Primer Prep Problems

[JonJay]

Originally Posted by wirejock

Also, just in case, I mix P60G2 1 part primer to 2 parts catalyst. Very thin. Spray till only a hint of color can be seen. Usually two passes at 90°.

It works and I have done the same without any noticeable ill effects, adhesion issues etc... not 2:1, but certainly thinner. However....

I hate the thought of reducing the product solids and not following the manufacturers recommendations for mixing.

I found my Sharpe Platinum gun nozzle was the culprit. It is a fine nozzle and the thick primer was causing spattering and uneven solids dispersal. I changed over to a Sharpe Cobalt Primer gun and all was well. I could keep the specified 1:1 ration. However, if the can was opened, it may need thinned a bit down the line. I reserve the Platinun gun for top coating now.

Absolutely apply the coating as a “fog”’coat as you describe. 4 mils I believe is all it wants to be. I would have to read up on it again to be sure.

[jacoby]

Originally Posted by JonJay

Absolutely apply the coating as a “fog”’coat as you describe. 4 mils I believe is all it wants to be. I would have to read up on it again to be sure.

4 mils per coat is on the heavy side (approaching dripping and sagging) for most paints and primers that I've sprayed. Dry film thickness for the Akzo (which goes on thicker than the P60G2) at total opaque is around 0.5-0.75 mils. Wet is going to be closer to 1.5-2 mils.

I just looked at the TDS for the p60G2 and it should be sprayed at 1.3-2.6 mils wet. Dry is 0.2-0.4.

[jacoby]

Originally Posted by az_gila

Essentially that is what it did in the high humidity before it cured.

It may have been not dry enough and it didn't stick...

That's wild! I wonder if the aluminum was acting as a heat sink and letting water condense on it? I've sprayed in some pretty humid conditions and never had water pull out of the air.

[mulde35d]

Originally Posted by JonJay

All-Prep is used as a ?final wipe?. You don?t want to introduce water after. Water is the last thing I want on the surface of my part even with a thorough drying. Unless youre using distilled water, you will leave trace minerals and maybe even chemicals behind. Many get away with it, but it simply isn?t necessary to go through the process.
You will go through a lot of clean rags but Scotchbrite and then Prep-All is all that is needed. I am sorry, but Scotchbrite isn?t going to embed contaminates in the scratches. If your aluminum is so greasy and dirty that there is a concern, you could clean it, dry it, and then Scotchbrite, but I never do. Fingerprints, human oils, silicon, etc.... the Prep-All will take care of it after you Scotchbrite. Follow the directions on the Prep-All label. Simple.
You are not in a production environment so if you want to add steps you can, but the pros don?t. That?s why these products where developed. Prep and priming take a long time in the build process. Why not make it simple and easier with the right products? Your not washing dirty greasy dishes.

By the way, Dawn isn?t the same it used to be. They still make Classic Dawn, but it still is different and may have added scents and other chemicals. Also, it is much more concentrated than before. Not the same which could be why folks may have trouble using it like they did back in the day. Just a guess.

I am thinking a combination of the two methods may work best depending on the part. For the small parts I prefer to clean them in a water solution since I can keep them submerged and clean them all before removing the first one from the water and starting the oxidation process. Also, from a dust and inhalation hazard aspect I prefer to scuff them wet.

For these smaller parts I am thinking
1. Scuff with maroon scotchbrite pad in Bon Ami / water solution
2. rinse and wipe in clean water
3. blow dry and move into paint booth
4. Wipe / clean with Prep-All cleaner / degreaser

For larger parts that are more difficult to submerge I am going to try the following
1. Scuff with maroon scotchbrite pad on orbital sander (while wearing a respirator)
2. move into paint booth
3. Wipe / clean with Prep-All cleaner / degreaser (lots of paper towels and rags)

Kind of a hybrid of all the methods presented in the post. I look forward to seeing how the next spray session goes. I'll try to remember to take some pictures of the results and post them here.

[JonJay]

That will work just fine. Show us your results!

[Flyin'Bryan]

I had the same first reaction as Wirejock in post #13. He basically pointed out that one of the most common cause of lack of adhesion is failure to adequately remove the alclad layer, and if that is not the culprit, some other form of contamination or improper primer mix or weather (humidity) issue is usually to blame as others have discussed. I have experienced all of these.

Like John-G from post #2, I am an acetone guy, and it works well for me. What I noticed in your original post is that it seems that you were starting the scuffing process with the part already in the water solution at the very beginning of your process. If that is correct I don't think that you are removing enough of the alclad in some of those harder to reach/scuff areas on certain parts.

So, my process is to scuff it quite a bit while "dry," with the part on my bench or on a table. It makes a mess, but that's where the washing comes in. Then I wash the part in warm water with original Dawn formula detergent and a sponge to get rid of the visible scuffing residue as much as possible, and then I also rinse the parts in another bucket or two to ensure the detergent is removed. Then the part is air dried or sometimes I will "help" it with a paper towel or cloth - always being mindful of not touching the now-scuffed-and-washed part, except on extreme edges as necessary. Then I start the acetone cleaning process - usually with a clean microfiber rag, put on some rubber gloves, and I will reapply the acetone and keep going over all areas of the part as many times as necessary, checking that the amount of residual aluminum material on the rag starts to diminish, as reported by John-G.

Then, when the acetone cleaning is done, I prepare to prime the parts as soon as possible afterward. This has served me well when applying a number of different types of primer products on my airplane parts.

I will also add this - every time I engage in this process for a batch of various airplane parts that I need to prime, my hands and arms, and even my back end up quite sore much of the time because I also use a lot of elbow grease during this entire process. From my experience, I figure that if I am not sore from it then it probably that means I did not scuff or clean it enough.

Anyway, the point is to make certain you are scuffing enough of the alclad aluminum away, especially in those corners and under the flanges, etc., that are very easy to miss.

That's my experience and advice. Good luck and let us know how it turns out.

[TASEsq]

Originally Posted by fl-mike

Similarly, don't use syringes for measuring paint.

Hi Mike,

I have been using syringes to suck up the Stewart Systems primer for my parts and haven?t seen any issues as yet. Is the issue that the syringes may have silicone in the rubber part?

You got me wondering now if I?ve just been lucky...

[wirejock]

Originally Posted by TASEsq

Hi Mike,

I have been using syringes to suck up the Stewart Systems primer for my parts and haven?t seen any issues as yet. Is the issue that the syringes may have silicone in the rubber part?

You got me wondering now if I?ve just been lucky...

Yes, some feel the rubber is contaminated with silicone.

I've been using syringes for the entire build. 1 gallon P60G2, 1-1/2 quarts Jet Flex.
I did read posts early on about syringes and switched to rubberless for a while but neither has been an issue. I do clean them with lacquer thinner before first use if that makes any difference. I also label the inside plunger and outside so they can't get mixed up.

[benjam]

For these smaller parts I am thinking
1. Scuff with maroon scotchbrite pad in Bon Ami / water solution
2. rinse and wipe in clean water
3. blow dry and move into paint booth
4. Wipe / clean with Prep-All cleaner / degreaser

For larger parts that are more difficult to submerge I am going to try the following
1. Scuff with maroon scotchbrite pad on orbital sander (while wearing a respirator)
2. move into paint booth
3. Wipe / clean with Prep-All cleaner / degreaser (lots of paper towels and rags)

But then what? You've prepped the parts. What is the next step. (Pretend you're talking to some one with absolutely no idea of how to do this...)

[BillL]

Water is not just H2O. It has dissolved solids, so unless you are rinsing with de-ionized water, you could be leaving solid deposits there.


I have yet to see a picture of what your issues are. The log picture resolution is not good enough to see.