First time priming, made a mess. Help me fix it?

Below you see the outcome of my first time priming with an HVLP sprayer.

I've made a mess of priming my first wing parts. I have a few thick runs and a few bald spots.


The question is, how do I best clean and prepare these parts for priming again?

I want to at least remove the thick runs. A friend suggested to soak parts overnight in some strong solvent (maybe MEK or Acetone) to get all the primer off, and re-shoot again.

Also, I would appreciate any advice on how to set up for priming. (I'm in the process of searching the forums and internet...)

Background: Done with a Harbor Freight HVLP gun, 40 psi, 1.5mm tip and Sherwin Williams DTM Wash Primer. The primer instructions say to prep parts with non-petroleum-based solvents and clean the sprayer afterwards with water (EDIT: On second read, the data sheet says to clean up with mineral spirits). I washed and lightly scuffed the parts with a dish Scotchbrite sponge and dish soap.

I propped the parts up against a wooden shipping crate and sprayed a first coat. That first coat came out clear. Puzzled, I waited 20 mins and realized I didn't mix the primer, so I mixed it and sprayed again. I then waited about 30 mins and saw some bald spots, which I sprayed again. Waiting about 8 hours, you see the result above.

Lessons for next time are that I'm putting on too much primer, and that the parts should be hung on wires since resting parts against a surface allows overspray to run and pool onto the parts.

Rattle cans are your friend!

Please meet Mr. Duplicolor self etching or Mrs. NAPA 7220.

Rocket scientists...

David

I'm lovin' the Duplicolor:



Fortunately, I'm also past the "it needs to be perfect" phase, thanks to a pep talk from Pete McCoy (thanks again for lunch, BTW!). Now, I always strive for perfection, but accept a little less. Anything safety-related needs to be 100 percent, but a few cosmetic boo-boos are not the end of the world.

SW primer

Dmitry
I am not familiar with SW DVM primer but I do use SW P60G2 in a HVLP gun.
The gun pressure sounds a bit high. Mine runs 25 psi.
Fan control is all the way out.
Paint control is 3/4 turn out.
The mix may be too thin or your spraying too much paint. You also need really good light to see.

I have found the easiest way to remove bad paint is scotch brite and lacquer thinner. It usually comes right off then you can wipe with a cloth or paper towel wet with lacquer thinner.

I've learned many hard lessons in the past month about painting. First, Aircraft Stripper from the box auto parts store will take off Sherwin Williams Wash primer just fine. It will also strip the nice urethane topcoat you thought you were ready to spray.

After much studying and practicing, here's what has worked well for me for setting the HVLP gun. The advice was given for setting most any HVLP gun and compensated for most conditions. I've found this to be true.

• Use the smallest tip you can. I've been spraying SW Wash primer with a 1.3.
• Squeeze the trigger (without paint) and then open the air regulator at the gun until it stops increasing and then tighten it back a very small amount.
• Open the fan to give a 6" cigar shape paint pattern at a distance of 6".
• Open the mixture until the above pattern starts to run on a vertical test surface after a quick on/off trigger squeeze. Then close the mixture down until it just barely doesn't run.
• Shoot at about 8" with a moderately fast pace with about 50% overlap.
• Practice A WHOLE BUNCH to get the speed and overlap and gun position and wet edge and lighting until you're happy.

Not enough practice and study = not happy.

Laying parts flat?

Wirejock, will try your gun settings. The SW DTM is nice (low VOC, easy cleanup - I hate smelly stuff). Sunk cost fallacy notwithstanding, I've plunked down $99 for a gallon of SW DTM so I think it's too early to give up on it

Thanks for the adivce on the Duplicolor, Dave. I'll see if I can get some, seems somewhat scarce.

For those that lay parts down flat for priming, do you prime one side at a time, let it dry and then flip?

Looks like O'Reilly auto parts has it in your neck of the woods.

This link may or may not work:
http://www.oreillyauto.com/site/c/detail/DPL0/DAP1690/N2543.oap

If not, search their site for "self etching primer". Strangely things like the part number and duplicolor failed to bring it up.

Shake well, serve with a nice wipe of the scotchbrite and acetone.

David

P.S.
Don't worry you'll still get to use the wash primer to do the inside of the control pushrods and other fun locations. I had to buy a $50 quart just for those.

priming

spaceflightmeow said:

Wirejock, will try your gun settings. The SW DTM is nice (low VOC, easy cleanup - I hate smelly stuff). Sunk cost fallacy notwithstanding, I've plunked down $99 for a gallon of SW DTM so I think it's too early to give up on it

Thanks for the adivce on the Duplicolor, Dave. I'll see if I can get some, seems somewhat scarce.

For those that lay parts down flat for priming, do you prime one side at a time, let it dry and then flip?

Click to expand...

Don't give up for sure. You'll get it.
The nice thing about P60G2 is it sets really fast so I lay parts on an old baby gate over two sawhorses. I flip them after the first coat.

Another tip. I move pretty fast over the parts in one direction then back over them 90 degrees in the other direction. It seems to help uniform coverage without runs.

Have you disassembled and cleaned your paint gun? I bought a few different ones from HF. The $14 ones had silicone gunk in them.

Yes, I did thoroughly disassemble and clean the gun with with odorless mineral spirits. First time using that stuff but it works as advertised. Will play with the settings tonight and report back.

pressure

29# at the gun with the trigger pulled is still on the high side. 20# works better for me. Run some laquer thinner thru the gun before and after painting.

spaceflightmeow said:

Wirejock, will try your gun settings. The SW DTM is nice (low VOC, easy cleanup - I hate smelly stuff). Sunk cost fallacy notwithstanding, I've plunked down $99 for a gallon of SW DTM so I think it's too early to give up on it

Thanks for the adivce on the Duplicolor, Dave. I'll see if I can get some, seems somewhat scarce.

For those that lay parts down flat for priming, do you prime one side at a time, let it dry and then flip?

Click to expand...

Wash primers are always pretty thin, like water. I shot some Sikkens (AKZO Nobel) wash primer and you just have to set the paint volume low.

Since it is already thin and may be near invisible when done, a red scotchbrite pad can quickly level it out. I can look pretty bad, still feel flat, and still do its job.

I hope you have already checked the efficacy of this primer for aluminum compared to chromate or chromate-free replacements.

Personally, I still use the chromate primer for bulk parts and alodine for small pieces and small batches. I know the corrosion effectiveness. I stick with it for consistency for the entire build.

Good luck, you will find the knack!

primer

Just for grins run down to NAPA and get the 7220 no clean up no mess and dries in 2 min. the other good thing is its rated for all top coats an self etching.
Bob

The SW works great when you get it figured out. Keep it a thin, light coat.

For info, very early on in my build I learned a valuable early builder tip. Make a light frame out of chicken wire. Spray all your parts at once. Touch them up with a rattle can as you drill, cut, clean and deburr them. Saves a ton of time in cleaning and set-up.

Nothing good comes out of a rattle can.

My new favorite primer is Akzo Nobel 2111. It's good stuff and doesn't come off.

I would not use Mineral spirits, it last too long. Use a good solvent Mek, or acetone

I washed all my aluminum parts with Pre-kote and then scrubbed them with a scotchbrite pads and then rinsed them with water.

Use a white primer it is easier to cover with bright colors on the plane such as yellows

My primer was mixes 50/50 and it sprayed beautiful
sherwin Williams

Jack

Success...but SW DTM is weak sauce

I had better luck spraying SW DTM again with the new gun settings. However, even after drying for a day, the stuff does not hold up well to scratches at all. Seems almost pointless without a topcoat. I cleaned the stuff off with lacquer thinner. Will respray with 7220 and see how that goes.

Primer

spaceflightmeow said:

I had better luck spraying SW DTM again with the new gun settings. However, even after drying for a day, the stuff does not hold up well to scratches at all. Seems almost pointless without a topcoat. I cleaned the stuff off with lacquer thinner. Will respray with 7220 and see how that goes.

Click to expand...

Not wanting to start a primer war but 7220 will scratch off too. I use it on small parts. Try Akzo or Sherwin Williams P60G2. Both are very thin, light and tough.