Paint not withstanding abrasions

[lurtsman]

I have a great number of machines I'm painting. Using a primer and an industrial grade paint over that. (both are spray on) When I tried scraping it off, I had very little ability to scratch it with a thumb nail--but they kept chipping while I was carrying multiple machines in the truck despite careful packaging. The trick seemed to be that I was testing in areas that were hidden, while the chips occured in areas that are visible. What causes this difference? As far as I can tell Northwestern used something to coat their paint job that prevents other things from sticking. Therefore the primer can not create an effective bond when this sealant is present. When I tested on the inside of the machine, the sealant wasn't there, and the bond is excellent. On the outside, the paint easily comes off under fingernail pressure.

Solutions?

I prefer not to work with a paint stripper due to concerns over causing cancer as well as excessive investments in time and money to complete the job. Having an extra coat of paint further deters rust, so it wouldn't be a bad thing. Using a white primer I can turn red or orange into any lighter color -- the primer was very effective at that--it just couldn't adhere to whatever sealant northwestern used to protect these machines.

Please help  It's getting cold and I would like to get this job finished once and for all.

[Hillbilly]

lurts,  Several things could be causing this.

1) Primer surfacer can be sanded to hide imperfections in the paint or surface below it.  Primer sealer seals the surface below it so that various topcoats can stick to it. Such as painting with a lacquer based paint when the first coat was enamel.  Double check which kind of primer you are using. You may try using a sealer.

2) Look on your can of paint and see if it says hi-solids spray paint.  It is usually the industrial kind.  It uses less thinner or reducer to move the product so more "color" if you will, will land on the surface being painted. It will take a lot of regular spray paint to paint one machine. Very little hi solids.  The hi solids is usually more durable  hence the industrial word.

3) Dry time.  Paint dries from the outside in.  If the outside is dry but still wet underneath and you recoat too soon, then it takes a long time for the paint underneath to dry. So in essence several days could go by but the paint is still not dry where it is touching what is below it.  That would make it easier to scratch because it is not sticking to the substrate(metal) or the bottom coat below it.

4)  Have you put anything silicone based on the machines?  Such as Armor All? Paint will not stick to that.. Maybe there has been wax on it or something.  In that case get some Prep Solvent or Final Wash and clean really good before you start painting.  Basically it removes contaminants but normally seen with fish eyes in the top coat or fine cracks.

[Jax Snacks]

Did you sand the surface first?  Sanding will remove any glossiness.  I always use a higher grit (220) paper to prepare the surface and create a smooth finish as well.  Buy an electric sander if you don't have one.  Are the primer and paint from the same manufacturer?  Sometimes a primer and paint are not compatible.  I stopped using primer for that reason and just use Rustoleum (red) paint for the final finish.  I used to get stickers that were litterally peeling off with the red paint because it never adhered to the primer properly.

[lurtsman]

Rustoleum for primer and final paint.

We have high humidity over night and it doesn't get cold for very long. I used a significant amount of paint because I'm turning dark orange to tan. I strongly suspect #3 is a contributing reason--I had not considered how paint dries, and the directions said only a few minutes were needed between coats. With the weather out here it may do much better if I give it more time between coats to get the lower coat more ready before I adhere the next layers.

I cleaned the machines with water and scrubbing but I didn't sand. Is the glossiness a bad thing? The new color is not glossy and is pretty low key--but it appeals to the location.

1. I used this primer: http://www.rustoleum.com/CBGProduct.asp?pid=154

Most of the area I applied it to is painted. There are small rusted spots. Note last sentence : "Works with bare or previously painted metal."

I used this finish:

http://www.rustoleum.com/CBGProduct.asp?pid=95

On the can it says "Primers may be top coated immediately. Apply a second coat within 1 hour or after 48 hours."

2. I don't see the words "high solids", but the link would surely provide confirmation either way. My understanding is that this would qualify.

3. Highly possible. This morning I performed the test again and could not scrape the paint from the inside of the machine, but on the portion near the bottom that is covered when the coin access is closed and machine is locked--there I could easily scratch off the paint. The machines have been stored in pieces to allow better air flow. It's been 3, maybe 4 days since I painted that one. If this is an issue of drying, should I bringing them into the house once they are dry to handle? (1 hour or so)

4. I have not, but it's possible the previous seller did. I didn't think of it because my research didn't go beyond reading the cans. That makes sense as a possibility. Is there a simple test for this? (Simpler than running a control group, buying prep solvent and test painting then waiting a couple days to confirm/deny if this fixes it?

Over night it gets humid and cold, and these have been drying in the garage. (over night lows around 40 with 80% humidity)

[Hillbilly]

On the can it says "Primers may be top coated immediately. Apply a second coat within 1 hour or after 48 hours."

After reading this it sounds  it's narrowed down to 2 things.

  The time in between 1 hour and 48 hours is what I'm talking about with the dry time. After 1 hour it is dry enough to handle but not completely dry until 48 hours. So as long as your not painting longer than an hour you are OK.

  I  really think this is your problem. Try scuffing the paint after you wash it with a fine Scotchbrite pad or 600 grit sandpaper.  It will help if it is an adhesion problem.  Just use a product like I suggested to wipe them down or at least a tack cloth to remove dust. Humidity is what you are battling most.  It is also what is dulling your finish.  Try setting the objects on something that you can carry and then take them in the house when you are done.  Just be careful about your furnace being on and an explosion or something.

will.vend had a problem with humidity this summer and so did I. It kept raising on my machines. It was up around 90% at that time. So it may be just that.

Good luck.

[lurtsman]

Further reading:

"Preparation: Remove loose paint and rust with a wire brush or sandpaper. Lightly sand glossy surfaces. Clean with soap and water, rinse and let dry." Bold added for emphasis by me. Given the feed back here that seems to be the most likely culprit. humidity is @ 80%, the can says it can dry well up until 85%. I'll try the sand paper on a part, paint it giving 30 minutes after primer before I start light clear coats, and I'll bring it into the house to dry over night to keep it warmer and slightly less humid.

[lurtsman]

Hill, when you mention raising. My paint looked like it was erupting one time when I painted a lid. I was in a "wtf" mode for a while. Was that a humidity problem?

[will.vend]

will.vend had a problem with humidity this summer and so did I. It kept raising on my machines. It was up around 90% at that time. So it may be just that.

Good luck.

I started moving mine inside right after painting and it fixed this problem.

[lurtsman]

I'm going to go do two test pieces. I will sand and clean both. I will bring one into the garage after painting, and one into the house.

I will test both after wards.

PS. I've prepared a third with no scuffing that will also come inside. I'll upload the results after.

[Hillbilly]

Hill, when you mention raising. My paint looked like it was erupting one time when I painted a lid. I was in a "wtf" mode for a while. Was that a humidity problem?

Yes, That's a humidity problem.

How did the test piece do in the house?

[dperry]

Have you considered sandblasting?  Maybe some local places can do it on a per-piece basis.  I wonder what an auto painting place would charge you.

Maybe the old paint can be burned off with a propane torch?

Also, most American made machines powder coated?  Or are they sprayed?

[timberframe50]

You know I have never had this problem when painting a Vendstar. Painting plastic is so much easier.

[lurtsman]

I did a 24 hour test and they still scratched easily in all conditions. (scuffed or not, indoors or out) I did another test following a short trip to visit family. Have not tested the one in garage, the ones in the house are impervious to finger nails, showing only a minor scuff mark as I went at them again and again with the finger nail. Paint did not flake off. It appears to be a dry-time issue. Now that it's cold, I'll be keeping parts in the house after painting them.

[Hillbilly]

Glad you figured it out.  Looks like you'll just have to wait a week or so before re-assembly.