Second coat of Gunkote??

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[ARCHIVED THREAD] - Second coat of Gunkote??

Posted: 7/6/2014 12:08:11 PM EDT

Has anyone tried to apply a second coat of Gunkote over a baked first coat?

I followed all the steps anodizing first, K-phos light coat, then Gunkote. I even let the lowers sit in the sun for several hours before baking the Gunkote . The Gunkote is easy to come off as if it wasn't baked on enough. Now there are small spots of anodize showing when I was assembling the mag catch.

Using a toaster oven and it fluctuates as much as 60F. Maybe it didn't get hot enough to get binding. Don't want to put the lowers in the kitchen oven or the wife will shoot me.

I am thinking to rewash/scrub the lower with dish soap and then MEK rinse to get any hand oils off and airbrush the second coat and cook it at a higher temp.

Anyone try this before?

Posted: 7/6/2014 2:39:21 PM EDT

[#1]

If you baked the first coat hot enough and long enough, that coat should stay put. If you have some small spots that need touch up, hit it with an airbrush enough to cover the spots and finish it with a hair dryer on the spot. Depending how much paint you apply, spot finishing it should work fine.

Posted: 7/6/2014 4:48:30 PM EDT

[#2]

I suppose I should degrease again with soap/water and/or MEK just in case? If it wasn't hot enough, long enough, the MEK will most likely strip it. Perhaps only dish soap/water and dry in the oven low temp.

I'll try to touch up. Thanks for the input!

Posted: 7/6/2014 7:36:20 PM EDT

[#3]

You didn't degrease well enough or possibly the underlying finish wasn't fully dried. When there is trace oil the gunkote will flake off. Just degrease everything really thoroughly again and re spray. Gunkote will stick well to gunkote.

Posted: 7/6/2014 10:54:55 PM EDT

[#4]

After anodizing I let the part dry for several days. Then washed the part in dish soap to remove any residue from the anodizing process, rinsed with DI water and let dry. Then before the light coat of K-Phos, I preheated to 120F. I let the K-phos dry overnight before the GK. I'm sure no grease was on the part. I thread an AL rod to the pistol grip screw hole to handle the piece just to make sure it isn't compromised with oils from handling.

I was surprised that there was a couple of small specks of GK that came off after removing from the oven. Good to hear that GK sticks to GK and can be touched up. Perhaps I didn't heat it high/long enough in the toaster oven.

I'll degrease and try again. Thanks...

Posted: 7/8/2014 11:37:06 PM EDT

[#5]

Just some dish soap and a toothbrush removed some of the GK. Not that it flacked...it just lightened it to where the anodize would show through in some areas. Then used some MEK substitute on it and some more GK came off but not much. Makes me think I didn't heat it long enough and hot enough.

Cleaned the other 2 with the MEK sub and will let it dry overnight and spray a heavier layer of GK tomorrow, let them dry overnight again, then bake one more time hotter and longer.

I'll also get a new oven thermometer before cooking them.

Posted: 7/9/2014 11:45:23 PM EDT

[#6]

That sounds like you have it figured out. If it's oil it just flakes off. If it's not baked long enough it's like it stays wet. Good luck on the next run.

Also just remember to apply with thin passes. Brownells has a good video on the process but it should take you 5-6 passes for full coverage.

Posted: 7/10/2014 2:21:52 AM EDT

[#7]

Thanks... I airbrushed GK again today and definitely laid down more than the first time. Maybe too much. It seemed to look like powder residue on the sides so I laid down yet another coat and it evened it out mostly. No runs. We'll see what it looks like after baking tomorrow. I'm going to let it dry overnight.

I'll check out the Brownells clip to see if I can get any other tips before doing the next 2 lowers.

Posted: 7/10/2014 1:14:04 PM EDT

[#8]

Some dish soaps can leave residue.

I degrease everything with Acetone.
If the part is filthy, I bathe it in acetone and clean it with an AP brush.
Once clean, I let it sit completely covered in a tank of (clean) acetone for 20-30 minutes. Then a use an air compressor to blow off the acetone and then bake it for 20 minutes.

After that, I start my coating process.

Posted: 7/11/2014 12:12:27 AM EDT

[#9]

Quote History

Quoted:
Some dish soaps can leave residue.

I degrease everything with Acetone.
If the part is filthy, I bathe it in acetone and clean it with an AP brush.
Once clean, I let it sit completely covered in a tank of (clean) acetone for 20-30 minutes. Then a use an air compressor to blow off the acetone and then bake it for 20 minutes.

After that, I start my coating process.

View Quote

Possible the dish soap left residue. How hot do you bake after the acetone bath? I did a preheat to about 200F and let it cool down so I could just hold the aluminum rod I use as a handle threaded into the pistol grip screw hole...then sprayed the GK.

I just hit the worst of the lowers with brake cleaner and removed most of the last coat. Could see residue so I picked up some acetone and rinsed the residue off.

I'll shoot another coat of GK tomorrow, let dry for a day and bake the one lower and see how it comes out. Then progress to the others as I work on improving my procedure.

Thanks for the tips on prepping the part.

I'm afraid the compressor could possibly deposit water and oil vapor. I don't have a filter on my unit. We don't blow off parts at work for the same reason.

Posted: 7/11/2014 11:19:25 AM EDT

[#10]

Quote History

Quoted:

Possible the dish soap left residue. How hot do you bake after the acetone bath? I did a preheat to about 200F and let it cool down so I could just hold the aluminum rod I use as a handle threaded into the pistol grip screw hole...then sprayed the GK.

I just hit the worst of the lowers with brake cleaner and removed most of the last coat. Could see residue so I picked up some acetone and rinsed the residue off.

I'll shoot another coat of GK tomorrow, let dry for a day and bake the one lower and see how it comes out. Then progress to the others as I work on improving my procedure.

Thanks for the tips on prepping the part.

I'm afraid the compressor could possibly deposit water and oil vapor. I don't have a filter on my unit. We don't blow off parts at work for the same reason.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
Some dish soaps can leave residue.

I degrease everything with Acetone.
If the part is filthy, I bathe it in acetone and clean it with an AP brush.
Once clean, I let it sit completely covered in a tank of (clean) acetone for 20-30 minutes. Then a use an air compressor to blow off the acetone and then bake it for 20 minutes.

After that, I start my coating process.

Possible the dish soap left residue. How hot do you bake after the acetone bath? I did a preheat to about 200F and let it cool down so I could just hold the aluminum rod I use as a handle threaded into the pistol grip screw hole...then sprayed the GK.

I just hit the worst of the lowers with brake cleaner and removed most of the last coat. Could see residue so I picked up some acetone and rinsed the residue off.

I'll shoot another coat of GK tomorrow, let dry for a day and bake the one lower and see how it comes out. Then progress to the others as I work on improving my procedure.

Thanks for the tips on prepping the part.

I'm afraid the compressor could possibly deposit water and oil vapor. I don't have a filter on my unit. We don't blow off parts at work for the same reason.

I bake the clean parts at whatever temperature I will bake the coating at. So if I was using 3400 series Gunkote, I'd set the oven at 325 degrees and set my clean parts to bake for 20-30 minutes to let the left over acetone flash off from the nooks and cranies.

I think one of your problems may be is that your waiting for the paint to dry. I don't think Gunkote says you have to wait so long after coating to bake it (not that familiar with Gunkote). If your waiting 24 hours, you might be ruining the paints properties as it is exposed to air and not cured. If the process is similar to Cerakote, I stick it in the oven as soon as I'm done with painting my parts/batch.

If your afraid your air line might contain water, then let it air dry for 20-30 minutes in clean air. You should at least have an in-line filter on your spray gun to absorb water.

Posted: 7/11/2014 4:30:05 PM EDT

[#11]

You are correct. Parts are supposed to be baked right after spraying.

Also good point about moisture in the compressor line.

Posted: 7/11/2014 5:56:12 PM EDT

[#12]

Quote History

Quoted:

I bake the clean parts at whatever temperature I will bake the coating at. So if I was using 3400 series Gunkote, I'd set the oven at 325 degrees and set my clean parts to bake for 20-30 minutes to let the left over acetone flash off from the nooks and cranies.

I think one of your problems may be is that your waiting for the paint to dry. I don't think Gunkote says you have to wait so long after coating to bake it (not that familiar with Gunkote). If your waiting 24 hours, you might be ruining the paints properties as it is exposed to air and not cured. If the process is similar to Cerakote, I stick it in the oven as soon as I'm done with painting my parts/batch.

If your afraid your air line might contain water, then let it air dry for 20-30 minutes in clean air. You should at least have an in-line filter on your spray gun to absorb water.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
Some dish soaps can leave residue.

I degrease everything with Acetone.
If the part is filthy, I bathe it in acetone and clean it with an AP brush.
Once clean, I let it sit completely covered in a tank of (clean) acetone for 20-30 minutes. Then a use an air compressor to blow off the acetone and then bake it for 20 minutes.

After that, I start my coating process.

Possible the dish soap left residue. How hot do you bake after the acetone bath? I did a preheat to about 200F and let it cool down so I could just hold the aluminum rod I use as a handle threaded into the pistol grip screw hole...then sprayed the GK.

I just hit the worst of the lowers with brake cleaner and removed most of the last coat. Could see residue so I picked up some acetone and rinsed the residue off.

I'll shoot another coat of GK tomorrow, let dry for a day and bake the one lower and see how it comes out. Then progress to the others as I work on improving my procedure.

Thanks for the tips on prepping the part.

I'm afraid the compressor could possibly deposit water and oil vapor. I don't have a filter on my unit. We don't blow off parts at work for the same reason.

I bake the clean parts at whatever temperature I will bake the coating at. So if I was using 3400 series Gunkote, I'd set the oven at 325 degrees and set my clean parts to bake for 20-30 minutes to let the left over acetone flash off from the nooks and cranies.

I think one of your problems may be is that your waiting for the paint to dry. I don't think Gunkote says you have to wait so long after coating to bake it (not that familiar with Gunkote). If your waiting 24 hours, you might be ruining the paints properties as it is exposed to air and not cured. If the process is similar to Cerakote, I stick it in the oven as soon as I'm done with painting my parts/batch.

If your afraid your air line might contain water, then let it air dry for 20-30 minutes in clean air. You should at least have an in-line filter on your spray gun to absorb water.

I read from several that refinish professionally with GK that they let it dry overnight or longer and also KG had recommended this to one of them. It reduced the amount of vapor released in the baking process and it helped prevent any points of contact if the part was laid down to cook. Since I have to lay it down, I let it dry over night.

I believe the first time I baked it wasn't hot enough so the GK never cured. The second coat I had the part too hot and the GK stacked up on the part giving it a rough appearance. part of my learning curve I guess.
I just stripped the parts with brake cleaner and washed off with acetone. I'll have at it again today. I'm determined to get this done right.

I have a small compressor so I empty the air / water out after every use and remove the oiler and change out the airline before any airbrushing. I didn't have a moisture/oil trap or inline filter so I just ordered one. Now I can blow the part off when the filter comes in. I have several lowers to GK.

Thanks again for the input!

Posted: 7/11/2014 7:46:32 PM EDT

[#13]

What color are you using?

Posted: 7/11/2014 8:30:16 PM EDT

[#14]

2401F Matt Black

Posted: 7/12/2014 2:28:38 AM EDT

[#15]

I baked the third lower I had not one stripped again because the GK looked acceptable on it. Started to assemble and the trigger/hammer pins flaked the finish. I can actually flake it off with my fingernail once the flaking started. Guess I have to learn to AL oxide blast now.... :(

I resprayed the other 2 lowers, but now I'm second guessing if I stripped them enough. I did not get every bit of the previous GK off, so I suppose it's better to start again rather than take a chance that the GK won't stick. I never imagined I would have to fully degrease again after I anodized them. Only did a dish soap scrub. I'm learning the hard way I guess....

Posted: 7/12/2014 3:49:13 AM EDT

[#16]

Bad batch of paint?

Iv'e messed up a few projects practicing with various firearm finishes where I did not fully clean and prep my part before the coating, and it still came out pretty good.

Posted: 7/12/2014 12:22:23 PM EDT

[#17]

I'd like to blame it on the paint instead of my process techniques, but I only have one other experience with GK and that was years ago.

I oiled the part and used a paper towel instead of a rag to wipe the excess oil off, That's why the white filaments are seen. Otherwise the finish didn't look that bad.

When putting the mag catch on, there were a few spots where the finished flaked off and I hit it with brake cleaner and touched up with GK on a Q-tip and hit it with a heat gun. It blended in pretty good. Maybe I'll just do that with the exposed areas and call it good for now. Some day when I retire and have the time, I can go back and do the job right if I find the finish is falling off.

Posted: 7/13/2014 3:02:56 PM EDT

[#18]

Pic does look like there was contamination.

Dump everything in a container of acetone for 30-45 minutes.

Posted: 7/14/2014 12:55:58 AM EDT

[#19]

Soaked it for a good hour. Using a plastic putty knife I can flake more of the finish off. Knew I should have got the 1 gal acetone instead of the qt... I'm wondering if the K-phos is suspect or if the part had to be degreased after anodizing or if residual soap was left.

I wonder if an ultrasonic cleaner with acetone or something else would lift the GK off since it isn't stuck very well. Maybe I'm just looking for an excuse to get an ultrasonic cleaner... Either that or get a blast gun and media.

Posted: 7/14/2014 1:50:36 PM EDT

[#20]

If you have it flaking off you probably need to media blast it. Otherwise the base finish that is flaking will continue doing so. Properly applied gunkote is very durable and I have put parts that have been gunkoted in my ultrasonic cleaner with slip many times with no ill effects on finish.

You can also call kg for guidance. They are very helpful and may be able to trouble shoot your steps with you.

Posted: 7/15/2014 12:49:21 AM EDT

[#21]

Quote History

Quoted:
If you have it flaking off you probably need to media blast it. Otherwise the base finish that is flaking will continue doing so. Properly applied gunkote is very durable and I have put parts that have been gunkoted in my ultrasonic cleaner with slip many times with no ill effects on finish.

You can also call kg for guidance. They are very helpful and may be able to trouble shoot your steps with you.

View Quote

Darn, now I don't have an excuse to get one.... Picked up a blast gun with hopper feed today and started with some baking soda to see how it affected the finish. I soaked in a MEK substitute to loosen before blasting. Kept the anodizing and took off more of the GK, but it might not be aggressive enough. I'll give KG a call and see what tips they might have.... I'm sure they will have a few for a novice like me.

Set the soda blast at 90psi using a small 3gal compressor. Ran out of baking soda in the kitchen...

need to get some more...

Posted: 7/17/2014 6:53:19 PM EDT

[#22]

Just remember that you need to follow the instructions on the side of the gunkote. If you are going to blast it, you need to use 120 grit aluminum oxide at the correct pressure and not baking soda. Using baking soda will result in the problem you are having now and the finish will not adhere properly.

Posted: 8/17/2014 5:42:33 AM EDT

[#23]

I spoke to the owner of KG Ind about my issues with GK.

He suggested a light Al Oxide blast at about 20psi to slightly pit the surface and not remove the anodized surface. Then soak in acetone of 30 mins, remove and place in clean acetone another 30 mins. remove and put in oven to dry out the acetone before recoating w/o K-phos this time.

The lower that was not cured in the oven, I was able to get the GK off with a lot of work using Klean Strip Aircraft paint remover jell. It is similar to Jasco. Then I soda blasted at up to 100psi to knock off the rest of the GK.

The lower with the GK baked on the Klean Strip was less effective and I had better results knocking off the GK. The anodizing got removed with the Al Oxide.

To GK, I now had one lower with anodizing and a light blast and one with almost all the anodizing removed with a much heavier blast.

After baking the GK finish was much better than the last time. The acetone soak must have been needed after the anodizing and dish soap scrub I had previously prepped with.
The GK seemed to go on better with the anodized finish than with the non-anodized finish. The final result looks the same between the 2 none the less.

Posted: 8/17/2014 4:03:52 PM EDT

[#24]

Looks good. Glad you got it figured out. I really like gunkote and there customer service is exceptional.

Posted: 8/18/2014 11:14:06 AM EDT

[#25]

I told you that you probably need to let it soak in acetone

Posted: 8/19/2014 7:24:13 AM EDT

[#26]

Yes you did!

One more lower to re-GK. Should get that done this week.

Posted: 8/23/2014 3:50:14 PM EDT

[#27]

Last lower sprayed and baked. Much better than the first time. Soaked overnight in acetone this time. One small chip uot when the Hammer pin was inserted as seen on bottom pic.

Posted: 8/23/2014 8:42:54 PM EDT

[#28]

Looks good, except for the bullet button....but I can't hold you responsible for that

Posted: 8/25/2014 1:45:33 AM EDT

[#29]

Thanks....yeah its unavoidable unfortunately. I do have a registered Colt SP1 that doesn't have one of those dang things and I can use 30rd mags with it in CA as well.

[ARCHIVED THREAD] - Second coat of Gunkote??

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