mechanically etching with scotchbrite and a cleanser works very well. Ajax and Comet work well but contain sodium hypoclorite (bleach). They can be used provided the surface is rinsed very well.
Solvents only clean the surface. They can't chemically remove the aluminum oxide layer. They have a place but there are safer choices for cleaning off contaminates. Coleman fuel or even Isopropyl alcohol work very well and far less dangerous to humans. Find a method you like to remove the aluminum oxide then paint within two hours before it reforms. Acid etch or scrub, wipe just before paint with a cleaner then shoot.

Test samples after cure by rubbing a piece of black Gorilla tape on the surface then rip it off. If the paint sticks, congratulations. That process is ok. If it rips the paint off, try something else.

Bottom line, harsh chemicals like MEK are not needed. Try to stay away from that stuff. Faster a solvent evaporates, the faster your body absorbs it. Save it for fuel tanks.
YMMV

I'll step off my soapbox now.:D
 
So I am actually wondering, whether to clean with MEK and then EkoEtch, skipping the EkoClean step.

This is intended as humor, PSA and best practice; ...What Larry (wirejock) said...

Leave the MEK in the can, on the back shelf, away from people -- your liver & brain will thank you and you'll have more processing capability for beer... :)

I think you'd be better served scuffing, then cleaning with Dawn (dishwashing detergent) and water rinse -- OR -- denatured alcohol then apply the etch+primer.
 
I stumbled across my test piece tonight, so grabbed the awl and scratched away again. It’s been a couple of months since I shot this primer. I can’t tell any difference at all between the acid etch only and acid plus scuffed surface. They are both equally tough (quite tough at this point!). If I didn’t know different, I’d say they were exactly the same preparation. I never did test the cleaned metal but no etch at all approach, but given what I see with these results, it may very well be completely adequate for interior surfaces, just like Stewart said. In the first few days I did see a difference in toughness between the prep methods, so it did appear that the less scuffing done meant poorer adhesion, at least initially. After curing completely, I just don’t see a difference though. The full blown scuffing approach takes twice as long and 10x the effort, just sayin. I am most definitely down shifting my scuffing from here on out!
 
Clean Only vs Scuff: Overall Priming Verdict

One more priming test piece just for fun: surface wiped down with acetone only vs light manual scuff and clean. This sample is less than 24 hours old and was sprayed in a 45 degree garage, so far less than ideal. I'm sure it's not fully cured, but I think it is enough to give a verdict and direct my future process.

The portion on the left is the scuffed part and the right half is the clean only part. There's no doubt that the scuffing makes a significant difference in the adhesion. That being said, I did some very aggressive scratching. Yes, the surface that was not scuffed definitely lifted easier compared to the other surface, but it still took a pretty significant amount of abuse. Once the primer came up, it did pull up in bigger chunks, as expected. I didn't take a picture, but I also tested how easily each side came up using acetone. EkoPrime is not solvent resistant, but the scuffed side still took a decent amount of rubbing with acetone to clean the surface. The cleaned only side softened up a lot faster and lifted in sheets.

My personal verdict from this test and the one before it: I used to do manual scuffing while acid etching. At least for EkoPrime, that's overkill. The acid etch alone (just using it to clean the surface, but not manual scuffing at the same time) is very nearly on par with manual scuffing, but I'd give the manual scuff a very slight lead if I had to choose. The cleaned but not scuffed parts surprised me by how well the primer still stuck. I would not take that approach on parts that are going to get some abuse, but for anything that just needs coverage and will be buttoned up without getting beat up, I wouldn't be concerned in the slightest about spraying EkoPrime directly on the cleaned surface with no scuffing. It performs far better than my self etching spray can primer does.

Given all of this, my process is going to change a bit since it sure looks like I was going overboard in prepping my surfaces. I really dislike the mess and process of acid etch/detergent (I used EkoEtch) because of the steps and time involved to etch and scuff, rinse, dry, etc. For most pieces, I'm no longer going to use the acid etch. I will lightly scuff, wipe down with acetone, and shoot primer. My manual scuffing is going to change as well. I really went at it before, and it not only took a lot of time, but was very labor intensive. My last tests were on pieces that were scuffed using a Scotch Brite pad on a random orbit sander. It looks like it barely scuffs the surface, but it takes the shine off of an entire wing skin in no time at all with no effort. I never scuffed parts before dimpling because I wasn't sure that the primer would hold up to the dimpling. That's not so. Scuffing before dimpling is 100x easier, and no concern at all. For parts that just get covered and sit there inside and never get touched, I'll scuff, but I won't lose sleep over hitting every square inch. Those parts would be absolutely fine with no scuff at all. That's exactly what Stewart Systems said when I asked. Do scuff any parts that you need the toughness factor for though.

One last thing about EkoPrime - When coupled with Devilbiss Dekups (worth every penny!), it becomes very nearly as convenient as a rattle can primer. I mixed up a batch of primer a month ago, meaning I added a tiny bit of water, and I didn't use all of it. A few ounces were poured in a small mason jar, and the rest stayed in the plastic Dekups container - all of the air pushed out and the plug put in. Yesterday I wanted to prime a single part, so just pulled out the Dekups container, gave it a little swirl to mix it all up, and primed the piece. Clean up is a 60 second task with hot water. The small mason jar is what I use with a Qtip to hit random areas. It's still good to use a month later. I love the waterborne primer for this reason. Extremely convenient (the lack of significant smell is really nice as well)!
 

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THanks for all this great testing. I’ve been using the EkoClean, EkoEtch, EkoPrime combo as well, and so far I love the ease of use. I got the 3M Performance Spray Gun with the PPS 2.0 system and it’s a breeze to clean. I work at a hangar with no running water, but bringing a small portable water source does the job for clean up. When I talked to the folks at Stewart Systems they thought it would be a good idea to switch to EkoPoly for the cockpit since I’m not planning on doing a paint coat in there. We’ll see where I end up with that.


The only issue I’ve had (being in a cold hangar), is that between session, the settling of the particulates is quite hard to mix. Are you having the same issues?

- Paolo
 
I agree - I'll definitely either switch to the EkoPoxy for the cockpit or use the EkoPrime and top coat it, just depending on what I decide to do in terms of how much I cover up with panels.

Yes, the EkoPrime definitely settles over time and is tough to mix. I use the Rockler paint lid mixing gizmo, which just ups the convenience factor even more. https://www.rockler.com/mixing-mate-paint-lid-gallon-size-stir-pour-and-store?gclid=CjwKCAiAn5uOBhADEiwA_pZwcBq9ZgY7B7YACAvMydY-k5CUSKbBVFt0CZduRUO_kcPMKXz5WeeleBoCokUQAvD_BwE

It is still really hard to get started once the solids have settled. I use the mixing paddle on the Rockler and just slowly drop it down against the solids as I mix. If I tried to just power through the sludge I think it would break.
 
It is still really hard to get started once the solids have settled. I use the mixing paddle on the Rockler and just slowly drop it down against the solids as I mix. If I tried to just power through the sludge I think it would break.

Yup. I have the same. One of these days I’m convinced the shaft is going to snap, but so far so good!
 
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